Re: [PATCH 2/3] KVM: x86: let reexecute_instruction work for tdp

Marcelo Tosatti
2012-11-26T22:37:12Z

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