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KVM: arm64: Add PMU event filtering infrastructure

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It can be desirable to expose a PMU to a guest, and yet not want the
guest to be able to count some of the implemented events (because this
would give information on shared resources, for example.

For this, let's extend the PMUv3 device API, and offer a way to setup a
bitmap of the allowed events (the default being no bitmap, and thus no
filtering).

Userspace can thus allow/deny ranges of event. The default policy
depends on the "polarity" of the first filter setup (default deny if the
filter allows events, and default allow if the filter denies events).
This allows to setup exactly what is allowed for a given guest.

Note that although the ioctl is per-vcpu, the map of allowed events is
global to the VM (it can be setup from any vcpu until the vcpu PMU is
initialized).

Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier 2020-02-12 11:31:02 +00:00
parent fd65a3b5f8
commit d7eec2360e
4 changed files with 86 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
arch/arm64/include/asm/kvm_host.h
View File

@ -111,6 +111,11 @@ struct kvm_arch {
*/
bool return_nisv_io_abort_to_user;
/*
* VM-wide PMU filter, implemented as a bitmap and big enough for
* up to 2^10 events (ARMv8.0) or 2^16 events (ARMv8.1+).
*/
unsigned long *pmu_filter;
unsigned int pmuver;
};

16
arch/arm64/include/uapi/asm/kvm.h
View File

@ -159,6 +159,21 @@ struct kvm_sync_regs {
struct kvm_arch_memory_slot {
};
/*
* PMU filter structure. Describe a range of events with a particular
* action. To be used with KVM_ARM_VCPU_PMU_V3_FILTER.
*/
struct kvm_pmu_event_filter {
__u16 base_event;
__u16 nevents;
#define KVM_PMU_EVENT_ALLOW 0
#define KVM_PMU_EVENT_DENY 1
__u8 action;
__u8 pad[3];
};
/* for KVM_GET/SET_VCPU_EVENTS */
struct kvm_vcpu_events {
struct {
@ -329,6 +344,7 @@ struct kvm_vcpu_events {
#define KVM_ARM_VCPU_PMU_V3_CTRL 0
#define KVM_ARM_VCPU_PMU_V3_IRQ 0
#define KVM_ARM_VCPU_PMU_V3_INIT 1
#define KVM_ARM_VCPU_PMU_V3_FILTER 2
#define KVM_ARM_VCPU_TIMER_CTRL 1
#define KVM_ARM_VCPU_TIMER_IRQ_VTIMER 0
#define KVM_ARM_VCPU_TIMER_IRQ_PTIMER 1

2
arch/arm64/kvm/arm.c
View File

@ -145,6 +145,8 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
{
int i;
bitmap_free(kvm->arch.pmu_filter);
kvm_vgic_destroy(kvm);
for (i = 0; i < KVM_MAX_VCPUS; ++i) {

69
arch/arm64/kvm/pmu-emul.c
View File

@ -593,11 +593,21 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx)
data = __vcpu_sys_reg(vcpu, reg);
kvm_pmu_stop_counter(vcpu, pmc);
eventsel = data & kvm_pmu_event_mask(vcpu->kvm);;
if (pmc->idx == ARMV8_PMU_CYCLE_IDX)
eventsel = ARMV8_PMUV3_PERFCTR_CPU_CYCLES;
else
eventsel = data & kvm_pmu_event_mask(vcpu->kvm);
/* Software increment event does't need to be backed by a perf event */
if (eventsel == ARMV8_PMUV3_PERFCTR_SW_INCR &&
pmc->idx != ARMV8_PMU_CYCLE_IDX)
/* Software increment event doesn't need to be backed by a perf event */
if (eventsel == ARMV8_PMUV3_PERFCTR_SW_INCR)
return;
/*
* If we have a filter in place and that the event isn't allowed, do
* not install a perf event either.
*/
if (vcpu->kvm->arch.pmu_filter &&
!test_bit(eventsel, vcpu->kvm->arch.pmu_filter))
return;
memset(&attr, 0, sizeof(struct perf_event_attr));
@ -609,8 +619,7 @@ static void kvm_pmu_create_perf_event(struct kvm_vcpu *vcpu, u64 select_idx)
attr.exclude_kernel = data & ARMV8_PMU_EXCLUDE_EL1 ? 1 : 0;
attr.exclude_hv = 1; /* Don't count EL2 events */
attr.exclude_host = 1; /* Don't count host events */
attr.config = (pmc->idx == ARMV8_PMU_CYCLE_IDX) ?
ARMV8_PMUV3_PERFCTR_CPU_CYCLES : eventsel;
attr.config = eventsel;
counter = kvm_pmu_get_pair_counter_value(vcpu, pmc);
@ -889,6 +898,53 @@ int kvm_arm_pmu_v3_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
vcpu->arch.pmu.irq_num = irq;
return 0;
}
case KVM_ARM_VCPU_PMU_V3_FILTER: {
struct kvm_pmu_event_filter __user *uaddr;
struct kvm_pmu_event_filter filter;
int nr_events;
nr_events = kvm_pmu_event_mask(vcpu->kvm) + 1;
uaddr = (struct kvm_pmu_event_filter __user *)(long)attr->addr;
if (copy_from_user(&filter, uaddr, sizeof(filter)))
return -EFAULT;
if (((u32)filter.base_event + filter.nevents) > nr_events ||
(filter.action != KVM_PMU_EVENT_ALLOW &&
filter.action != KVM_PMU_EVENT_DENY))
return -EINVAL;
mutex_lock(&vcpu->kvm->lock);
if (!vcpu->kvm->arch.pmu_filter) {
vcpu->kvm->arch.pmu_filter = bitmap_alloc(nr_events, GFP_KERNEL);
if (!vcpu->kvm->arch.pmu_filter) {
mutex_unlock(&vcpu->kvm->lock);
return -ENOMEM;
}
/*
* The default depends on the first applied filter.
* If it allows events, the default is to deny.
* Conversely, if the first filter denies a set of
* events, the default is to allow.
*/
if (filter.action == KVM_PMU_EVENT_ALLOW)
bitmap_zero(vcpu->kvm->arch.pmu_filter, nr_events);
else
bitmap_fill(vcpu->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);
else
bitmap_clear(vcpu->kvm->arch.pmu_filter, filter.base_event, filter.nevents);
mutex_unlock(&vcpu->kvm->lock);
return 0;
}
case KVM_ARM_VCPU_PMU_V3_INIT:
return kvm_arm_pmu_v3_init(vcpu);
}
@ -925,6 +981,7 @@ int kvm_arm_pmu_v3_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr)
switch (attr->attr) {
case KVM_ARM_VCPU_PMU_V3_IRQ:
case KVM_ARM_VCPU_PMU_V3_INIT:
case KVM_ARM_VCPU_PMU_V3_FILTER:
if (kvm_arm_support_pmu_v3() &&
test_bit(KVM_ARM_VCPU_PMU_V3, vcpu->arch.features))
return 0;