Re: [PATCH v3 04/12] KVM: Rename .gmem_invalidate() to .gmem_reclaim_memory()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [Critical] Failure to leak a page after an RMP transition error in sev_gmem_reclaim_memory allows hypervisor-owned pages to be unsafely returned to the host page allocator.
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commit c2f5753d0289e9cb80f17e6494a0d03b0f6a529a
Author: Sean Christopherson <seanjc@google.com>

KVM: Rename .gmem_invalidate() to .gmem_reclaim_memory()

Rename the .gmem_invalidate() hook to .gmem_reclaim_memory() since it is
called when a folio is freed, which is too late to invalidate memory usage.
Keep guest_memfd's trampoline and opportunistically guard the callback with
an ifdef.

> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 30792adcfc8e5..4465e75494f2d 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -5136,7 +5136,7 @@ int sev_gmem_prepare(struct kvm *kvm, kvm_pfn_t pfn, gfn_t gfn, int max_order)
>  	return 0;
>  }
>  
> -void sev_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end)
> +void sev_gmem_reclaim_memory(kvm_pfn_t start, kvm_pfn_t end)
>  {

[Severity: Critical]
This is a pre-existing issue, but does failing to leak the page on RMP update
errors allow it to be unsafely returned to the host allocator?

In sev_gmem_reclaim_memory(), if rmp_make_shared() fails, the code logs a
warning and proceeds to the next PFN:

    rc = rmp_make_shared(pfn, use_2m_update ? PG_LEVEL_2M : PG_LEVEL_4K);
    if (WARN_ONCE(rc, "SEV: Failed to update RMP entry ..."))
        goto next_pfn;

By jumping to next_pfn instead of calling snp_leak_pages(), the
hypervisor-owned page could be freed back to the host allocator.

Could this trigger a hardware RMP violation and a host panic upon the page's
next use? A later patch in the series fixes a guest-triggerable vector for
this failure, but the structural issue remains.

>  	kvm_pfn_t pfn;
>

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Sashiko AI review · https://sashiko.dev/#/patchset/20260630222607.497895-1-seanjc@google.com?part=4