On Thu, Sep 04, 2014 at 07:44:51PM +0200, Paolo Bonzini wrote:
> Il 04/09/2014 17:05, Gleb Natapov ha scritto:
> >> >
> >> > If you do that, KVM gets down to the "if (writeback)" and writes the
> >> > ctxt->eip from L2 into the L1 EIP.
> > Heh, that's a bummer. We should not write back if an instruction caused a
> > vmexit.
> >
>
> You're right, that works.
Looks good!
Reviewed-by: Gleb Natapov <g...@kernel.org>
>
> Paolo
>
> -------------- 8< -------------
> Subject: [PATCH] KVM: x86: skip writeback on injection of nested exception
>
> If a nested page fault happens during emulation, we will inject a vmexit,
> not a page fault. However because writeback happens after the injection,
> we will write ctxt->eip from L2 into the L1 EIP. We do not write back
> if an instruction caused an interception vmexit---do the same for page
> faults.
>
> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
> ---
> arch/x86/include/asm/kvm_host.h | 1 -
> arch/x86/kvm/x86.c | 15 ++++++++++-----
> 2 files changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 08cc299..c989651 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -893,7 +893,6 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct
> x86_exception *fault);
> int kvm_read_guest_page_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> gfn_t gfn, void *data, int offset, int len,
> u32 access);
> -void kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault);
> bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);
>
> static inline int __kvm_irq_line_state(unsigned long *irq_state,
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index e4ed85e..3541946 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -408,12 +408,14 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu,
> struct x86_exception *fault)
> }
> EXPORT_SYMBOL_GPL(kvm_inject_page_fault);
>
> -void kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault)
> +static bool kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception
> *fault)
> {
> if (mmu_is_nested(vcpu) && !fault->nested_page_fault)
> vcpu->arch.nested_mmu.inject_page_fault(vcpu, fault);
> else
> vcpu->arch.mmu.inject_page_fault(vcpu, fault);
> +
> + return fault->nested_page_fault;
> }
>
> void kvm_inject_nmi(struct kvm_vcpu *vcpu)
> @@ -4929,16 +4931,18 @@ static void toggle_interruptibility(struct kvm_vcpu
> *vcpu, u32 mask)
> }
> }
>
> -static void inject_emulated_exception(struct kvm_vcpu *vcpu)
> +static bool inject_emulated_exception(struct kvm_vcpu *vcpu)
> {
> struct x86_emulate_ctxt *ctxt = &vcpu->arch.emulate_ctxt;
> if (ctxt->exception.vector == PF_VECTOR)
> - kvm_propagate_fault(vcpu, &ctxt->exception);
> - else if (ctxt->exception.error_code_valid)
> + return kvm_propagate_fault(vcpu, &ctxt->exception);
> +
> + if (ctxt->exception.error_code_valid)
> kvm_queue_exception_e(vcpu, ctxt->exception.vector,
> ctxt->exception.error_code);
> else
> kvm_queue_exception(vcpu, ctxt->exception.vector);
> + return false;
> }
>
> static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
> @@ -5300,8 +5304,9 @@ restart:
> }
>
> if (ctxt->have_exception) {
> - inject_emulated_exception(vcpu);
> r = EMULATE_DONE;
> + if (inject_emulated_exception(vcpu))
> + return r;
> } else if (vcpu->arch.pio.count) {
> if (!vcpu->arch.pio.in) {
> /* FIXME: return into emulator if single-stepping. */
> --
> 1.9.3
>
>
--
Gleb.
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