On 07/10/2012 06:57 AM, Xiao Guangrong wrote: > On 07/10/2012 01:05 AM, Avi Kivity wrote: > > Currently we check that the mmu root exits before every entry. Use the > > existing KVM_REQ_MMU_RELOAD mechanism instead, by making it really reload > > the mmu, and by adding the request to mmu initialization code. > > > > Signed-off-by: Avi Kivity <[email protected]> > > --- > > arch/x86/kvm/mmu.c | 4 +++- > > arch/x86/kvm/svm.c | 1 + > > arch/x86/kvm/x86.c | 13 +++++++------ > > 3 files changed, 11 insertions(+), 7 deletions(-) > > > > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > > index 569cd66..136d757 100644 > > --- a/arch/x86/kvm/mmu.c > > +++ b/arch/x86/kvm/mmu.c > > @@ -3180,7 +3180,8 @@ void kvm_mmu_flush_tlb(struct kvm_vcpu *vcpu) > > static void paging_new_cr3(struct kvm_vcpu *vcpu) > > { > > pgprintk("%s: cr3 %lx\n", __func__, kvm_read_cr3(vcpu)); > > - mmu_free_roots(vcpu); > > + kvm_mmu_unload(vcpu); > > + kvm_mmu_load(vcpu); > > } > > > > static unsigned long get_cr3(struct kvm_vcpu *vcpu) > > @@ -3469,6 +3470,7 @@ static int init_kvm_nested_mmu(struct kvm_vcpu *vcpu) > > > > static int init_kvm_mmu(struct kvm_vcpu *vcpu) > > { > > + kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu); > > if (mmu_is_nested(vcpu)) > > return init_kvm_nested_mmu(vcpu); > > else if (tdp_enabled) > > diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c > > index 7a41878..d77ad8c 100644 > > --- a/arch/x86/kvm/svm.c > > +++ b/arch/x86/kvm/svm.c > > @@ -2523,6 +2523,7 @@ static bool nested_svm_vmrun(struct vcpu_svm *svm) > > > > if (nested_vmcb->control.nested_ctl) { > > kvm_mmu_unload(&svm->vcpu); > > + kvm_make_request(KVM_REQ_MMU_RELOAD, &svm->vcpu); > > svm->nested.nested_cr3 = nested_vmcb->control.nested_cr3; > > nested_svm_init_mmu_context(&svm->vcpu); > > } > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index 959e5a9..162231f 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -5226,8 +5226,14 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) > > kvm_make_request(KVM_REQ_EVENT, vcpu); > > > > if (vcpu->requests) { > > - if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) > > + if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) { > > kvm_mmu_unload(vcpu); > > + r = kvm_mmu_reload(vcpu); > > + if (unlikely(r)) { > > + kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu); > > + goto out; > > + } > > Now, reload mmu is before event injecting, can below bug be triggered again? > > commit d8368af8b46b904def42a0f341d2f4f29001fa77 > Author: Avi Kivity <[email protected]> > Date: Mon May 14 18:07:56 2012 +0300 > > KVM: Fix mmu_reload() clash with nested vmx event injection > > Currently the inject_pending_event() call during guest entry happens after > kvm_mmu_reload(). This is for historical reasons - we used to > inject_pending_event() in atomic context, while kvm_mmu_reload() needs > task > context. > > A problem is that nested vmx can cause the mmu context to be reset, if > event > injection is intercepted and causes a #VMEXIT instead (the #VMEXIT resets > CR0/CR3/CR4). If this happens, we end up with invalid root_hpa, and since > kvm_mmu_reload() has already run, no one will fix it and we end up > entering > the guest this way. > > Fix by reordering event injection to be before kvm_mmu_reload(). Use > ->cancel_injection() to undo if kvm_mmu_reload() fails. >
I haven't considered it, but I think the patch is safe. If init_kvm_mmu() is called as part of event injection then it will set KVM_REQ_MMU_RELOAD and we will process the requests again before entering the guest. -- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
