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

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Date:   Wed, 8 Apr 2020 23:45:39 -0300
From:   Wainer dos Santos Moschetta <wainersm@...hat.com>
To:     Krish Sadhukhan <krish.sadhukhan@...cle.com>, pbonzini@...hat.com,
        kvm@...r.kernel.org
Cc:     drjones@...hat.com, david@...hat.com, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v4 1/2] selftests: kvm: Add vm_get_fd() in kvm_util


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@...hat.com>
>> Signed-off-by: Wainer dos Santos Moschetta <wainersm@...hat.com>
>> ---
>>   tools/testing/selftests/kvm/include/kvm_util.h | 1 +
>>   tools/testing/selftests/kvm/lib/kvm_util.c     | 5 +++++
>>   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);
>>   unsigned int vm_get_page_size(struct kvm_vm *vm);
>>   unsigned int vm_get_page_shift(struct kvm_vm *vm);
>>   unsigned int vm_get_max_gfn(struct kvm_vm *vm);
>> +int vm_get_fd(struct kvm_vm *vm);
>>     unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, 
>> size_t size);
>>   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)
>>       return vm->max_gfn;
>>   }
>>   +int vm_get_fd(struct kvm_vm *vm)
>> +{
>> +        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 ‘test_add_max_slots’:
mem_slot_test.c:62:16: error: dereferencing pointer to incomplete type 
‘struct kvm_vm’
   ret = ioctl(vm->fd, KVM_SET_USER_MEMORY_REGION,
                 ^~

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