Messages in this thread | | | Subject | Re: [PATCH] KVM: nSVM: Optimize L12 to L2 vmcb.save copies | From | Cathy Avery <> | Date | Tue, 2 Mar 2021 07:56:31 -0500 |
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On 3/1/21 7:59 PM, Sean Christopherson wrote: > On Mon, Mar 01, 2021, Cathy Avery wrote: >> kvm_set_rflags(&svm->vcpu, vmcb12->save.rflags | X86_EFLAGS_FIXED); >> svm_set_efer(&svm->vcpu, vmcb12->save.efer); >> svm_set_cr0(&svm->vcpu, vmcb12->save.cr0); >> svm_set_cr4(&svm->vcpu, vmcb12->save.cr4); > Why not utilize VMCB_CR? I was going to tackle CR in a follow up patch. I should have mentioned that but it makes sense to go ahead and do it now. > >> - svm->vcpu.arch.cr2 = vmcb12->save.cr2; >> + svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = vmcb12->save.cr2; > Same question for VMCB_CR2. > > Also, isn't writing svm->vmcb->save.cr2 unnecessary since svm_vcpu_run() > unconditionally writes it? > > Alternatively, it shouldn't be too much work to add proper dirty tracking for > CR2. VMX has to write the real CR2 every time because there's no VMCS field, > but I assume can avoid the write and dirty update on the majority of VMRUNs.
I 'll take a look at CR2 as well.
Thanks for the feedback,
Cathy
> >> + >> kvm_rax_write(&svm->vcpu, vmcb12->save.rax); >> kvm_rsp_write(&svm->vcpu, vmcb12->save.rsp); >> kvm_rip_write(&svm->vcpu, vmcb12->save.rip); >> >> /* In case we don't even reach vcpu_run, the fields are not updated */ >> - svm->vmcb->save.cr2 = svm->vcpu.arch.cr2; >> svm->vmcb->save.rax = vmcb12->save.rax; >> svm->vmcb->save.rsp = vmcb12->save.rsp; >> svm->vmcb->save.rip = vmcb12->save.rip; >> >> - svm->vmcb->save.dr7 = vmcb12->save.dr7 | DR7_FIXED_1; >> - svm->vcpu.arch.dr6 = vmcb12->save.dr6 | DR6_ACTIVE_LOW; >> - vmcb_mark_dirty(svm->vmcb, VMCB_DR); >> + /* These bits will be set properly on the first execution when new_vmc12 is true */ >> + if (unlikely(new_vmcb12 || vmcb_is_dirty(vmcb12, VMCB_DR))) { >> + svm->vmcb->save.dr7 = vmcb12->save.dr7 | DR7_FIXED_1; >> + svm->vcpu.arch.dr6 = vmcb12->save.dr6 | DR6_ACTIVE_LOW; >> + vmcb_mark_dirty(svm->vmcb, VMCB_DR); >> + } >> } >> >> static void nested_vmcb02_prepare_control(struct vcpu_svm *svm) >> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c >> index 54610270f66a..9761a7ca8100 100644 >> --- a/arch/x86/kvm/svm/svm.c >> +++ b/arch/x86/kvm/svm/svm.c >> @@ -1232,6 +1232,7 @@ static void init_vmcb(struct kvm_vcpu *vcpu) >> svm->asid = 0; >> >> svm->nested.vmcb12_gpa = 0; >> + svm->nested.last_vmcb12_gpa = 0; > We should use INVALID_PAGE, '0' is a legal physical address and could > theoretically get a false negative on the "new_vmcb12" check. > >> vcpu->arch.hflags = 0; >> >> if (!kvm_pause_in_guest(vcpu->kvm)) { >> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h >> index fbbb26dd0f73..911868d4584c 100644 >> --- a/arch/x86/kvm/svm/svm.h >> +++ b/arch/x86/kvm/svm/svm.h >> @@ -93,6 +93,7 @@ struct svm_nested_state { >> u64 hsave_msr; >> u64 vm_cr_msr; >> u64 vmcb12_gpa; >> + u64 last_vmcb12_gpa; >> >> /* These are the merged vectors */ >> u32 *msrpm; >> @@ -247,6 +248,11 @@ static inline void vmcb_mark_dirty(struct vmcb *vmcb, int bit) >> vmcb->control.clean &= ~(1 << bit); >> } >> >> +static inline bool vmcb_is_dirty(struct vmcb *vmcb, int bit) >> +{ >> + return !test_bit(bit, (unsigned long *)&vmcb->control.clean); >> +} >> + >> static inline struct vcpu_svm *to_svm(struct kvm_vcpu *vcpu) >> { >> return container_of(vcpu, struct vcpu_svm, vcpu); >> -- >> 2.26.2 >>
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