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    Subject[patch 17/71] KVM: SVM: fix random segfaults with NPT enabled

    2.6.26-stable review patch. If anyone has any objections, please let us
    know.

    ------------------
    From: Joerg Roedel <joerg.roedel@amd.com>

    (cherry picked from commit 44874f84918e37b64bec6df1587e5fe2fdf6ab62)

    This patch introduces a guest TLB flush on every NPF exit in KVM. This fixes
    random segfaults and #UD exceptions in the guest seen under some workloads
    (e.g. long running compile workloads or tbench). A kernbench run with and
    without that fix showed that it has a slowdown lower than 0.5%

    Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
    Signed-off-by: Alexander Graf <agraf@suse.de>
    Signed-off-by: Avi Kivity <avi@qumranet.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    arch/x86/kvm/svm.c | 10 ++++++++++
    1 file changed, 10 insertions(+)

    --- a/arch/x86/kvm/svm.c
    +++ b/arch/x86/kvm/svm.c
    @@ -60,6 +60,7 @@ static int npt = 1;
    module_param(npt, int, S_IRUGO);

    static void kvm_reput_irq(struct vcpu_svm *svm);
    +static void svm_flush_tlb(struct kvm_vcpu *vcpu);

    static inline struct vcpu_svm *to_svm(struct kvm_vcpu *vcpu)
    {
    @@ -1017,6 +1018,15 @@ static int pf_interception(struct vcpu_s

    fault_address = svm->vmcb->control.exit_info_2;
    error_code = svm->vmcb->control.exit_info_1;
    +
    + /*
    + * FIXME: Tis shouldn't be necessary here, but there is a flush
    + * missing in the MMU code. Until we find this bug, flush the
    + * complete TLB here on an NPF
    + */
    + if (npt_enabled)
    + svm_flush_tlb(&svm->vcpu);
    +
    if (event_injection)
    kvm_mmu_unprotect_page_virt(&svm->vcpu, fault_address);
    return kvm_mmu_page_fault(&svm->vcpu, fault_address, error_code);
    --


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