On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote: > Always mark the AVIC as "running" on vCPU load when the AVIC is enabled and > drop the vcpu_blocking/unblocking hooks that toggle "running". There is no > harm in keeping the flag set for a wee bit longer when a vCPU is blocking, > i.e. between the start of blocking and being scheduled out. At worst, an > agent in the host will unnecessarily signal the doorbell, but that's > already the status quo in KVM as the "running" flag is set the entire time > a vCPU is loaded, not just when it's actively running the guest. > > In addition to simplifying the code, keeping the "running" flag set longer > can reduce the number of VM-Exits due to incomplete IPI delivery. > > Signed-off-by: Sean Christopherson <[email protected]> > --- > arch/x86/kvm/svm/avic.c | 53 +++++++++++++---------------------------- > arch/x86/kvm/svm/svm.c | 8 ------- > arch/x86/kvm/svm/svm.h | 3 --- > 3 files changed, 17 insertions(+), 47 deletions(-) > > diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c > index b43b05610ade..213f5223f63e 100644 > --- a/arch/x86/kvm/svm/avic.c > +++ b/arch/x86/kvm/svm/avic.c > @@ -967,6 +967,15 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > int h_physical_id = kvm_cpu_get_apicid(cpu); > struct vcpu_svm *svm = to_svm(vcpu); > > + /* TODO: Document why the unblocking path checks for updates. */ > + if (kvm_vcpu_is_blocking(vcpu) && > + kvm_check_request(KVM_REQ_APICV_UPDATE, vcpu)) { > + kvm_vcpu_update_apicv(vcpu); > + > + if (!kvm_vcpu_apicv_active(vcpu)) > + return; > + } > + > /* > * Since the host physical APIC id is 8 bits, > * we can support host APIC ID upto 255. > @@ -974,19 +983,21 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) > if (WARN_ON(h_physical_id > > AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK)) > return; > > + /* > + * Unconditionally mark the AVIC as "running", even if the vCPU is in > + * kvm_vcpu_block(). kvm_vcpu_check_block() will detect pending IRQs > + * and bail out of the block loop, and if not, avic_vcpu_put() will > + * set the AVIC back to "not running" when the vCPU is scheduled out. > + */ > entry = READ_ONCE(*(svm->avic_physical_id_cache)); > WARN_ON(entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK); > > entry &= ~AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK; > entry |= (h_physical_id & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK); > - > - entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK; > - if (svm->avic_is_running) > - entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK; > + entry |= AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK; > > WRITE_ONCE(*(svm->avic_physical_id_cache), entry); > - avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, > - svm->avic_is_running); > + avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, true); > } > > void avic_vcpu_put(struct kvm_vcpu *vcpu) > @@ -1001,33 +1012,3 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu) > entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK; > WRITE_ONCE(*(svm->avic_physical_id_cache), entry); > } > - > -/* > - * This function is called during VCPU halt/unhalt. > - */ > -static void avic_set_running(struct kvm_vcpu *vcpu, bool is_run) > -{ > - struct vcpu_svm *svm = to_svm(vcpu); > - > - svm->avic_is_running = is_run; > - > - if (!kvm_vcpu_apicv_active(vcpu)) > - return; > - > - if (is_run) > - avic_vcpu_load(vcpu, vcpu->cpu); > - else > - avic_vcpu_put(vcpu); > -} > - > -void svm_vcpu_blocking(struct kvm_vcpu *vcpu) > -{ > - avic_set_running(vcpu, false); > -} > - > -void svm_vcpu_unblocking(struct kvm_vcpu *vcpu) > -{ > - if (kvm_check_request(KVM_REQ_APICV_UPDATE, vcpu)) > - kvm_vcpu_update_apicv(vcpu); > - avic_set_running(vcpu, true); > -} > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c > index 89077160d463..a1ca5707f2c8 100644 > --- a/arch/x86/kvm/svm/svm.c > +++ b/arch/x86/kvm/svm/svm.c > @@ -1433,12 +1433,6 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu) > if (err) > goto error_free_vmsa_page; > > - /* We initialize this flag to true to make sure that the is_running > - * bit would be set the first time the vcpu is loaded. > - */ > - if (irqchip_in_kernel(vcpu->kvm) && kvm_apicv_activated(vcpu->kvm)) > - svm->avic_is_running = true; > - > svm->msrpm = svm_vcpu_alloc_msrpm(); > if (!svm->msrpm) { > err = -ENOMEM; > @@ -4597,8 +4591,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { > .prepare_guest_switch = svm_prepare_guest_switch, > .vcpu_load = svm_vcpu_load, > .vcpu_put = svm_vcpu_put, > - .vcpu_blocking = svm_vcpu_blocking, > - .vcpu_unblocking = svm_vcpu_unblocking, > > .update_exception_bitmap = svm_update_exception_bitmap, > .get_msr_feature = svm_get_msr_feature, > diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h > index 7f5b01bbee29..652d71acfb6c 100644 > --- a/arch/x86/kvm/svm/svm.h > +++ b/arch/x86/kvm/svm/svm.h > @@ -169,7 +169,6 @@ struct vcpu_svm { > u32 dfr_reg; > struct page *avic_backing_page; > u64 *avic_physical_id_cache; > - bool avic_is_running; > > /* > * Per-vcpu list of struct amd_svm_iommu_ir: > @@ -529,8 +528,6 @@ int svm_deliver_avic_intr(struct kvm_vcpu *vcpu, int vec); > bool svm_dy_apicv_has_pending_interrupt(struct kvm_vcpu *vcpu); > int svm_update_pi_irte(struct kvm *kvm, unsigned int host_irq, > uint32_t guest_irq, bool set); > -void svm_vcpu_blocking(struct kvm_vcpu *vcpu); > -void svm_vcpu_unblocking(struct kvm_vcpu *vcpu); > > /* sev.c */ >
Looks good. It is nice to get rid of all of this logic that was just making things more complicated. Something else nice to do here which I didn't finish back then when I worked on avic, would be to maybe rename avic_vcpu_load/avic_vcpu_put because those are also now run on avic inhibit/uninhibit. Basically the 'svm_refresh_apicv_exec_ctrl' is the full avic activate/deactivate, while avic_vcpu_load/avic_vcpu_put are the lighter weight partial avic activation/deactivation functions. So minus the comment from Paolo about the updating avic on unblock which I missed back when I wrote my patches: Reviewed-by: Maxim Levitsky <[email protected]> Best regards, Maxim Levitsky _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
