linux-kernel - Re: [PATCH 3/6] KVM: selftests: Create a new guest

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Message-ID: <CA+EHjTyN_YTkn5k5eqY1gdbQ+SQX_0C1cDRzEhvLoRQRYcp7RQ@mail.gmail.com>
Date: Mon, 29 Sep 2025 10:24:14 +0100
From: Fuad Tabba <tabba@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, David Hildenbrand <david@...hat.com>, 
	Ackerley Tng <ackerleytng@...gle.com>
Subject: Re: [PATCH 3/6] KVM: selftests: Create a new guest_memfd for each testcase

Hi Sean,

On Fri, 26 Sept 2025 at 17:31, Sean Christopherson <seanjc@...gle.com> wrote:
>
> Refactor the guest_memfd selftest to improve test isolation by creating a
> a new guest_memfd for each testcase.  Currently, the test reuses a single
> guest_memfd instance for all testcases, and thus creates dependencies
> between tests, e.g. not truncating folios from the guest_memfd instance
> at the end of a test could lead to unexpected results (see the PUNCH_HOLE
> purging that needs to done by in-flight the NUMA testcases[1]).
>
> Invoke each test via a macro wrapper to create and close a guest_memfd
> to cut down on the boilerplate copy+paste needed to create a test.
>
> Link: https://lore.kernel.org/all/20250827175247.83322-10-shivankg@amd.com
> Reported-by: Ackerley Tng <ackerleytng@...gle.com>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  .../testing/selftests/kvm/guest_memfd_test.c  | 31 ++++++++++---------
>  1 file changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
> index 8251d019206a..60c6dec63490 100644
> --- a/tools/testing/selftests/kvm/guest_memfd_test.c
> +++ b/tools/testing/selftests/kvm/guest_memfd_test.c
> @@ -26,7 +26,7 @@
>
>  static size_t page_size;
>
> -static void test_file_read_write(int fd)
> +static void test_file_read_write(int fd, size_t total_size)
>  {
>         char buf[64];
>
> @@ -259,14 +259,18 @@ static void test_guest_memfd_flags(struct kvm_vm *vm, uint64_t valid_flags)
>         }
>  }
>
> +#define gmem_test(__test, __vm, __flags)                               \
> +do {                                                                   \
> +       int fd = vm_create_guest_memfd(__vm, page_size * 4, __flags);   \
> +                                                                       \
> +       test_##__test(fd, page_size * 4);                               \
> +       close(fd);                                                      \
> +} while (0)
> +

Can we have a const for total_size that sets it to `page_size * 4`
instead of hardcoding that value twice?

With that:

Reviewed-by: Fuad Tabba <tabba@...gle.com>
Tested-by: Fuad Tabba <tabba@...gle.com>

Cheers,
/fuad






>  static void test_guest_memfd(unsigned long vm_type)
>  {
>         uint64_t flags = 0;
>         struct kvm_vm *vm;
> -       size_t total_size;
> -       int fd;
> -
> -       total_size = page_size * 4;
>
>         vm = vm_create_barebones_type(vm_type);
>
> @@ -276,24 +280,21 @@ static void test_guest_memfd(unsigned long vm_type)
>         test_create_guest_memfd_multiple(vm);
>         test_create_guest_memfd_invalid_sizes(vm, flags);
>
> -       fd = vm_create_guest_memfd(vm, total_size, flags);
> -
> -       test_file_read_write(fd);
> +       gmem_test(file_read_write, vm, flags);
>
>         if (flags & GUEST_MEMFD_FLAG_MMAP) {
> -               test_mmap_supported(fd, total_size);
> -               test_fault_overflow(fd, total_size);
> +               gmem_test(mmap_supported, vm, flags);
> +               gmem_test(fault_overflow, vm, flags);
>         } else {
> -               test_mmap_not_supported(fd, total_size);
> +               gmem_test(mmap_not_supported, vm, flags);
>         }
>
> -       test_file_size(fd, total_size);
> -       test_fallocate(fd, total_size);
> -       test_invalid_punch_hole(fd, total_size);
> +       gmem_test(file_size, vm, flags);
> +       gmem_test(fallocate, vm, flags);
> +       gmem_test(invalid_punch_hole, vm, flags);
>
>         test_guest_memfd_flags(vm, flags);
>
> -       close(fd);
>         kvm_vm_free(vm);
>  }
>
> --
> 2.51.0.536.g15c5d4f767-goog
>