Re: [PATCH v3 03/11] KVM: x86: retry non-page-table writing instruction

Avi Kivity
2011-09-13T10:47:56Z

On 08/30/2011 05:35 AM, Xiao Guangrong wrote:
> If the emulation is caused by #PF and it is non-page_table writing instruction,
> it means the VM-EXIT is caused by shadow page protected, we can zap the shadow
> page and retry this instruction directly
>
> The idea is from Avi
>
>
> int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len);
> +bool page_table_writing_insn(struct x86_emulate_ctxt *ctxt);

Please use the usual x86_ prefix used in the emulator interface.

> @@ -3720,10 +3721,18 @@ void __kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
> kvm_mmu_commit_zap_page(vcpu->kvm,&invalid_list);
> }
>
> +static bool is_mmio_page_fault(struct kvm_vcpu *vcpu, gva_t addr)
> +{
> + if (vcpu->arch.mmu.direct_map || mmu_is_nested(vcpu))
> + return vcpu_match_mmio_gpa(vcpu, addr);
> +
> + return vcpu_match_mmio_gva(vcpu, addr);
> +}
> +
> int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
> void *insn, int insn_len)
> {
> - int r;
> + int r, emulation_type = EMULTYPE_RETRY;
> enum emulation_result er;
>
> r = vcpu->arch.mmu.page_fault(vcpu, cr2, error_code, false);
> @@ -3735,7 +3744,10 @@ int kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gva_t cr2, u32 error_code,
> goto out;
> }
>
> - er = x86_emulate_instruction(vcpu, cr2, 0, insn, insn_len);
> + if (is_mmio_page_fault(vcpu, cr2))
> + emulation_type = 0;
> +
> + er = x86_emulate_instruction(vcpu, cr2, emulation_type, insn, insn_len);
>
> switch (er) {
> case EMULATE_DONE:
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 6b37f18..1afe59e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -4814,6 +4814,50 @@ static bool reexecute_instruction(struct kvm_vcpu *vcpu, gva_t gva)
> return false;
> }
>
> +static bool retry_instruction(struct x86_emulate_ctxt *ctxt,
> + unsigned long cr2, int emulation_type)
> +{
> + if (!vcpu->arch.mmu.direct_map&& !mmu_is_nested(vcpu))
> + gpa = kvm_mmu_gva_to_gpa_write(vcpu, cr2, NULL);

If mmu_is_nested() cr2 is an ngpa, we have to translate it to a gpa, no?

btw, I don't see mmu.direct_map initialized for nested npt?

> +
> + kvm_mmu_unprotect_page(vcpu->kvm, gpa>> PAGE_SHIFT);
> +
> + return true;
> +}
> +
> int x86_emulate_instruction(struct kvm_vcpu *vcpu,
> unsigned long cr2,
> int emulation_type,
> @@ -4855,6 +4899,9 @@ int x86_emulate_instruction(struct kvm_vcpu *vcpu,
> return EMULATE_DONE;
> }
>
> + if (retry_instruction(ctxt, cr2, emulation_type))
> + return EMULATE_DONE;
> +
> /* this is needed for vmware backdoor interface to work since it
> changes registers values during IO operation */
> if (vcpu->arch.emulate_regs_need_sync_from_vcpu) {

--
error compiling committee.c: too many arguments to function