Re: [PATCH RFC 07/17] KVM: selftests: Test rejection of unsupported filesystem for resource_fd

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] kvm: selftests: missing capability check for GUEST_MEMFD_FLAG_USE_RESOURCE
--

commit 12edbf910d6d9507b605565dea5dca809a2eece9
Author: Ackerley Tng <ackerleytng@google.com>

KVM: selftests: Test rejection of unsupported filesystem for resource_fd

This commit adds test coverage to verify that passing a directory file
descriptor from an unsupported filesystem fails with EOPNOTSUPP.

> diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
> index 84b958b9ef715..31bc74c4c26bd 100644
> --- a/tools/testing/selftests/kvm/guest_memfd_test.c
> +++ b/tools/testing/selftests/kvm/guest_memfd_test.c
[ ... ]
> @@ -495,6 +516,7 @@ static void test_guest_memfd(unsigned long vm_type)
>  	test_guest_memfd_flags(vm);
>  
>  	test_resource_fd_invalid(vm);
> +	test_resource_fd_unsupported_fs(vm);

[Severity: Medium]
Does this new test invocation need to verify if the underlying KVM module
supports the GUEST_MEMFD_FLAG_USE_RESOURCE capability before running?

The test_guest_memfd() function unconditionally calls
test_resource_fd_unsupported_fs(), which passes the
GUEST_MEMFD_FLAG_USE_RESOURCE flag to KVM. On older kernels lacking this
feature, the ioctl will reject the unknown flag with -EINVAL.

Since the test explicitly expects -EOPNOTSUPP, this mismatch will cause the
assertion to fail and abort the test run, unexpectedly breaking backward
compatibility for the test suite.

>  
>  	__test_guest_memfd(vm, 0);

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260925-gmem-tmpfs-backend-v1-0-d36159822d18@google.com?part=7