From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 3/4] KVM: x86: inject nested page faults on emulated instructions Date: Thu, 04 Sep 2014 19:44:51 +0200 Message-ID: <5408A513.6090603@redhat.com> References: <1409670830-14544-1-git-send-email-pbonzini@redhat.com> <1409670830-14544-4-git-send-email-pbonzini@redhat.com> <20140904070220.GL9842@cloudius-systems.com> <54087343.5050409@redhat.com> <20140904150500.GA25317@minantech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Cc: Gleb Natapov , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, jroedel@suse.de, agraf@suse.de, valentine.sinitsyn@gmail.com, jan.kiszka@siemens.com, avi@cloudius-systems.com To: Gleb Natapov Return-path: In-Reply-To: <20140904150500.GA25317@minantech.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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. 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 --- 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