From: Marc Zyngier maz@kernel.org
[ Upstream commit 5177fe91e4cf78a659aada2c9cf712db4d788481 ]
Userspace can specify which events a guest is allowed to use with the KVM_ARM_VCPU_PMU_V3_FILTER attribute. The list of allowed events can be identified by a guest from reading the PMCEID{0,1}_EL0 registers.
Changing the PMU event filter after a VCPU has run can cause reads of the registers performed before the filter is changed to return different values than reads performed with the new event filter in place. The architecture defines the two registers as read-only, and this behaviour contradicts that.
Keep track when the first VCPU has run and deny changes to the PMU event filter to prevent this from happening.
Signed-off-by: Marc Zyngier maz@kernel.org [ Alexandru E: Added commit message, updated ioctl documentation ] Signed-off-by: Alexandru Elisei alexandru.elisei@arm.com Signed-off-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20220127161759.53553-2-alexandru.elisei@arm.com Signed-off-by: Sasha Levin sashal@kernel.org --- Documentation/virt/kvm/devices/vcpu.rst | 2 +- arch/arm64/include/asm/kvm_host.h | 1 + arch/arm64/kvm/arm.c | 4 +++ arch/arm64/kvm/pmu-emul.c | 33 +++++++++++++++---------- 4 files changed, 26 insertions(+), 14 deletions(-)
diff --git a/Documentation/virt/kvm/devices/vcpu.rst b/Documentation/virt/kvm/devices/vcpu.rst index 60a29972d3f1..d063aaee5bb7 100644 --- a/Documentation/virt/kvm/devices/vcpu.rst +++ b/Documentation/virt/kvm/devices/vcpu.rst @@ -70,7 +70,7 @@ irqchip. -ENODEV PMUv3 not supported or GIC not initialized -ENXIO PMUv3 not properly configured or in-kernel irqchip not configured as required prior to calling this attribute - -EBUSY PMUv3 already initialized + -EBUSY PMUv3 already initialized or a VCPU has already run -EINVAL Invalid filter range ======= ======================================================
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 031e3a2537fc..8234626a945a 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -136,6 +136,7 @@ struct kvm_arch {
/* Memory Tagging Extension enabled for the guest */ bool mte_enabled; + bool ran_once; };
struct kvm_vcpu_fault_info { diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 4dca6ffd03d4..85a2a75f4498 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -634,6 +634,10 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu) if (kvm_vm_is_protected(kvm)) kvm_call_hyp_nvhe(__pkvm_vcpu_init_traps, vcpu);
+ mutex_lock(&kvm->lock); + kvm->arch.ran_once = true; + mutex_unlock(&kvm->lock); + return ret; }
diff --git a/arch/arm64/kvm/pmu-emul.c b/arch/arm64/kvm/pmu-emul.c index fbcfd4ec6f92..bc771bc1a041 100644 --- a/arch/arm64/kvm/pmu-emul.c +++ b/arch/arm64/kvm/pmu-emul.c @@ -924,6 +924,8 @@ static bool pmu_irq_is_valid(struct kvm *kvm, int irq)
int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) { + struct kvm *kvm = vcpu->kvm; + if (!kvm_vcpu_has_pmu(vcpu)) return -ENODEV;
@@ -941,7 +943,7 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) int __user *uaddr = (int __user *)(long)attr->addr; int irq;
- if (!irqchip_in_kernel(vcpu->kvm)) + if (!irqchip_in_kernel(kvm)) return -EINVAL;
if (get_user(irq, uaddr)) @@ -951,7 +953,7 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) if (!(irq_is_ppi(irq) || irq_is_spi(irq))) return -EINVAL;
- if (!pmu_irq_is_valid(vcpu->kvm, irq)) + if (!pmu_irq_is_valid(kvm, irq)) return -EINVAL;
if (kvm_arm_pmu_irq_initialized(vcpu)) @@ -966,7 +968,7 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) struct kvm_pmu_event_filter filter; int nr_events;
- nr_events = kvm_pmu_event_mask(vcpu->kvm) + 1; + nr_events = kvm_pmu_event_mask(kvm) + 1;
uaddr = (struct kvm_pmu_event_filter __user *)(long)attr->addr;
@@ -978,12 +980,17 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) filter.action != KVM_PMU_EVENT_DENY)) return -EINVAL;
- mutex_lock(&vcpu->kvm->lock); + mutex_lock(&kvm->lock); + + if (kvm->arch.ran_once) { + mutex_unlock(&kvm->lock); + return -EBUSY; + }
- if (!vcpu->kvm->arch.pmu_filter) { - vcpu->kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL_ACCOUNT); - if (!vcpu->kvm->arch.pmu_filter) { - mutex_unlock(&vcpu->kvm->lock); + if (!kvm->arch.pmu_filter) { + kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL_ACCOUNT); + if (!kvm->arch.pmu_filter) { + mutex_unlock(&kvm->lock); return -ENOMEM; }
@@ -994,17 +1001,17 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr) * events, the default is to allow. */ if (filter.action == KVM_PMU_EVENT_ALLOW) - bitmap_zero(vcpu->kvm->arch.pmu_filter, nr_events); + bitmap_zero(kvm->arch.pmu_filter, nr_events); else - bitmap_fill(vcpu->kvm->arch.pmu_filter, nr_events); + bitmap_fill(kvm->arch.pmu_filter, nr_events); }
if (filter.action == KVM_PMU_EVENT_ALLOW) - bitmap_set(vcpu->kvm->arch.pmu_filter, filter.base_event, filter.nevents); + bitmap_set(kvm->arch.pmu_filter, filter.base_event, filter.nevents); else - bitmap_clear(vcpu->kvm->arch.pmu_filter, filter.base_event, filter.nevents); + bitmap_clear(kvm->arch.pmu_filter, filter.base_event, filter.nevents);
- mutex_unlock(&vcpu->kvm->lock); + mutex_unlock(&kvm->lock);
return 0; }