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    SubjectRe: [PATCH RFC v8 53/56] KVM: SVM: Make VMSAVE target area memory allocation SNP safe
    On Mon, 20 Feb 2023 12:38:44 -0600
    Michael Roth <michael.roth@amd.com> wrote:

    > From: Ashish Kalra <ashish.kalra@amd.com>
    >
    > Implement a workaround for an SNP erratum where the CPU will incorrectly
    > signal an RMP violation #PF if a hugepage (2mb or 1gb) collides with the
    > RMP entry of the VMSAVE target page.
    >
    > When SEV-SNP is globally enabled, the CPU marks the VMSAVE target page
    > as "InUse" while the VMSAVE instruction is executing. If another
    > CPU writes to a different page in the same 2MB region while the VMSAVE
    > is executing, the CPU will throw an RMP violation #PF.
    >
    > Use the snp safe generic allocator for allocating the VMSA target
    > page which will ensure that the page returned is not a hugepage, as it
    > is already being used for the allocating the VMCB, VMSA and AVIC backing
    > page.
    >

    This should be merged with patch where implements the snp_safe_alloc_page().

    > Co-developed-by: Marc Orr <marcorr@google.com>
    > Signed-off-by: Marc Orr <marcorr@google.com>
    > Reported-by: Alper Gun <alpergun@google.com>
    > Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
    > Signed-off-by: Michael Roth <michael.roth@amd.com>
    > ---
    > arch/x86/kvm/svm/svm.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
    > index 3fe5f13b5f3a..8bda31a61757 100644
    > --- a/arch/x86/kvm/svm/svm.c
    > +++ b/arch/x86/kvm/svm/svm.c
    > @@ -665,7 +665,7 @@ static int svm_cpu_init(int cpu)
    > int ret = -ENOMEM;
    >
    > memset(sd, 0, sizeof(struct svm_cpu_data));
    > - sd->save_area = alloc_page(GFP_KERNEL | __GFP_ZERO);
    > + sd->save_area = snp_safe_alloc_page(NULL);
    > if (!sd->save_area)
    > return ret;
    >

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