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    Subject[PATCH RFC v7 61/64] KVM: SVM: Make VMSAVE target area memory allocation SNP safe
    Date
    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.

    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 543261c87eb3..1d4a723d5def 100644
    --- a/arch/x86/kvm/svm/svm.c
    +++ b/arch/x86/kvm/svm/svm.c
    @@ -653,7 +653,7 @@ 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;

    --
    2.25.1
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