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    Subject[PATCH 5.16 051/200] KVM: x86: nSVM: skip eax alignment check for non-SVM instructions
    Date
    From: Denis Valeev <lemniscattaden@gmail.com>

    commit 47c28d436f409f5b009dc82bd82d4971088aa391 upstream.

    The bug occurs on #GP triggered by VMware backdoor when eax value is
    unaligned. eax alignment check should not be applied to non-SVM
    instructions because it leads to incorrect omission of the instructions
    emulation.
    Apply the alignment check only to SVM instructions to fix.

    Fixes: d1cba6c92237 ("KVM: x86: nSVM: test eax for 4K alignment for GP errata workaround")
    Signed-off-by: Denis Valeev <lemniscattaden@gmail.com>
    Message-Id: <Yexlhaoe1Fscm59u@q>
    Cc: stable@vger.kernel.org
    Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/x86/kvm/svm/svm.c | 11 ++++++-----
    1 file changed, 6 insertions(+), 5 deletions(-)

    --- a/arch/x86/kvm/svm/svm.c
    +++ b/arch/x86/kvm/svm/svm.c
    @@ -2306,10 +2306,6 @@ static int gp_interception(struct kvm_vc
    if (error_code)
    goto reinject;

    - /* All SVM instructions expect page aligned RAX */
    - if (svm->vmcb->save.rax & ~PAGE_MASK)
    - goto reinject;
    -
    /* Decode the instruction for usage later */
    if (x86_decode_emulated_instruction(vcpu, 0, NULL, 0) != EMULATION_OK)
    goto reinject;
    @@ -2327,8 +2323,13 @@ static int gp_interception(struct kvm_vc
    if (!is_guest_mode(vcpu))
    return kvm_emulate_instruction(vcpu,
    EMULTYPE_VMWARE_GP | EMULTYPE_NO_DECODE);
    - } else
    + } else {
    + /* All SVM instructions expect page aligned RAX */
    + if (svm->vmcb->save.rax & ~PAGE_MASK)
    + goto reinject;
    +
    return emulate_svm_instr(vcpu, opcode);
    + }

    reinject:
    kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);

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