[PATCH v3 40/62] iommu/amd: KVM: SVM: Infer IsRun from validity of pCPU destination
From: Sean Christopherson <seanjc@google.com>
Date: 2025-06-11 22:48:05
Also in:
kvm, kvmarm, linux-iommu, lkml
Subsystem:
amd iommu (amd-vi), iommu subsystem, kernel virtual machine for x86 (kvm/x86), the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Joerg Roedel, Will Deacon, Sean Christopherson, Paolo Bonzini, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Infer whether or not a vCPU should be marked running from the validity of the pCPU on which it is running. amd_iommu_update_ga() already skips the IRTE update if the pCPU is invalid, i.e. passing %true for is_run with an invalid pCPU would be a blatant and egregrious KVM bug. Tested-by: Sairaj Kodilkar <redacted> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/svm/avic.c | 11 +++++------ drivers/iommu/amd/iommu.c | 14 +++++++++----- include/linux/amd-iommu.h | 6 ++---- 3 files changed, 16 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 4747fb09aca4..c79648d96752 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c@@ -832,7 +832,7 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm, entry = svm->avic_physical_id_entry; if (entry & AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK) amd_iommu_update_ga(entry & AVIC_PHYSICAL_ID_ENTRY_HOST_PHYSICAL_ID_MASK, - true, pi_data.ir_data); + pi_data.ir_data); irqfd->irq_bypass_data = pi_data.ir_data; list_add(&irqfd->vcpu_list, &svm->ir_list);
@@ -841,8 +841,7 @@ int avic_pi_update_irte(struct kvm_kernel_irqfd *irqfd, struct kvm *kvm, return irq_set_vcpu_affinity(host_irq, NULL); } -static inline int -avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu, bool r) +static inline int avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu) { int ret = 0; struct vcpu_svm *svm = to_svm(vcpu);
@@ -861,7 +860,7 @@ avic_update_iommu_vcpu_affinity(struct kvm_vcpu *vcpu, int cpu, bool r) return 0; list_for_each_entry(irqfd, &svm->ir_list, vcpu_list) { - ret = amd_iommu_update_ga(cpu, r, irqfd->irq_bypass_data); + ret = amd_iommu_update_ga(cpu, irqfd->irq_bypass_data); if (ret) return ret; }
@@ -923,7 +922,7 @@ void avic_vcpu_load(struct kvm_vcpu *vcpu, int cpu) WRITE_ONCE(kvm_svm->avic_physical_id_table[vcpu->vcpu_id], entry); - avic_update_iommu_vcpu_affinity(vcpu, h_physical_id, true); + avic_update_iommu_vcpu_affinity(vcpu, h_physical_id); spin_unlock_irqrestore(&svm->ir_list_lock, flags); }
@@ -963,7 +962,7 @@ void avic_vcpu_put(struct kvm_vcpu *vcpu) */ spin_lock_irqsave(&svm->ir_list_lock, flags); - avic_update_iommu_vcpu_affinity(vcpu, -1, 0); + avic_update_iommu_vcpu_affinity(vcpu, -1); entry &= ~AVIC_PHYSICAL_ID_ENTRY_IS_RUNNING_MASK; svm->avic_physical_id_entry = entry;
diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 5adc932b947e..bb804bbc916b 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c@@ -3990,15 +3990,17 @@ int amd_iommu_create_irq_domain(struct amd_iommu *iommu) * Update the pCPU information for an IRTE that is configured to post IRQs to * a vCPU, without issuing an IOMMU invalidation for the IRTE. * - * This API is intended to be used when a vCPU is scheduled in/out (or stops - * running for any reason), to do a fast update of IsRun and (conditionally) - * Destination. + * If the vCPU is associated with a pCPU (@cpu >= 0), configure the Destination + * with the pCPU's APIC ID and set IsRun, else clear IsRun. I.e. treat vCPUs + * that are associated with a pCPU as running. This API is intended to be used + * when a vCPU is scheduled in/out (or stops running for any reason), to do a + * fast update of IsRun and (conditionally) Destination. * * Per the IOMMU spec, the Destination, IsRun, and GATag fields are not cached * and thus don't require an invalidation to ensure the IOMMU consumes fresh * information. */ -int amd_iommu_update_ga(int cpu, bool is_run, void *data) +int amd_iommu_update_ga(int cpu, void *data) { struct amd_ir_data *ir_data = (struct amd_ir_data *)data; struct irte_ga *entry = (struct irte_ga *) ir_data->entry;
@@ -4015,8 +4017,10 @@ int amd_iommu_update_ga(int cpu, bool is_run, void *data) APICID_TO_IRTE_DEST_LO(cpu); entry->hi.fields.destination = APICID_TO_IRTE_DEST_HI(cpu); + entry->lo.fields_vapic.is_run = true; + } else { + entry->lo.fields_vapic.is_run = false; } - entry->lo.fields_vapic.is_run = is_run; return __modify_irte_ga(ir_data->iommu, ir_data->irq_2_irte.devid, ir_data->irq_2_irte.index, entry);
diff --git a/include/linux/amd-iommu.h b/include/linux/amd-iommu.h
index 99b4fa9a0296..fe0e16ffe0e5 100644
--- a/include/linux/amd-iommu.h
+++ b/include/linux/amd-iommu.h@@ -30,8 +30,7 @@ static inline void amd_iommu_detect(void) { } /* IOMMU AVIC Function */ extern int amd_iommu_register_ga_log_notifier(int (*notifier)(u32)); -extern int -amd_iommu_update_ga(int cpu, bool is_run, void *data); +extern int amd_iommu_update_ga(int cpu, void *data); extern int amd_iommu_activate_guest_mode(void *data); extern int amd_iommu_deactivate_guest_mode(void *data);
@@ -44,8 +43,7 @@ amd_iommu_register_ga_log_notifier(int (*notifier)(u32)) return 0; } -static inline int -amd_iommu_update_ga(int cpu, bool is_run, void *data) +static inline int amd_iommu_update_ga(int cpu, void *data) { return 0; }
--
2.50.0.rc1.591.g9c95f17f64-goog