Re: [PATCH v4 1/2] selftests: kvm: Add vm_get_fd() in kvm_util

[Wainer dos Santos Moschetta]

On 4/8/20 10:25 PM, Krish Sadhukhan wrote:
> On 4/8/20 3:08 PM, Wainer dos Santos Moschetta wrote:
> > Introduces the vm_get_fd() function in kvm_util which returns
> > the VM file descriptor.
> >
> > Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
> > Signed-off-by: Wainer dos Santos Moschetta <wainersm@xxxxxxxxxx>
> > ---
> > Â tools/testing/selftests/kvm/include/kvm_util.h | 1 +
> > Â tools/testing/selftests/kvm/lib/kvm_util.cÂÂÂÂ | 5 +++++
> > Â 2 files changed, 6 insertions(+)
> >
> > diff --git a/tools/testing/selftests/kvm/include/kvm_util.h 
> > b/tools/testing/selftests/kvm/include/kvm_util.h
> > index a99b875f50d2..4e122819ee24 100644
> > --- a/tools/testing/selftests/kvm/include/kvm_util.h
> > +++ b/tools/testing/selftests/kvm/include/kvm_util.h
> > @@ -254,6 +254,7 @@ bool vm_is_unrestricted_guest(struct kvm_vm *vm);
> > Â unsigned int vm_get_page_size(struct kvm_vm *vm);
> > Â unsigned int vm_get_page_shift(struct kvm_vm *vm);
> > Â unsigned int vm_get_max_gfn(struct kvm_vm *vm);
> > +int vm_get_fd(struct kvm_vm *vm);
> > Â Â unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, 
> > size_t size);
> > Â unsigned int vm_num_host_pages(enum vm_guest_mode mode, unsigned 
> > int num_guest_pages);
> > diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c 
> > b/tools/testing/selftests/kvm/lib/kvm_util.c
> > index 8a3523d4434f..3e36a1eb8771 100644
> > --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> > +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> > @@ -1734,6 +1734,11 @@ unsigned int vm_get_max_gfn(struct kvm_vm *vm)
> > ÂÂÂÂÂ return vm->max_gfn;
> > Â }
> > Â +int vm_get_fd(struct kvm_vm *vm)
> > +{
> > +ÂÂÂÂÂÂÂ return vm->fd;
> > +}
> > +
>
>
> I am just trying to understand why we need a separate function when 
> the 'vm' variable is all local within the same file. There are a 
> number of places in kvm_util.c where it is used directly.


The problem is to access of kvm_vm attributes outside of kvm_utils.c. 
For example, if I try to vm->fd in my test I get the compiler error:

mem_slot_test.c: In function âtest_add_max_slotsâ:
mem_slot_test.c:62:16: error: dereferencing pointer to incomplete type 
âstruct kvm_vmâ
 ret = ioctl(vm->fd, KVM_SET_USER_MEMORY_REGION,
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ ^~

> > Â static unsigned int vm_calc_num_pages(unsigned int num_pages,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ unsigned int page_shift,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ unsigned int new_page_shift,