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    SubjectRe: [PATCH 2/3] KVM: x86: let reexecute_instruction work for tdp
    On Tue, Nov 20, 2012 at 07:59:10AM +0800, Xiao Guangrong wrote:
    > Currently, reexecute_instruction refused to retry all instructions. If
    > nested npt is used, the emulation may be caused by shadow page, it can
    > be fixed by dropping the shadow page
    >
    > Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
    > ---
    > arch/x86/kvm/x86.c | 14 ++++++++------
    > 1 files changed, 8 insertions(+), 6 deletions(-)
    >
    > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
    > index 7be8452..5fe72cc 100644
    > --- a/arch/x86/kvm/x86.c
    > +++ b/arch/x86/kvm/x86.c
    > @@ -4469,17 +4469,19 @@ static int handle_emulation_failure(struct kvm_vcpu *vcpu)
    > return r;
    > }
    >
    > -static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t gva)
    > +static bool reexecute_instruction(struct kvm_vcpu *vcpu, unsigned long cr2)
    > {
    > - gpa_t gpa;
    > + gpa_t gpa = cr2;
    > pfn_t pfn;
    >
    > - if (tdp_enabled)
    > + if (!ACCESS_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
    > return false;

    How is indirect_shadow_pages protected? Why is ACCESS_ONCE() being used
    to read it?

    > - gpa = kvm_mmu_gva_to_gpa_read(vcpu, gva, NULL);
    > - if (gpa == UNMAPPED_GVA)
    > - return true; /* let cpu generate fault */
    > + if (!vcpu->arch.mmu.direct_map) {
    > + gpa = kvm_mmu_gva_to_gpa_read(vcpu, cr2, NULL);
    > + if (gpa == UNMAPPED_GVA)
    > + return true; /* let cpu generate fault */
    > + }
    >
    > /*
    > * if emulation was due to access to shadowed page table
    > --
    > 1.7.7.6


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