| Message ID | 1458711153-15988-4-git-send-email-peterx@redhat.com |
|---|---|
| State | New |
| Headers | show |
On 23/03/16 08:32, Peter Xu wrote: > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h > index 6695fa7..8738fa1 100644 > --- a/include/sysemu/kvm.h > +++ b/include/sysemu/kvm.h > @@ -306,6 +306,15 @@ void kvm_device_access(int fd, int group, uint64_t attr, > */ > int kvm_create_device(KVMState *s, uint64_t type, bool test); > > +/** > + * kvm_support_device - probe whether KVM support specific device > + * > + * @vmfd: The fd handler for VM > + * @type: type of device > + * > + * @return: true if supported, otherwise false. > + */ > +bool kvm_support_device(int vmfd, uint64_t type); Why don't name the function like 'kvm_device_supported' to better express its predicative nature? Kind regards, Sergey
On Wed, Mar 23, 2016 at 03:28:28PM +0300, Sergey Fedorov wrote: > On 23/03/16 08:32, Peter Xu wrote: > > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h > > index 6695fa7..8738fa1 100644 > > --- a/include/sysemu/kvm.h > > +++ b/include/sysemu/kvm.h > > @@ -306,6 +306,15 @@ void kvm_device_access(int fd, int group, uint64_t attr, > > */ > > int kvm_create_device(KVMState *s, uint64_t type, bool test); > > > > +/** > > + * kvm_support_device - probe whether KVM support specific device > > + * > > + * @vmfd: The fd handler for VM > > + * @type: type of device > > + * > > + * @return: true if supported, otherwise false. > > + */ > > +bool kvm_support_device(int vmfd, uint64_t type); > > Why don't name the function like 'kvm_device_supported' to better express its predicative nature? Because I am trying to follow existing naming style, like: "kvm_create_device" (please see above). Thanks. -- peterx
On 23/03/16 17:56, Peter Xu wrote: > On Wed, Mar 23, 2016 at 03:28:28PM +0300, Sergey Fedorov wrote: >> On 23/03/16 08:32, Peter Xu wrote: >>> diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h >>> index 6695fa7..8738fa1 100644 >>> --- a/include/sysemu/kvm.h >>> +++ b/include/sysemu/kvm.h >>> @@ -306,6 +306,15 @@ void kvm_device_access(int fd, int group, uint64_t attr, >>> */ >>> int kvm_create_device(KVMState *s, uint64_t type, bool test); >>> >>> +/** >>> + * kvm_support_device - probe whether KVM support specific device >>> + * >>> + * @vmfd: The fd handler for VM >>> + * @type: type of device >>> + * >>> + * @return: true if supported, otherwise false. >>> + */ >>> +bool kvm_support_device(int vmfd, uint64_t type); >> Why don't name the function like 'kvm_device_supported' to better express its predicative nature? > Because I am trying to follow existing naming style, like: > "kvm_create_device" (please see above). Yes, but kvm_create_device() returns a file descriptor whereas this function is predicative. Personally, I like the convention described in chapter 16 of Linux kernel coding style [1]: If the name of a function is an action or an imperative command, the function should return an error-code integer. If the name is a predicate, the function should return a "succeeded" boolean. [1] https://www.kernel.org/doc/Documentation/CodingStyle Kind regards, Sergey
On Wed, Mar 23, 2016 at 06:03:32PM +0300, Sergey Fedorov wrote: > Yes, but kvm_create_device() returns a file descriptor whereas this > function is predicative. Personally, I like the convention described in > chapter 16 of Linux kernel coding style [1]: > > If the name of a function is an action or an imperative command, > the function should return an error-code integer. If the name > is a predicate, the function should return a "succeeded" boolean. The above is talking about return values. Maybe you were trying to reference this one as example about add_work() and pci_dev_present(): For example, "add work" is a command, and the add_work() function returns 0 for success or -EBUSY for failure. In the same way, "PCI device present" is a predicate, and the pci_dev_present() function returns 1 if it succeeds in finding a matching device or 0 if it doesn't. Seems make sense. Will take your advice. Thanks. -- peterx
diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h index 6695fa7..8738fa1 100644 --- a/include/sysemu/kvm.h +++ b/include/sysemu/kvm.h @@ -306,6 +306,15 @@ void kvm_device_access(int fd, int group, uint64_t attr, */ int kvm_create_device(KVMState *s, uint64_t type, bool test); +/** + * kvm_support_device - probe whether KVM support specific device + * + * @vmfd: The fd handler for VM + * @type: type of device + * + * @return: true if supported, otherwise false. + */ +bool kvm_support_device(int vmfd, uint64_t type); /* Arch specific hooks */ diff --git a/kvm-all.c b/kvm-all.c index 44c0464..77deccc 100644 --- a/kvm-all.c +++ b/kvm-all.c @@ -2339,6 +2339,21 @@ int kvm_create_device(KVMState *s, uint64_t type, bool test) return test ? 0 : create_dev.fd; } +bool kvm_support_device(int vmfd, uint64_t type) +{ + struct kvm_create_device create_dev = { + .type = type, + .fd = -1, + .flags = KVM_CREATE_DEVICE_TEST, + }; + + if (ioctl(vmfd, KVM_CHECK_EXTENSION, KVM_CAP_DEVICE_CTRL) <= 0) { + return false; + } + + return (ioctl(vmfd, KVM_CREATE_DEVICE, &create_dev) >= 0); +} + int kvm_set_one_reg(CPUState *cs, uint64_t id, void *source) { struct kvm_one_reg reg;
This can be used when probing whether KVM support specific device. Here, a raw vmfd is used. Signed-off-by: Peter Xu <peterx@redhat.com> --- include/sysemu/kvm.h | 9 +++++++++ kvm-all.c | 15 +++++++++++++++ 2 files changed, 24 insertions(+)