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

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Message-ID: <aed511d0-a51e-bc4c-a265-d9ede82e18f2@oracle.com>
Date:   Thu, 9 Apr 2020 10:57:19 -0700
From:   Krish Sadhukhan <krish.sadhukhan@...cle.com>
To:     Wainer dos Santos Moschetta <wainersm@...hat.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 7:45 PM, Wainer dos Santos Moschetta wrote:
>
> 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,
>                 ^~


My bad !  I missed the fact that the structure is defined in 
kvm_util_internal.h and not in kvm_util.h.


Reviewed-by: Krish Sadhukhan <krish.sadhukhan@...cle.com>

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