| Message ID | 20231021134015.1119597-1-daan.j.demeyer@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add class property to configure KVM device node to use | expand |
On Sat, Oct 21, 2023 at 03:40:15PM +0200, Daan De Meyer wrote: > This allows passing the KVM device node to use as a file > descriptor via /dev/fdset/XX. Passing the device node to > use as a file descriptor allows running qemu unprivileged > even when the user running qemu is not in the kvm group > on distributions where access to /dev/kvm is gated behind > membership of the kvm group (as long as the process invoking > qemu is able to open /dev/kvm and passes the file descriptor > to qemu). > > Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com> > --- > accel/kvm/kvm-all.c | 25 ++++++++++++++++++++++++- > include/sysemu/kvm_int.h | 1 + > qemu-options.hx | 8 +++++++- > 3 files changed, 32 insertions(+), 2 deletions(-) Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> With regards, Daniel
Anything else needed before this patch can be merged? Cheers, Daan On Wed, 25 Oct 2023 at 19:37, Daniel P. Berrangé <berrange@redhat.com> wrote: > > On Sat, Oct 21, 2023 at 03:40:15PM +0200, Daan De Meyer wrote: > > This allows passing the KVM device node to use as a file > > descriptor via /dev/fdset/XX. Passing the device node to > > use as a file descriptor allows running qemu unprivileged > > even when the user running qemu is not in the kvm group > > on distributions where access to /dev/kvm is gated behind > > membership of the kvm group (as long as the process invoking > > qemu is able to open /dev/kvm and passes the file descriptor > > to qemu). > > > > Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com> > > --- > > accel/kvm/kvm-all.c | 25 ++++++++++++++++++++++++- > > include/sysemu/kvm_int.h | 1 + > > qemu-options.hx | 8 +++++++- > > 3 files changed, 32 insertions(+), 2 deletions(-) > > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> > > > With regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| >
Ping Daan On Sat, 28 Oct 2023 at 14:07, Daan De Meyer <daan.j.demeyer@gmail.com> wrote: > > Anything else needed before this patch can be merged? > > Cheers, > > Daan > > On Wed, 25 Oct 2023 at 19:37, Daniel P. Berrangé <berrange@redhat.com> wrote: > > > > On Sat, Oct 21, 2023 at 03:40:15PM +0200, Daan De Meyer wrote: > > > This allows passing the KVM device node to use as a file > > > descriptor via /dev/fdset/XX. Passing the device node to > > > use as a file descriptor allows running qemu unprivileged > > > even when the user running qemu is not in the kvm group > > > on distributions where access to /dev/kvm is gated behind > > > membership of the kvm group (as long as the process invoking > > > qemu is able to open /dev/kvm and passes the file descriptor > > > to qemu). > > > > > > Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com> > > > --- > > > accel/kvm/kvm-all.c | 25 ++++++++++++++++++++++++- > > > include/sysemu/kvm_int.h | 1 + > > > qemu-options.hx | 8 +++++++- > > > 3 files changed, 32 insertions(+), 2 deletions(-) > > > > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> > > > > > > With regards, > > Daniel > > -- > > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > > |: https://libvirt.org -o- https://fstop138.berrange.com :| > > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| > >
Queued, thanks. Paolo
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 72e1d1141c..3e0b2d00e9 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -2478,7 +2478,7 @@ static int kvm_init(MachineState *ms) QTAILQ_INIT(&s->kvm_sw_breakpoints); #endif QLIST_INIT(&s->kvm_parked_vcpus); - s->fd = qemu_open_old("/dev/kvm", O_RDWR); + s->fd = qemu_open_old(s->device ?: "/dev/kvm", O_RDWR); if (s->fd == -1) { fprintf(stderr, "Could not access KVM kernel module: %m\n"); ret = -errno; @@ -3775,6 +3775,24 @@ static void kvm_set_dirty_ring_size(Object *obj, Visitor *v, s->kvm_dirty_ring_size = value; } +static char *kvm_get_device(Object *obj, + Error **errp G_GNUC_UNUSED) +{ + KVMState *s = KVM_STATE(obj); + + return g_strdup(s->device); +} + +static void kvm_set_device(Object *obj, + const char *value, + Error **errp G_GNUC_UNUSED) +{ + KVMState *s = KVM_STATE(obj); + + g_free(s->device); + s->device = g_strdup(value); +} + static void kvm_accel_instance_init(Object *obj) { KVMState *s = KVM_STATE(obj); @@ -3793,6 +3811,7 @@ static void kvm_accel_instance_init(Object *obj) s->xen_version = 0; s->xen_gnttab_max_frames = 64; s->xen_evtchn_max_pirq = 256; + s->device = NULL; } /** @@ -3833,6 +3852,10 @@ static void kvm_accel_class_init(ObjectClass *oc, void *data) object_class_property_set_description(oc, "dirty-ring-size", "Size of KVM dirty page ring buffer (default: 0, i.e. use bitmap)"); + object_class_property_add_str(oc, "device", kvm_get_device, kvm_set_device); + object_class_property_set_description(oc, "device", + "Path to the device node to use (default: /dev/kvm)"); + kvm_arch_accel_class_init(oc); } diff --git a/include/sysemu/kvm_int.h b/include/sysemu/kvm_int.h index a5b9122cb8..19a5364a4b 100644 --- a/include/sysemu/kvm_int.h +++ b/include/sysemu/kvm_int.h @@ -124,6 +124,7 @@ struct KVMState uint32_t xen_caps; uint16_t xen_gnttab_max_frames; uint16_t xen_evtchn_max_pirq; + char *device; }; void kvm_memory_listener_register(KVMState *s, KVMMemoryListener *kml, diff --git a/qemu-options.hx b/qemu-options.hx index 54a7e94970..40ad15a9da 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -188,7 +188,8 @@ DEF("accel", HAS_ARG, QEMU_OPTION_accel, " dirty-ring-size=n (KVM dirty ring GFN count, default 0)\n" " eager-split-size=n (KVM Eager Page Split chunk size, default 0, disabled. ARM only)\n" " notify-vmexit=run|internal-error|disable,notify-window=n (enable notify VM exit and set notify window, x86 only)\n" - " thread=single|multi (enable multi-threaded TCG)\n", QEMU_ARCH_ALL) + " thread=single|multi (enable multi-threaded TCG)\n" + " device=path (KVM device path, default /dev/kvm)\n", QEMU_ARCH_ALL) SRST ``-accel name[,prop=value[,...]]`` This is used to enable an accelerator. Depending on the target @@ -269,6 +270,11 @@ SRST open up for a specified of time (i.e. notify-window). Default: notify-vmexit=run,notify-window=0. + ``device=path`` + Sets the path to the KVM device node. Defaults to ``/dev/kvm``. This + option can be used to pass the KVM device to use via a file descriptor + by setting the value to ``/dev/fdset/NN``. + ERST DEF("smp", HAS_ARG, QEMU_OPTION_smp,
This allows passing the KVM device node to use as a file descriptor via /dev/fdset/XX. Passing the device node to use as a file descriptor allows running qemu unprivileged even when the user running qemu is not in the kvm group on distributions where access to /dev/kvm is gated behind membership of the kvm group (as long as the process invoking qemu is able to open /dev/kvm and passes the file descriptor to qemu). Signed-off-by: Daan De Meyer <daan.j.demeyer@gmail.com> --- accel/kvm/kvm-all.c | 25 ++++++++++++++++++++++++- include/sysemu/kvm_int.h | 1 + qemu-options.hx | 8 +++++++- 3 files changed, 32 insertions(+), 2 deletions(-)