Re: [PATCH v5 5/5] KVM: selftests: Add nested pre-fault test for arm64

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The `KVM_PRE_FAULT_MEMORY` ioctl loop in `pre_fault()` fails to handle partial success, causing spurious test failures if the ioctl yields or is interrupted.
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commit ee1e827d8efbd103bf9ab1322ee50ba8c3895869
Author: Jack Thomson <jackabt@amazon.com>

KVM: selftests: Add nested pre-fault test for arm64

This commit adds an arm64 nested-virt selftest for KVM_PRE_FAULT_MEMORY to
verify that prefaulting correctly targets the canonical stage-2 when the
guest's last-run context has a nested/shadow stage-2 MMU.

> diff --git a/tools/testing/selftests/kvm/arm64/nv_pre_fault_memory_test.c b/tools/testing/selftests/kvm/arm64/nv_pre_fault_memory_test.c
> new file mode 100644
> index 0000000000000..2bbd5540599c0
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/arm64/nv_pre_fault_memory_test.c

[ ... ]

> +static void pre_fault(struct kvm_vcpu *vcpu, u64 gpa, u64 size)
> +{
> +	struct kvm_pre_fault_memory range = {
> +		.gpa = gpa,
> +		.size = size,
> +	};
> +	int ret;
> +
> +	do {
> +		ret = __vcpu_ioctl(vcpu, KVM_PRE_FAULT_MEMORY, &range);
> +	} while (ret < 0 && errno == EINTR);

[Severity: Medium]
Does this loop handle partial successes correctly? If the ioctl is interrupted
by a signal or yields after successfully mapping at least one page, it returns
0 and updates range.size with the remaining bytes to process.

If that happens, this loop will exit immediately and the test will spuriously
fail the TEST_ASSERT_EQ(range.size, 0) assertion below. Should this loop
continue as long as ret == 0 and range.size > 0?

> +
> +	TEST_ASSERT(!ret, "KVM_PRE_FAULT_MEMORY failed, ret: %d errno: %d",
> +		    ret, errno);
> +	TEST_ASSERT_EQ(range.size, 0);
> +}

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Sashiko AI review · https://sashiko.dev/#/patchset/20260612162354.73378-1-jackabt.amazon@gmail.com?part=5