| Message ID | 20231030142658.182193-13-kwolf@redhat.com |
|---|---|
| State | New |
| Headers | show |
| Series | qdev: Make array properties user accessible again | expand |
On 30/10/2023 14:26, Kevin Wolf wrote: > Until now, array properties are actually implemented with a hack that > uses multiple properties on the QOM level: a static "foo-len" property > and after it is set, dynamically created "foo[i]" properties. > > In external interfaces (-device on the command line and device_add in > QMP), this interface was broken by commit f3558b1b ('qdev: Base object > creation on QDict rather than QemuOpts') because QDicts are unordered > and therefore it could happen that QEMU tried to set the indexed > properties before setting the length, which fails and effectively makes > array properties inaccessible. In particular, this affects the 'ports' > property of the 'rocker' device, which used to be configured like this: > > -device rocker,len-ports=2,ports[0]=dev0,ports[1]=dev1 > > This patch reworks the external interface so that instead of using a > separate top-level property for the length and for each element, we use > a single true array property that accepts a list value. In the external > interfaces, this is naturally expressed as a JSON list and makes array > properties accessible again. The new syntax looks like this: > > -device '{"driver":"rocker","ports":["dev0","dev1"]}' > > Creating an array property on the command line without using JSON format > is currently not possible. This could be fixed by switching from > QemuOpts to a keyval parser, which however requires consideration of the > compatibility implications. > > All internal users of devices with array properties go through > qdev_prop_set_array() at this point, so updating it takes care of all of > them. Is it possible to find a suitable place in the documentation to show how the new array syntax is used with -device on the command line? The description above is really useful, but I can see this being quite hard for users to find if it is only documented in the commit message. > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1090 > Fixes: f3558b1b763683bb877f7dd5b282469cdadc65c3 > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > include/hw/qdev-properties.h | 59 +++++---- > hw/core/qdev-properties.c | 224 ++++++++++++++++++++++------------- > 2 files changed, 183 insertions(+), 100 deletions(-) > > diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h > index 7fa2fdb7c9..cac752bade 100644 > --- a/include/hw/qdev-properties.h > +++ b/include/hw/qdev-properties.h > @@ -1,7 +1,10 @@ > #ifndef QEMU_QDEV_PROPERTIES_H > #define QEMU_QDEV_PROPERTIES_H > > +#include <stdalign.h> > + > #include "hw/qdev-core.h" > +#include "qapi/visitor.h" > > /** > * Property: > @@ -61,7 +64,7 @@ extern const PropertyInfo qdev_prop_size; > extern const PropertyInfo qdev_prop_string; > extern const PropertyInfo qdev_prop_on_off_auto; > extern const PropertyInfo qdev_prop_size32; > -extern const PropertyInfo qdev_prop_arraylen; > +extern const PropertyInfo qdev_prop_array; > extern const PropertyInfo qdev_prop_link; > > #define DEFINE_PROP(_name, _state, _field, _prop, _type, ...) { \ > @@ -115,8 +118,6 @@ extern const PropertyInfo qdev_prop_link; > .bitmask = (_bitmask), \ > .set_default = false) > > -#define PROP_ARRAY_LEN_PREFIX "len-" > - > /** > * DEFINE_PROP_ARRAY: > * @_name: name of the array > @@ -127,28 +128,46 @@ extern const PropertyInfo qdev_prop_link; > * @_arrayprop: PropertyInfo defining what property the array elements have > * @_arraytype: C type of the array elements > * > - * Define device properties for a variable-length array _name. A > - * static property "len-arrayname" is defined. When the device creator > - * sets this property to the desired length of array, further dynamic > - * properties "arrayname[0]", "arrayname[1]", ... are defined so the > - * device creator can set the array element values. Setting the > - * "len-arrayname" property more than once is an error. > + * Define device properties for a variable-length array _name. The array is > + * represented as a list in the visitor interface. > * > - * When the array length is set, the @_field member of the device > + * @_arraytype is required to be movable with memcpy() and to have an alignment > + * such that it can be stored at GenericList.padding. > + * > + * When the array property is set, the @_field member of the device > * struct is set to the array length, and @_arrayfield is set to point > - * to (zero-initialised) memory allocated for the array. For a zero > - * length array, @_field will be set to 0 and @_arrayfield to NULL. > + * to the memory allocated for the array. > + * > * It is the responsibility of the device deinit code to free the > * @_arrayfield memory. > */ > -#define DEFINE_PROP_ARRAY(_name, _state, _field, \ > - _arrayfield, _arrayprop, _arraytype) \ > - DEFINE_PROP((PROP_ARRAY_LEN_PREFIX _name), \ > - _state, _field, qdev_prop_arraylen, uint32_t, \ > - .set_default = true, \ > - .defval.u = 0, \ > - .arrayinfo = &(_arrayprop), \ > - .arrayfieldsize = sizeof(_arraytype), \ > +#define DEFINE_PROP_ARRAY(_name, _state, _field, \ > + _arrayfield, _arrayprop, _arraytype) \ > + DEFINE_PROP(_name, _state, _field, qdev_prop_array, uint32_t, \ > + .set_default = true, \ > + .defval.u = 0, \ > + .arrayinfo = &(_arrayprop), \ > + /* \ > + * set_prop_array() temporarily stores elements at \ > + * GenericList.padding. Make sure that this has the \ > + * right alignment for @_arraytype. \ > + * \ > + * Hack: In this place, neither static assertions work \ > + * nor is a statement expression allowed. This \ > + * abomination of an expression works because inside \ > + * the declaration of a dummy struct, static assertions \ > + * are possible. Using the comma operator causes \ > + * warnings about an unused value and casting to void \ > + * makes the expression not constant in gcc, so instead \ > + * of ignoring the first part, make it evaluate to 0 \ > + * and add it to the actual result. \ > + */ \ > + .arrayfieldsize = (!sizeof(struct { \ > + QEMU_BUILD_BUG_ON( \ > + !QEMU_IS_ALIGNED(sizeof(GenericList), \ > + alignof(_arraytype))); \ > + int dummy; \ > + }) + sizeof(_arraytype)), \ > .arrayoffset = offsetof(_state, _arrayfield)) > > #define DEFINE_PROP_LINK(_name, _state, _field, _type, _ptr_type) \ > diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c > index fb4daba799..4f3e1152be 100644 > --- a/hw/core/qdev-properties.c > +++ b/hw/core/qdev-properties.c > @@ -546,98 +546,174 @@ const PropertyInfo qdev_prop_size32 = { > > /* --- support for array properties --- */ > > -/* Used as an opaque for the object properties we add for each > - * array element. Note that the struct Property must be first > - * in the struct so that a pointer to this works as the opaque > - * for the underlying element's property hooks as well as for > - * our own release callback. > +/* > + * Given an array property @parent_prop in @obj, return a Property for a > + * specific element of the array. Arrays are backed by an uint32_t length field > + * and an element array. @elem points at an element in this element array. > */ > -typedef struct { > - struct Property prop; > - char *propname; > - ObjectPropertyRelease *release; > -} ArrayElementProperty; > - > -/* object property release callback for array element properties: > - * we call the underlying element's property release hook, and > - * then free the memory we allocated when we added the property. > +static Property array_elem_prop(Object *obj, Property *parent_prop, > + const char *name, char *elem) > +{ > + return (Property) { > + .info = parent_prop->arrayinfo, > + .name = name, > + /* > + * This ugly piece of pointer arithmetic sets up the offset so > + * that when the underlying release hook calls qdev_get_prop_ptr > + * they get the right answer despite the array element not actually > + * being inside the device struct. > + */ > + .offset = (uintptr_t)elem - (uintptr_t)obj, > + }; > +} > + > +/* > + * Object property release callback for array properties: We call the > + * underlying element's property release hook for each element. > + * > + * Note that it is the responsibility of the individual device's deinit > + * to free the array proper. > */ > -static void array_element_release(Object *obj, const char *name, void *opaque) > +static void release_prop_array(Object *obj, const char *name, void *opaque) > { > - ArrayElementProperty *p = opaque; > - if (p->release) { > - p->release(obj, name, opaque); > + Property *prop = opaque; > + uint32_t *alenptr = object_field_prop_ptr(obj, prop); > + void **arrayptr = (void *)obj + prop->arrayoffset; > + char *elem = *arrayptr; > + int i; > + > + if (!prop->arrayinfo->release) { > + return; > + } > + > + for (i = 0; i < *alenptr; i++) { > + Property elem_prop = array_elem_prop(obj, prop, name, elem); > + prop->arrayinfo->release(obj, NULL, &elem_prop); > + elem += prop->arrayfieldsize; > } > - g_free(p->propname); > - g_free(p); > } > > -static void set_prop_arraylen(Object *obj, Visitor *v, const char *name, > - void *opaque, Error **errp) > +/* > + * Setter for an array property. This sets both the array length (which > + * is technically the property field in the object) and the array itself > + * (a pointer to which is stored in the additional field described by > + * prop->arrayoffset). > + */ > +static void set_prop_array(Object *obj, Visitor *v, const char *name, > + void *opaque, Error **errp) > { > - /* Setter for the property which defines the length of a > - * variable-sized property array. As well as actually setting the > - * array-length field in the device struct, we have to create the > - * array itself and dynamically add the corresponding properties. > - */ > + ERRP_GUARD(); > Property *prop = opaque; > uint32_t *alenptr = object_field_prop_ptr(obj, prop); > void **arrayptr = (void *)obj + prop->arrayoffset; > - void *eltptr; > - const char *arrayname; > - int i; > + GenericList *list, *elem, *next; > + const size_t list_elem_size = sizeof(*list) + prop->arrayfieldsize; > + char *elemptr; > + bool ok = true; > > if (*alenptr) { > error_setg(errp, "array size property %s may not be set more than once", > name); > return; > } > - if (!visit_type_uint32(v, name, alenptr, errp)) { > + > + if (!visit_start_list(v, name, &list, list_elem_size, errp)) { > return; > } > - if (!*alenptr) { > + > + /* Read the whole input into a temporary list */ > + elem = list; > + while (elem) { > + Property elem_prop = array_elem_prop(obj, prop, name, elem->padding); > + prop->arrayinfo->set(obj, v, NULL, &elem_prop, errp); > + if (*errp) { > + ok = false; > + goto out_obj; > + } > + if (*alenptr == INT_MAX) { > + error_setg(errp, "array is too big"); > + return; > + } > + (*alenptr)++; > + elem = visit_next_list(v, elem, list_elem_size); > + } > + > + ok = visit_check_list(v, errp); > +out_obj: > + visit_end_list(v, (void**) &list); > + > + if (!ok) { > + for (elem = list; elem; elem = next) { > + Property elem_prop = array_elem_prop(obj, prop, name, > + elem->padding); > + if (prop->arrayinfo->release) { > + prop->arrayinfo->release(obj, NULL, &elem_prop); > + } > + next = elem->next; > + g_free(elem); > + } > return; > } > > - /* DEFINE_PROP_ARRAY guarantees that name should start with this prefix; > - * strip it off so we can get the name of the array itself. > + /* > + * Now that we know how big the array has to be, move the data over to a > + * linear array and free the temporary list. > */ > - assert(strncmp(name, PROP_ARRAY_LEN_PREFIX, > - strlen(PROP_ARRAY_LEN_PREFIX)) == 0); > - arrayname = name + strlen(PROP_ARRAY_LEN_PREFIX); > + *arrayptr = g_malloc_n(*alenptr, prop->arrayfieldsize); > + elemptr = *arrayptr; > + for (elem = list; elem; elem = next) { > + memcpy(elemptr, elem->padding, prop->arrayfieldsize); > + elemptr += prop->arrayfieldsize; > + next = elem->next; > + g_free(elem); > + } > +} > > - /* Note that it is the responsibility of the individual device's deinit > - * to free the array proper. > - */ > - *arrayptr = eltptr = g_malloc0(*alenptr * prop->arrayfieldsize); > - for (i = 0; i < *alenptr; i++, eltptr += prop->arrayfieldsize) { > - char *propname = g_strdup_printf("%s[%d]", arrayname, i); > - ArrayElementProperty *arrayprop = g_new0(ArrayElementProperty, 1); > - arrayprop->release = prop->arrayinfo->release; > - arrayprop->propname = propname; > - arrayprop->prop.info = prop->arrayinfo; > - arrayprop->prop.name = propname; > - /* This ugly piece of pointer arithmetic sets up the offset so > - * that when the underlying get/set hooks call qdev_get_prop_ptr > - * they get the right answer despite the array element not actually > - * being inside the device struct. > - */ > - arrayprop->prop.offset = eltptr - (void *)obj; > - assert(object_field_prop_ptr(obj, &arrayprop->prop) == eltptr); > - object_property_add(obj, propname, > - arrayprop->prop.info->name, > - field_prop_getter(arrayprop->prop.info), > - field_prop_setter(arrayprop->prop.info), > - array_element_release, > - arrayprop); > +static void get_prop_array(Object *obj, Visitor *v, const char *name, > + void *opaque, Error **errp) > +{ > + ERRP_GUARD(); > + Property *prop = opaque; > + uint32_t *alenptr = object_field_prop_ptr(obj, prop); > + void **arrayptr = (void *)obj + prop->arrayoffset; > + char *elem = *arrayptr; > + GenericList *list; > + const size_t list_elem_size = sizeof(*list) + prop->arrayfieldsize; > + int i; > + bool ok; > + > + if (!visit_start_list(v, name, &list, list_elem_size, errp)) { > + return; > } > + > + for (i = 0; i < *alenptr; i++) { > + Property elem_prop = array_elem_prop(obj, prop, name, elem); > + prop->arrayinfo->get(obj, v, NULL, &elem_prop, errp); > + if (*errp) { > + goto out_obj; > + } > + elem += prop->arrayfieldsize; > + } > + > + /* visit_check_list() can only fail for input visitors */ > + ok = visit_check_list(v, errp); > + assert(ok); > + > +out_obj: > + visit_end_list(v, (void**) &list); > } > > -const PropertyInfo qdev_prop_arraylen = { > - .name = "uint32", > - .get = get_uint32, > - .set = set_prop_arraylen, > - .set_default_value = qdev_propinfo_set_default_value_uint, > +static void default_prop_array(ObjectProperty *op, const Property *prop) > +{ > + object_property_set_default_list(op); > +} > + > +const PropertyInfo qdev_prop_array = { > + .name = "list", > + .get = get_prop_array, > + .set = set_prop_array, > + .release = release_prop_array, > + .set_default_value = default_prop_array, > }; > > /* --- public helpers --- */ > @@ -743,20 +819,8 @@ void qdev_prop_set_enum(DeviceState *dev, const char *name, int value) > > void qdev_prop_set_array(DeviceState *dev, const char *name, QList *values) > { > - const QListEntry *entry; > - g_autofree char *prop_len = g_strdup_printf("len-%s", name); > - unsigned i = 0; > - > - object_property_set_int(OBJECT(dev), prop_len, qlist_size(values), > - &error_abort); > - > - QLIST_FOREACH_ENTRY(values, entry) { > - g_autofree char *prop_idx = g_strdup_printf("%s[%u]", name, i); > - object_property_set_qobject(OBJECT(dev), prop_idx, entry->value, > - &error_abort); > - i++; > - } > - > + object_property_set_qobject(OBJECT(dev), name, QOBJECT(values), > + &error_abort); > qobject_unref(values); > } ATB, Mark.
Am 30.10.2023 um 21:48 hat Mark Cave-Ayland geschrieben: > On 30/10/2023 14:26, Kevin Wolf wrote: > > > Until now, array properties are actually implemented with a hack that > > uses multiple properties on the QOM level: a static "foo-len" property > > and after it is set, dynamically created "foo[i]" properties. > > > > In external interfaces (-device on the command line and device_add in > > QMP), this interface was broken by commit f3558b1b ('qdev: Base object > > creation on QDict rather than QemuOpts') because QDicts are unordered > > and therefore it could happen that QEMU tried to set the indexed > > properties before setting the length, which fails and effectively makes > > array properties inaccessible. In particular, this affects the 'ports' > > property of the 'rocker' device, which used to be configured like this: > > > > -device rocker,len-ports=2,ports[0]=dev0,ports[1]=dev1 > > > > This patch reworks the external interface so that instead of using a > > separate top-level property for the length and for each element, we use > > a single true array property that accepts a list value. In the external > > interfaces, this is naturally expressed as a JSON list and makes array > > properties accessible again. The new syntax looks like this: > > > > -device '{"driver":"rocker","ports":["dev0","dev1"]}' > > > > Creating an array property on the command line without using JSON format > > is currently not possible. This could be fixed by switching from > > QemuOpts to a keyval parser, which however requires consideration of the > > compatibility implications. > > > > All internal users of devices with array properties go through > > qdev_prop_set_array() at this point, so updating it takes care of all of > > them. > > Is it possible to find a suitable place in the documentation to show > how the new array syntax is used with -device on the command line? The > description above is really useful, but I can see this being quite > hard for users to find if it is only documented in the commit message. Actually, it seems that the documentation doesn't explicitly mention JSON syntax for command line options anywhere. Support for it is quite widespread meanwhile. I can see it for at least: -audiodev -blockdev -compat -device -display -netdev -object In qemu-storage-daemon, it's additionally supported for: --export --monitor --nbd-server I think the manpage should at least mention for each of these options that they support JSON. Ideally, we'd then have a generic section that describes the mapping between JSON and human syntax, but unfortunately, the human oriented parsers differ quite a lot between these options, so there is nothing we can describe and that is valid for all options. So maybe things like "Specifying values for list properties is only possible with JSON syntax" must be specified for each option where it applies. Kevin
Kevin Wolf <kwolf@redhat.com> writes: > Until now, array properties are actually implemented with a hack that > uses multiple properties on the QOM level: a static "foo-len" property > and after it is set, dynamically created "foo[i]" properties. > > In external interfaces (-device on the command line and device_add in > QMP), this interface was broken by commit f3558b1b ('qdev: Base object > creation on QDict rather than QemuOpts') because QDicts are unordered > and therefore it could happen that QEMU tried to set the indexed > properties before setting the length, which fails and effectively makes > array properties inaccessible. In particular, this affects the 'ports' > property of the 'rocker' device, which used to be configured like this: > > -device rocker,len-ports=2,ports[0]=dev0,ports[1]=dev1 > > This patch reworks the external interface so that instead of using a > separate top-level property for the length and for each element, we use > a single true array property that accepts a list value. In the external > interfaces, this is naturally expressed as a JSON list and makes array > properties accessible again. The new syntax looks like this: > > -device '{"driver":"rocker","ports":["dev0","dev1"]}' > > Creating an array property on the command line without using JSON format > is currently not possible. This could be fixed by switching from > QemuOpts to a keyval parser, which however requires consideration of the > compatibility implications. > > All internal users of devices with array properties go through > qdev_prop_set_array() at this point, so updating it takes care of all of > them. > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1090 > Fixes: f3558b1b763683bb877f7dd5b282469cdadc65c3 > Signed-off-by: Kevin Wolf <kwolf@redhat.com> > --- > include/hw/qdev-properties.h | 59 +++++---- > hw/core/qdev-properties.c | 224 ++++++++++++++++++++++------------- > 2 files changed, 183 insertions(+), 100 deletions(-) > > diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h > index 7fa2fdb7c9..cac752bade 100644 > --- a/include/hw/qdev-properties.h > +++ b/include/hw/qdev-properties.h > @@ -1,7 +1,10 @@ > #ifndef QEMU_QDEV_PROPERTIES_H > #define QEMU_QDEV_PROPERTIES_H > > +#include <stdalign.h> > + First use of this header in QEMU. You need it for macro alignof(). We use GCC extension __alignof__ elsewhere. Recommend to stick to that. > #include "hw/qdev-core.h" > +#include "qapi/visitor.h" This one you need just for GenericList. Might want to move GenericList into its own header. > > /** > * Property: > @@ -61,7 +64,7 @@ extern const PropertyInfo qdev_prop_size; > extern const PropertyInfo qdev_prop_string; > extern const PropertyInfo qdev_prop_on_off_auto; > extern const PropertyInfo qdev_prop_size32; > -extern const PropertyInfo qdev_prop_arraylen; > +extern const PropertyInfo qdev_prop_array; > extern const PropertyInfo qdev_prop_link; > > #define DEFINE_PROP(_name, _state, _field, _prop, _type, ...) { \ > @@ -115,8 +118,6 @@ extern const PropertyInfo qdev_prop_link; > .bitmask = (_bitmask), \ > .set_default = false) > > -#define PROP_ARRAY_LEN_PREFIX "len-" > - > /** > * DEFINE_PROP_ARRAY: > * @_name: name of the array > @@ -127,28 +128,46 @@ extern const PropertyInfo qdev_prop_link; > * @_arrayprop: PropertyInfo defining what property the array elements have > * @_arraytype: C type of the array elements > * > - * Define device properties for a variable-length array _name. A > - * static property "len-arrayname" is defined. When the device creator > - * sets this property to the desired length of array, further dynamic > - * properties "arrayname[0]", "arrayname[1]", ... are defined so the > - * device creator can set the array element values. Setting the > - * "len-arrayname" property more than once is an error. > + * Define device properties for a variable-length array _name. The array is > + * represented as a list in the visitor interface. > * > - * When the array length is set, the @_field member of the device > + * @_arraytype is required to be movable with memcpy() and to have an alignment > + * such that it can be stored at GenericList.padding. Please wrap like this for readability: * Define device properties for a variable-length array _name. The * array is represented as a list in the visitor interface. * * @_arraytype is required to be movable with memcpy() and to have an * alignment such that it can be stored at GenericList.padding. > + * > + * When the array property is set, the @_field member of the device > * struct is set to the array length, and @_arrayfield is set to point > - * to (zero-initialised) memory allocated for the array. For a zero > - * length array, @_field will be set to 0 and @_arrayfield to NULL. > + * to the memory allocated for the array. > + * > * It is the responsibility of the device deinit code to free the > * @_arrayfield memory. > */ > -#define DEFINE_PROP_ARRAY(_name, _state, _field, \ > - _arrayfield, _arrayprop, _arraytype) \ > - DEFINE_PROP((PROP_ARRAY_LEN_PREFIX _name), \ > - _state, _field, qdev_prop_arraylen, uint32_t, \ > - .set_default = true, \ > - .defval.u = 0, \ > - .arrayinfo = &(_arrayprop), \ > - .arrayfieldsize = sizeof(_arraytype), \ > +#define DEFINE_PROP_ARRAY(_name, _state, _field, \ > + _arrayfield, _arrayprop, _arraytype) \ > + DEFINE_PROP(_name, _state, _field, qdev_prop_array, uint32_t, \ > + .set_default = true, \ > + .defval.u = 0, \ > + .arrayinfo = &(_arrayprop), \ > + /* \ > + * set_prop_array() temporarily stores elements at \ > + * GenericList.padding. Make sure that this has the \ > + * right alignment for @_arraytype. \ > + * \ > + * Hack: In this place, neither static assertions work \ > + * nor is a statement expression allowed. This \ > + * abomination of an expression works because inside \ > + * the declaration of a dummy struct, static assertions \ > + * are possible. Using the comma operator causes \ > + * warnings about an unused value and casting to void \ > + * makes the expression not constant in gcc, so instead \ > + * of ignoring the first part, make it evaluate to 0 \ > + * and add it to the actual result. \ > + */ \ > + .arrayfieldsize = (!sizeof(struct { \ > + QEMU_BUILD_BUG_ON( \ > + !QEMU_IS_ALIGNED(sizeof(GenericList), \ > + alignof(_arraytype))); \ > + int dummy; \ > + }) + sizeof(_arraytype)), \ > .arrayoffset = offsetof(_state, _arrayfield)) > > #define DEFINE_PROP_LINK(_name, _state, _field, _type, _ptr_type) \ > diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c > index fb4daba799..4f3e1152be 100644 > --- a/hw/core/qdev-properties.c > +++ b/hw/core/qdev-properties.c > @@ -546,98 +546,174 @@ const PropertyInfo qdev_prop_size32 = { > > /* --- support for array properties --- */ > > -/* Used as an opaque for the object properties we add for each > - * array element. Note that the struct Property must be first > - * in the struct so that a pointer to this works as the opaque > - * for the underlying element's property hooks as well as for > - * our own release callback. > +/* > + * Given an array property @parent_prop in @obj, return a Property for a > + * specific element of the array. Arrays are backed by an uint32_t length field > + * and an element array. @elem points at an element in this element array. > */ Please wrap like this for readability: /* * Given an array property @parent_prop in @obj, return a Property for * a specific element of the array. Arrays are backed by an uint32_t * length field and an element array. @elem points at an element in * this element array. */ > -typedef struct { > - struct Property prop; > - char *propname; > - ObjectPropertyRelease *release; > -} ArrayElementProperty; > - > -/* object property release callback for array element properties: > - * we call the underlying element's property release hook, and > - * then free the memory we allocated when we added the property. > +static Property array_elem_prop(Object *obj, Property *parent_prop, > + const char *name, char *elem) > +{ > + return (Property) { > + .info = parent_prop->arrayinfo, > + .name = name, > + /* > + * This ugly piece of pointer arithmetic sets up the offset so > + * that when the underlying release hook calls qdev_get_prop_ptr > + * they get the right answer despite the array element not actually > + * being inside the device struct. > + */ > + .offset = (uintptr_t)elem - (uintptr_t)obj, > + }; > +} > + > +/* > + * Object property release callback for array properties: We call the > + * underlying element's property release hook for each element. > + * > + * Note that it is the responsibility of the individual device's deinit > + * to free the array proper. > */ > -static void array_element_release(Object *obj, const char *name, void *opaque) > +static void release_prop_array(Object *obj, const char *name, void *opaque) > { > - ArrayElementProperty *p = opaque; > - if (p->release) { > - p->release(obj, name, opaque); > + Property *prop = opaque; > + uint32_t *alenptr = object_field_prop_ptr(obj, prop); > + void **arrayptr = (void *)obj + prop->arrayoffset; > + char *elem = *arrayptr; > + int i; > + > + if (!prop->arrayinfo->release) { > + return; > + } > + > + for (i = 0; i < *alenptr; i++) { > + Property elem_prop = array_elem_prop(obj, prop, name, elem); > + prop->arrayinfo->release(obj, NULL, &elem_prop); > + elem += prop->arrayfieldsize; > } > - g_free(p->propname); > - g_free(p); > } > > -static void set_prop_arraylen(Object *obj, Visitor *v, const char *name, > - void *opaque, Error **errp) > +/* > + * Setter for an array property. This sets both the array length (which > + * is technically the property field in the object) and the array itself > + * (a pointer to which is stored in the additional field described by > + * prop->arrayoffset). > + */ > +static void set_prop_array(Object *obj, Visitor *v, const char *name, > + void *opaque, Error **errp) > { > - /* Setter for the property which defines the length of a > - * variable-sized property array. As well as actually setting the > - * array-length field in the device struct, we have to create the > - * array itself and dynamically add the corresponding properties. > - */ > + ERRP_GUARD(); > Property *prop = opaque; > uint32_t *alenptr = object_field_prop_ptr(obj, prop); > void **arrayptr = (void *)obj + prop->arrayoffset; > - void *eltptr; > - const char *arrayname; > - int i; > + GenericList *list, *elem, *next; > + const size_t list_elem_size = sizeof(*list) + prop->arrayfieldsize; > + char *elemptr; > + bool ok = true; > > if (*alenptr) { > error_setg(errp, "array size property %s may not be set more than once", > name); > return; > } > - if (!visit_type_uint32(v, name, alenptr, errp)) { > + > + if (!visit_start_list(v, name, &list, list_elem_size, errp)) { > return; > } > - if (!*alenptr) { > + > + /* Read the whole input into a temporary list */ > + elem = list; > + while (elem) { > + Property elem_prop = array_elem_prop(obj, prop, name, elem->padding); > + prop->arrayinfo->set(obj, v, NULL, &elem_prop, errp); > + if (*errp) { > + ok = false; > + goto out_obj; > + } > + if (*alenptr == INT_MAX) { > + error_setg(errp, "array is too big"); > + return; > + } > + (*alenptr)++; > + elem = visit_next_list(v, elem, list_elem_size); > + } > + > + ok = visit_check_list(v, errp); > +out_obj: > + visit_end_list(v, (void**) &list); > + > + if (!ok) { > + for (elem = list; elem; elem = next) { > + Property elem_prop = array_elem_prop(obj, prop, name, > + elem->padding); > + if (prop->arrayinfo->release) { > + prop->arrayinfo->release(obj, NULL, &elem_prop); > + } > + next = elem->next; > + g_free(elem); > + } > return; > } > > - /* DEFINE_PROP_ARRAY guarantees that name should start with this prefix; > - * strip it off so we can get the name of the array itself. > + /* > + * Now that we know how big the array has to be, move the data over to a > + * linear array and free the temporary list. > */ > - assert(strncmp(name, PROP_ARRAY_LEN_PREFIX, > - strlen(PROP_ARRAY_LEN_PREFIX)) == 0); > - arrayname = name + strlen(PROP_ARRAY_LEN_PREFIX); > + *arrayptr = g_malloc_n(*alenptr, prop->arrayfieldsize); > + elemptr = *arrayptr; > + for (elem = list; elem; elem = next) { > + memcpy(elemptr, elem->padding, prop->arrayfieldsize); > + elemptr += prop->arrayfieldsize; > + next = elem->next; > + g_free(elem); > + } > +} > > - /* Note that it is the responsibility of the individual device's deinit > - * to free the array proper. > - */ > - *arrayptr = eltptr = g_malloc0(*alenptr * prop->arrayfieldsize); > - for (i = 0; i < *alenptr; i++, eltptr += prop->arrayfieldsize) { > - char *propname = g_strdup_printf("%s[%d]", arrayname, i); > - ArrayElementProperty *arrayprop = g_new0(ArrayElementProperty, 1); > - arrayprop->release = prop->arrayinfo->release; > - arrayprop->propname = propname; > - arrayprop->prop.info = prop->arrayinfo; > - arrayprop->prop.name = propname; > - /* This ugly piece of pointer arithmetic sets up the offset so > - * that when the underlying get/set hooks call qdev_get_prop_ptr > - * they get the right answer despite the array element not actually > - * being inside the device struct. > - */ > - arrayprop->prop.offset = eltptr - (void *)obj; > - assert(object_field_prop_ptr(obj, &arrayprop->prop) == eltptr); > - object_property_add(obj, propname, > - arrayprop->prop.info->name, > - field_prop_getter(arrayprop->prop.info), > - field_prop_setter(arrayprop->prop.info), > - array_element_release, > - arrayprop); > +static void get_prop_array(Object *obj, Visitor *v, const char *name, > + void *opaque, Error **errp) > +{ > + ERRP_GUARD(); > + Property *prop = opaque; > + uint32_t *alenptr = object_field_prop_ptr(obj, prop); > + void **arrayptr = (void *)obj + prop->arrayoffset; > + char *elem = *arrayptr; > + GenericList *list; > + const size_t list_elem_size = sizeof(*list) + prop->arrayfieldsize; > + int i; > + bool ok; > + > + if (!visit_start_list(v, name, &list, list_elem_size, errp)) { > + return; > } > + > + for (i = 0; i < *alenptr; i++) { > + Property elem_prop = array_elem_prop(obj, prop, name, elem); > + prop->arrayinfo->get(obj, v, NULL, &elem_prop, errp); > + if (*errp) { > + goto out_obj; > + } > + elem += prop->arrayfieldsize; > + } > + > + /* visit_check_list() can only fail for input visitors */ > + ok = visit_check_list(v, errp); > + assert(ok); > + > +out_obj: > + visit_end_list(v, (void**) &list); > } > > -const PropertyInfo qdev_prop_arraylen = { > - .name = "uint32", > - .get = get_uint32, > - .set = set_prop_arraylen, > - .set_default_value = qdev_propinfo_set_default_value_uint, > +static void default_prop_array(ObjectProperty *op, const Property *prop) > +{ > + object_property_set_default_list(op); > +} > + > +const PropertyInfo qdev_prop_array = { > + .name = "list", > + .get = get_prop_array, > + .set = set_prop_array, > + .release = release_prop_array, > + .set_default_value = default_prop_array, > }; > > /* --- public helpers --- */ > @@ -743,20 +819,8 @@ void qdev_prop_set_enum(DeviceState *dev, const char *name, int value) > > void qdev_prop_set_array(DeviceState *dev, const char *name, QList *values) > { > - const QListEntry *entry; > - g_autofree char *prop_len = g_strdup_printf("len-%s", name); > - unsigned i = 0; > - > - object_property_set_int(OBJECT(dev), prop_len, qlist_size(values), > - &error_abort); > - > - QLIST_FOREACH_ENTRY(values, entry) { > - g_autofree char *prop_idx = g_strdup_printf("%s[%u]", name, i); > - object_property_set_qobject(OBJECT(dev), prop_idx, entry->value, > - &error_abort); > - i++; > - } > - > + object_property_set_qobject(OBJECT(dev), name, QOBJECT(values), > + &error_abort); > qobject_unref(values); > } Appreciate the comments explaining the hairy parts. Reviewed-by: Markus Armbruster <armbru@redhat.com>
On Mon, Oct 30, 2023 at 03:26:58PM +0100, Kevin Wolf wrote: > Until now, array properties are actually implemented with a hack that > uses multiple properties on the QOM level: a static "foo-len" property > and after it is set, dynamically created "foo[i]" properties. > > In external interfaces (-device on the command line and device_add in > QMP), this interface was broken by commit f3558b1b ('qdev: Base object > creation on QDict rather than QemuOpts') because QDicts are unordered > and therefore it could happen that QEMU tried to set the indexed > properties before setting the length, which fails and effectively makes > array properties inaccessible. In particular, this affects the 'ports' > property of the 'rocker' device, which used to be configured like this: > > -device rocker,len-ports=2,ports[0]=dev0,ports[1]=dev1 If you tweak the commit message, you might also want to mention that this form is a shell-glob deathtrap (if you are unlucky enough to have a file named rocker,len-ports=2,ports0=dev0,ports1=dev1 in the current directory), and therefore should have used shell quoting... > > This patch reworks the external interface so that instead of using a > separate top-level property for the length and for each element, we use > a single true array property that accepts a list value. In the external > interfaces, this is naturally expressed as a JSON list and makes array > properties accessible again. The new syntax looks like this: > > -device '{"driver":"rocker","ports":["dev0","dev1"]}' ...at which point, the fact that you HAVE to use shell quoting to get JSON through the command line is less onerous than if the older syntax had been safe without quotes.
diff --git a/include/hw/qdev-properties.h b/include/hw/qdev-properties.h index 7fa2fdb7c9..cac752bade 100644 --- a/include/hw/qdev-properties.h +++ b/include/hw/qdev-properties.h @@ -1,7 +1,10 @@ #ifndef QEMU_QDEV_PROPERTIES_H #define QEMU_QDEV_PROPERTIES_H +#include <stdalign.h> + #include "hw/qdev-core.h" +#include "qapi/visitor.h" /** * Property: @@ -61,7 +64,7 @@ extern const PropertyInfo qdev_prop_size; extern const PropertyInfo qdev_prop_string; extern const PropertyInfo qdev_prop_on_off_auto; extern const PropertyInfo qdev_prop_size32; -extern const PropertyInfo qdev_prop_arraylen; +extern const PropertyInfo qdev_prop_array; extern const PropertyInfo qdev_prop_link; #define DEFINE_PROP(_name, _state, _field, _prop, _type, ...) { \ @@ -115,8 +118,6 @@ extern const PropertyInfo qdev_prop_link; .bitmask = (_bitmask), \ .set_default = false) -#define PROP_ARRAY_LEN_PREFIX "len-" - /** * DEFINE_PROP_ARRAY: * @_name: name of the array @@ -127,28 +128,46 @@ extern const PropertyInfo qdev_prop_link; * @_arrayprop: PropertyInfo defining what property the array elements have * @_arraytype: C type of the array elements * - * Define device properties for a variable-length array _name. A - * static property "len-arrayname" is defined. When the device creator - * sets this property to the desired length of array, further dynamic - * properties "arrayname[0]", "arrayname[1]", ... are defined so the - * device creator can set the array element values. Setting the - * "len-arrayname" property more than once is an error. + * Define device properties for a variable-length array _name. The array is + * represented as a list in the visitor interface. * - * When the array length is set, the @_field member of the device + * @_arraytype is required to be movable with memcpy() and to have an alignment + * such that it can be stored at GenericList.padding. + * + * When the array property is set, the @_field member of the device * struct is set to the array length, and @_arrayfield is set to point - * to (zero-initialised) memory allocated for the array. For a zero - * length array, @_field will be set to 0 and @_arrayfield to NULL. + * to the memory allocated for the array. + * * It is the responsibility of the device deinit code to free the * @_arrayfield memory. */ -#define DEFINE_PROP_ARRAY(_name, _state, _field, \ - _arrayfield, _arrayprop, _arraytype) \ - DEFINE_PROP((PROP_ARRAY_LEN_PREFIX _name), \ - _state, _field, qdev_prop_arraylen, uint32_t, \ - .set_default = true, \ - .defval.u = 0, \ - .arrayinfo = &(_arrayprop), \ - .arrayfieldsize = sizeof(_arraytype), \ +#define DEFINE_PROP_ARRAY(_name, _state, _field, \ + _arrayfield, _arrayprop, _arraytype) \ + DEFINE_PROP(_name, _state, _field, qdev_prop_array, uint32_t, \ + .set_default = true, \ + .defval.u = 0, \ + .arrayinfo = &(_arrayprop), \ + /* \ + * set_prop_array() temporarily stores elements at \ + * GenericList.padding. Make sure that this has the \ + * right alignment for @_arraytype. \ + * \ + * Hack: In this place, neither static assertions work \ + * nor is a statement expression allowed. This \ + * abomination of an expression works because inside \ + * the declaration of a dummy struct, static assertions \ + * are possible. Using the comma operator causes \ + * warnings about an unused value and casting to void \ + * makes the expression not constant in gcc, so instead \ + * of ignoring the first part, make it evaluate to 0 \ + * and add it to the actual result. \ + */ \ + .arrayfieldsize = (!sizeof(struct { \ + QEMU_BUILD_BUG_ON( \ + !QEMU_IS_ALIGNED(sizeof(GenericList), \ + alignof(_arraytype))); \ + int dummy; \ + }) + sizeof(_arraytype)), \ .arrayoffset = offsetof(_state, _arrayfield)) #define DEFINE_PROP_LINK(_name, _state, _field, _type, _ptr_type) \ diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c index fb4daba799..4f3e1152be 100644 --- a/hw/core/qdev-properties.c +++ b/hw/core/qdev-properties.c @@ -546,98 +546,174 @@ const PropertyInfo qdev_prop_size32 = { /* --- support for array properties --- */ -/* Used as an opaque for the object properties we add for each - * array element. Note that the struct Property must be first - * in the struct so that a pointer to this works as the opaque - * for the underlying element's property hooks as well as for - * our own release callback. +/* + * Given an array property @parent_prop in @obj, return a Property for a + * specific element of the array. Arrays are backed by an uint32_t length field + * and an element array. @elem points at an element in this element array. */ -typedef struct { - struct Property prop; - char *propname; - ObjectPropertyRelease *release; -} ArrayElementProperty; - -/* object property release callback for array element properties: - * we call the underlying element's property release hook, and - * then free the memory we allocated when we added the property. +static Property array_elem_prop(Object *obj, Property *parent_prop, + const char *name, char *elem) +{ + return (Property) { + .info = parent_prop->arrayinfo, + .name = name, + /* + * This ugly piece of pointer arithmetic sets up the offset so + * that when the underlying release hook calls qdev_get_prop_ptr + * they get the right answer despite the array element not actually + * being inside the device struct. + */ + .offset = (uintptr_t)elem - (uintptr_t)obj, + }; +} + +/* + * Object property release callback for array properties: We call the + * underlying element's property release hook for each element. + * + * Note that it is the responsibility of the individual device's deinit + * to free the array proper. */ -static void array_element_release(Object *obj, const char *name, void *opaque) +static void release_prop_array(Object *obj, const char *name, void *opaque) { - ArrayElementProperty *p = opaque; - if (p->release) { - p->release(obj, name, opaque); + Property *prop = opaque; + uint32_t *alenptr = object_field_prop_ptr(obj, prop); + void **arrayptr = (void *)obj + prop->arrayoffset; + char *elem = *arrayptr; + int i; + + if (!prop->arrayinfo->release) { + return; + } + + for (i = 0; i < *alenptr; i++) { + Property elem_prop = array_elem_prop(obj, prop, name, elem); + prop->arrayinfo->release(obj, NULL, &elem_prop); + elem += prop->arrayfieldsize; } - g_free(p->propname); - g_free(p); } -static void set_prop_arraylen(Object *obj, Visitor *v, const char *name, - void *opaque, Error **errp) +/* + * Setter for an array property. This sets both the array length (which + * is technically the property field in the object) and the array itself + * (a pointer to which is stored in the additional field described by + * prop->arrayoffset). + */ +static void set_prop_array(Object *obj, Visitor *v, const char *name, + void *opaque, Error **errp) { - /* Setter for the property which defines the length of a - * variable-sized property array. As well as actually setting the - * array-length field in the device struct, we have to create the - * array itself and dynamically add the corresponding properties. - */ + ERRP_GUARD(); Property *prop = opaque; uint32_t *alenptr = object_field_prop_ptr(obj, prop); void **arrayptr = (void *)obj + prop->arrayoffset; - void *eltptr; - const char *arrayname; - int i; + GenericList *list, *elem, *next; + const size_t list_elem_size = sizeof(*list) + prop->arrayfieldsize; + char *elemptr; + bool ok = true; if (*alenptr) { error_setg(errp, "array size property %s may not be set more than once", name); return; } - if (!visit_type_uint32(v, name, alenptr, errp)) { + + if (!visit_start_list(v, name, &list, list_elem_size, errp)) { return; } - if (!*alenptr) { + + /* Read the whole input into a temporary list */ + elem = list; + while (elem) { + Property elem_prop = array_elem_prop(obj, prop, name, elem->padding); + prop->arrayinfo->set(obj, v, NULL, &elem_prop, errp); + if (*errp) { + ok = false; + goto out_obj; + } + if (*alenptr == INT_MAX) { + error_setg(errp, "array is too big"); + return; + } + (*alenptr)++; + elem = visit_next_list(v, elem, list_elem_size); + } + + ok = visit_check_list(v, errp); +out_obj: + visit_end_list(v, (void**) &list); + + if (!ok) { + for (elem = list; elem; elem = next) { + Property elem_prop = array_elem_prop(obj, prop, name, + elem->padding); + if (prop->arrayinfo->release) { + prop->arrayinfo->release(obj, NULL, &elem_prop); + } + next = elem->next; + g_free(elem); + } return; } - /* DEFINE_PROP_ARRAY guarantees that name should start with this prefix; - * strip it off so we can get the name of the array itself. + /* + * Now that we know how big the array has to be, move the data over to a + * linear array and free the temporary list. */ - assert(strncmp(name, PROP_ARRAY_LEN_PREFIX, - strlen(PROP_ARRAY_LEN_PREFIX)) == 0); - arrayname = name + strlen(PROP_ARRAY_LEN_PREFIX); + *arrayptr = g_malloc_n(*alenptr, prop->arrayfieldsize); + elemptr = *arrayptr; + for (elem = list; elem; elem = next) { + memcpy(elemptr, elem->padding, prop->arrayfieldsize); + elemptr += prop->arrayfieldsize; + next = elem->next; + g_free(elem); + } +} - /* Note that it is the responsibility of the individual device's deinit - * to free the array proper. - */ - *arrayptr = eltptr = g_malloc0(*alenptr * prop->arrayfieldsize); - for (i = 0; i < *alenptr; i++, eltptr += prop->arrayfieldsize) { - char *propname = g_strdup_printf("%s[%d]", arrayname, i); - ArrayElementProperty *arrayprop = g_new0(ArrayElementProperty, 1); - arrayprop->release = prop->arrayinfo->release; - arrayprop->propname = propname; - arrayprop->prop.info = prop->arrayinfo; - arrayprop->prop.name = propname; - /* This ugly piece of pointer arithmetic sets up the offset so - * that when the underlying get/set hooks call qdev_get_prop_ptr - * they get the right answer despite the array element not actually - * being inside the device struct. - */ - arrayprop->prop.offset = eltptr - (void *)obj; - assert(object_field_prop_ptr(obj, &arrayprop->prop) == eltptr); - object_property_add(obj, propname, - arrayprop->prop.info->name, - field_prop_getter(arrayprop->prop.info), - field_prop_setter(arrayprop->prop.info), - array_element_release, - arrayprop); +static void get_prop_array(Object *obj, Visitor *v, const char *name, + void *opaque, Error **errp) +{ + ERRP_GUARD(); + Property *prop = opaque; + uint32_t *alenptr = object_field_prop_ptr(obj, prop); + void **arrayptr = (void *)obj + prop->arrayoffset; + char *elem = *arrayptr; + GenericList *list; + const size_t list_elem_size = sizeof(*list) + prop->arrayfieldsize; + int i; + bool ok; + + if (!visit_start_list(v, name, &list, list_elem_size, errp)) { + return; } + + for (i = 0; i < *alenptr; i++) { + Property elem_prop = array_elem_prop(obj, prop, name, elem); + prop->arrayinfo->get(obj, v, NULL, &elem_prop, errp); + if (*errp) { + goto out_obj; + } + elem += prop->arrayfieldsize; + } + + /* visit_check_list() can only fail for input visitors */ + ok = visit_check_list(v, errp); + assert(ok); + +out_obj: + visit_end_list(v, (void**) &list); } -const PropertyInfo qdev_prop_arraylen = { - .name = "uint32", - .get = get_uint32, - .set = set_prop_arraylen, - .set_default_value = qdev_propinfo_set_default_value_uint, +static void default_prop_array(ObjectProperty *op, const Property *prop) +{ + object_property_set_default_list(op); +} + +const PropertyInfo qdev_prop_array = { + .name = "list", + .get = get_prop_array, + .set = set_prop_array, + .release = release_prop_array, + .set_default_value = default_prop_array, }; /* --- public helpers --- */ @@ -743,20 +819,8 @@ void qdev_prop_set_enum(DeviceState *dev, const char *name, int value) void qdev_prop_set_array(DeviceState *dev, const char *name, QList *values) { - const QListEntry *entry; - g_autofree char *prop_len = g_strdup_printf("len-%s", name); - unsigned i = 0; - - object_property_set_int(OBJECT(dev), prop_len, qlist_size(values), - &error_abort); - - QLIST_FOREACH_ENTRY(values, entry) { - g_autofree char *prop_idx = g_strdup_printf("%s[%u]", name, i); - object_property_set_qobject(OBJECT(dev), prop_idx, entry->value, - &error_abort); - i++; - } - + object_property_set_qobject(OBJECT(dev), name, QOBJECT(values), + &error_abort); qobject_unref(values); }
Until now, array properties are actually implemented with a hack that uses multiple properties on the QOM level: a static "foo-len" property and after it is set, dynamically created "foo[i]" properties. In external interfaces (-device on the command line and device_add in QMP), this interface was broken by commit f3558b1b ('qdev: Base object creation on QDict rather than QemuOpts') because QDicts are unordered and therefore it could happen that QEMU tried to set the indexed properties before setting the length, which fails and effectively makes array properties inaccessible. In particular, this affects the 'ports' property of the 'rocker' device, which used to be configured like this: -device rocker,len-ports=2,ports[0]=dev0,ports[1]=dev1 This patch reworks the external interface so that instead of using a separate top-level property for the length and for each element, we use a single true array property that accepts a list value. In the external interfaces, this is naturally expressed as a JSON list and makes array properties accessible again. The new syntax looks like this: -device '{"driver":"rocker","ports":["dev0","dev1"]}' Creating an array property on the command line without using JSON format is currently not possible. This could be fixed by switching from QemuOpts to a keyval parser, which however requires consideration of the compatibility implications. All internal users of devices with array properties go through qdev_prop_set_array() at this point, so updating it takes care of all of them. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1090 Fixes: f3558b1b763683bb877f7dd5b282469cdadc65c3 Signed-off-by: Kevin Wolf <kwolf@redhat.com> --- include/hw/qdev-properties.h | 59 +++++---- hw/core/qdev-properties.c | 224 ++++++++++++++++++++++------------- 2 files changed, 183 insertions(+), 100 deletions(-)