Messages in this thread | | | Date | Mon, 2 May 2022 21:07:44 +0700 | Subject | Re: [PATCH v2 08/12] KVM: SVM: Update AVIC settings when changing APIC mode | From | Suravee Suthikulpanit <> |
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Maxim, Sean
On 4/18/22 7:55 PM, Maxim Levitsky wrote: > On Tue, 2022-04-12 at 06:58 -0500, Suravee Suthikulpanit wrote: >> When APIC mode is updated (e.g. disabled, xAPIC, or x2APIC), >> KVM needs to call kvm_vcpu_update_apicv() to update AVIC settings >> accordingly. >> >> Signed-off-by: Suravee Suthikulpanit<suravee.suthikulpanit@amd.com> >> --- >> arch/x86/kvm/svm/avic.c | 15 +++++++++++++++ >> arch/x86/kvm/svm/svm.c | 1 + >> 2 files changed, 16 insertions(+) >> >> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c >> index 22ee1098e2a5..01392b8364f4 100644 >> --- a/arch/x86/kvm/svm/avic.c >> +++ b/arch/x86/kvm/svm/avic.c >> @@ -616,6 +616,21 @@ void avic_apicv_post_state_restore(struct kvm_vcpu *vcpu) >> avic_handle_ldr_update(vcpu); >> } >> >> +void avic_set_virtual_apic_mode(struct kvm_vcpu *vcpu) >> +{ >> + struct vcpu_svm *svm = to_svm(vcpu); >> + >> + if (!lapic_in_kernel(vcpu) || (avic_mode == AVIC_MODE_NONE)) >> + return; >> + >> + if (kvm_get_apic_mode(vcpu) == LAPIC_MODE_INVALID) { >> + WARN_ONCE(true, "Invalid local APIC state (vcpu_id=%d)", vcpu->vcpu_id); >> + return; >> + } >> + >> + kvm_vcpu_update_apicv(&svm->vcpu); > I think it makes sense to call avic_refresh_apicv_exec_ctrl directly here. > > I am not sure that kvm_vcpu_update_apicv will even call it > because it has an optimization of doing nothing when inhibition status > didn't change. > > > Another semi-related note: > > the current way the x2avic msrs are configured creates slight performance > problem for nesting: > > The problem is that when entering a nested guest, AVIC on the current vCPU > is inhibited, but this is done only so that this vCPU*peers* don't > try to use AVIC to send IPIs to it, so there is no need to update vmcb01 > msr interception bitmap, and vmcb02 should have all these msrs intercepted always. > Same with returning to host. > > It also should be checked that during nested entry, at least vmcb01 msr bitmap > is updated - TL;DR - please check that x2avic works when there is a nested guest running.
In the kvm/queue branch, I found a regression on nested SVM guest, where L2 guest cannot launch. The bad commit is:
commit a4cfff3f0f8c07f1f7873a82bdeb3995807dac8c (bisect) Merge: 42dcbe7d8bac 8d5678a76689 Author: Paolo Bonzini <pbonzini@redhat.com> Date: Fri Apr 8 12:43:40 2022 -0400
Merge branch 'kvm-older-features' into HEAD
Merge branch for features that did not make it into 5.18:
* New ioctls to get/set TSC frequency for a whole VM
* Allow userspace to opt out of hypercall patching
Nested virtualization improvements for AMD:
* Support for "nested nested" optimizations (nested vVMLOAD/VMSAVE, nested vGIF)
* Allow AVIC to co-exist with a nested guest running
* Fixes for LBR virtualizations when a nested guest is running, and nested LBR virtualization support
* PAUSE filtering for nested hypervisors
Guest support:
* Decoupling of vcpu_is_preempted from PV spinlocks
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
I am still working on the bisect into the merge commits.
Regards, Suravee
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