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KVM: arm64: Do not change the PMU event filter after a VCPU has run

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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
This commit is contained in:
Marc Zyngier 2022-01-27 16:17:54 +00:00
parent dfd42facf1
commit 5177fe91e4
4 changed files with 26 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
Documentation/virt/kvm/devices/vcpu.rst
View File

@ -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
======= ======================================================

1
arch/arm64/include/asm/kvm_host.h
View File

@ -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 {

4
arch/arm64/kvm/arm.c
View File

@ -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;
}

33
arch/arm64/kvm/pmu-emul.c
View File

@ -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 (!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.ran_once) {
mutex_unlock(&kvm->lock);
return -EBUSY;
}
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;
}