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Subject[PATCH v2] KVM: x86: PMU Event Filter
- Add a VM ioctl that can control which events the guest can monitor.

Signed-off-by: ehankland <ehankland@google.com>
---
Changes since v1:
-Moved to a vm ioctl rather than a vcpu one
-Changed from a whitelist to a configurable filter which can either be
white or black
-Only restrict GP counters since fixed counters require extra handling
and they can be disabled by setting the guest cpuid (though only by
setting the number - they can't be disabled individually)
---
Documentation/virtual/kvm/api.txt | 25 +++++++++++++
arch/x86/include/asm/kvm_host.h | 2 +
arch/x86/include/uapi/asm/kvm.h | 10 +++++
arch/x86/kvm/pmu.c | 61 +++++++++++++++++++++++++++++++
arch/x86/kvm/pmu.h | 1 +
arch/x86/kvm/x86.c | 6 +++
include/uapi/linux/kvm.h | 3 ++
7 files changed, 108 insertions(+)

diff --git a/Documentation/virtual/kvm/api.txt
b/Documentation/virtual/kvm/api.txt
index 91fd86fcc49f..a9ee8da36595 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4065,6 +4065,31 @@ KVM_ARM_VCPU_FINALIZE call.
See KVM_ARM_VCPU_INIT for details of vcpu features that require finalization
using this ioctl.

+4.120 KVM_SET_PMU_EVENT_FILTER
+
+Capability: KVM_CAP_PMU_EVENT_FILTER
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_pmu_event_filter (in)
+Returns: 0 on success, -1 on error
+
+struct kvm_pmu_event_filter {
+ __u32 type;
+ __u32 nevents;
+ __u64 events[0];
+};
+
+This ioctl restricts the set of PMU events that the guest can program to either
+a whitelist or a blacklist of events. The eventsel+umask of each event the
+guest attempts to program is compared against the events field to determine
+whether the guest should have access. This only affects general purpose
+counters; fixed purpose counters can be disabled by changing the perfmon
+CPUID leaf.
+
+Valid values for 'type':
+#define KVM_PMU_EVENT_WHITELIST 0
+#define KVM_PMU_EVENT_BLACKLIST 1
+

5. The kvm_run structure
------------------------
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index f46a12a5cf2e..34d017bd1d1b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -933,6 +933,8 @@ struct kvm_arch {

bool guest_can_read_msr_platform_info;
bool exception_payload_enabled;
+
+ struct kvm_pmu_event_filter *pmu_event_filter;
};

struct kvm_vm_stat {
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index f9b021e16ebc..4d2e905b7d79 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -422,4 +422,14 @@ struct kvm_nested_state {
__u8 data[0];
};

+/* for KVM_CAP_PMU_EVENT_FILTER */
+struct kvm_pmu_event_filter {
+ __u32 type;
+ __u32 nevents;
+ __u64 events[0];
+};
+
+#define KVM_PMU_EVENT_WHITELIST 0
+#define KVM_PMU_EVENT_BLACKLIST 1
+
#endif /* _ASM_X86_KVM_H */
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index dd745b58ffd8..d674b79ff8da 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -22,6 +22,9 @@
#include "lapic.h"
#include "pmu.h"

+/* This keeps the total size of the filter under 4k. */
+#define KVM_PMU_EVENT_FILTER_MAX_EVENTS 63
+
/* NOTE:
* - Each perf counter is defined as "struct kvm_pmc";
* - There are two types of perf counters: general purpose (gp) and fixed.
@@ -144,6 +147,10 @@ void reprogram_gp_counter(struct kvm_pmc *pmc,
u64 eventsel)
{
unsigned config, type = PERF_TYPE_RAW;
u8 event_select, unit_mask;
+ struct kvm_arch *arch = &pmc->vcpu->kvm->arch;
+ struct kvm_pmu_event_filter *filter;
+ int i;
+ bool allow_event = true;

if (eventsel & ARCH_PERFMON_EVENTSEL_PIN_CONTROL)
printk_once("kvm pmu: pin control bit is ignored\n");
@@ -155,6 +162,24 @@ void reprogram_gp_counter(struct kvm_pmc *pmc,
u64 eventsel)
if (!(eventsel & ARCH_PERFMON_EVENTSEL_ENABLE) || !pmc_is_enabled(pmc))
return;

+ rcu_read_lock();
+ filter = rcu_dereference(arch->pmu_event_filter);
+ if (filter) {
+ for (i = 0; i < filter->nevents; i++)
+ if (filter->events[i] ==
+ (eventsel & AMD64_RAW_EVENT_MASK_NB))
+ break;
+ if (filter->type == KVM_PMU_EVENT_WHITELIST &&
+ i == filter->nevents)
+ allow_event = false;
+ if (filter->type == KVM_PMU_EVENT_BLACKLIST &&
+ i < filter->nevents)
+ allow_event = false;
+ }
+ rcu_read_unlock();
+ if (!allow_event)
+ return;
+
event_select = eventsel & ARCH_PERFMON_EVENTSEL_EVENT;
unit_mask = (eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;

@@ -351,3 +376,39 @@ void kvm_pmu_destroy(struct kvm_vcpu *vcpu)
{
kvm_pmu_reset(vcpu);
}
+
+int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp)
+{
+ struct kvm_pmu_event_filter tmp, *filter;
+ size_t size;
+ int r;
+
+ if (copy_from_user(&tmp, argp, sizeof(tmp)))
+ return -EFAULT;
+
+ if (tmp.nevents > KVM_PMU_EVENT_FILTER_MAX_EVENTS)
+ return -E2BIG;
+
+ size = sizeof(tmp) + sizeof(tmp.events[0]) * tmp.nevents;
+ filter = vmalloc(size);
+ if (!filter)
+ return -ENOMEM;
+
+ r = -EFAULT;
+ if (copy_from_user(filter, argp, size))
+ goto cleanup;
+
+ /* Ensure nevents can't be changed between the user copies. */
+ *filter = tmp;
+
+ mutex_lock(&kvm->lock);
+ rcu_swap_protected(kvm->arch.pmu_event_filter, filter,
+ mutex_is_locked(&kvm->lock));
+ mutex_unlock(&kvm->lock);
+
+ synchronize_rcu();
+ r = 0;
+cleanup:
+ kvfree(filter);
+ return r;
+}
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 22dff661145a..58265f761c3b 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -118,6 +118,7 @@ void kvm_pmu_refresh(struct kvm_vcpu *vcpu);
void kvm_pmu_reset(struct kvm_vcpu *vcpu);
void kvm_pmu_init(struct kvm_vcpu *vcpu);
void kvm_pmu_destroy(struct kvm_vcpu *vcpu);
+int kvm_vm_ioctl_set_pmu_event_filter(struct kvm *kvm, void __user *argp);

bool is_vmware_backdoor_pmc(u32 pmc_idx);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2e302e977dac..9ddfc7193bc6 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3135,6 +3135,7 @@ int kvm_vm_ioctl_check_extension(struct kvm
*kvm, long ext)
case KVM_CAP_GET_MSR_FEATURES:
case KVM_CAP_MSR_PLATFORM_INFO:
case KVM_CAP_EXCEPTION_PAYLOAD:
+ case KVM_CAP_PMU_EVENT_FILTER:
r = 1;
break;
case KVM_CAP_SYNC_REGS:
@@ -4978,6 +4979,11 @@ long kvm_arch_vm_ioctl(struct file *filp,
r = kvm_vm_ioctl_hv_eventfd(kvm, &hvevfd);
break;
}
+ case KVM_SET_PMU_EVENT_FILTER: {
+ r = kvm_vm_ioctl_set_pmu_event_filter(kvm, argp);
+ break;
+
+ }
default:
r = -ENOTTY;
}
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index c2152f3dd02d..b18ff80e356a 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -995,6 +995,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_ARM_SVE 170
#define KVM_CAP_ARM_PTRAUTH_ADDRESS 171
#define KVM_CAP_ARM_PTRAUTH_GENERIC 172
+#define KVM_CAP_PMU_EVENT_FILTER 173

#ifdef KVM_CAP_IRQ_ROUTING

@@ -1329,6 +1330,8 @@ struct kvm_s390_ucas_mapping {
#define KVM_PPC_GET_RMMU_INFO _IOW(KVMIO, 0xb0, struct kvm_ppc_rmmu_info)
/* Available with KVM_CAP_PPC_GET_CPU_CHAR */
#define KVM_PPC_GET_CPU_CHAR _IOR(KVMIO, 0xb1, struct kvm_ppc_cpu_char)
+/* Availabile with KVM_CAP_PMU_EVENT_FILTER */
+#define KVM_SET_PMU_EVENT_FILTER _IOW(KVMIO, 0xb2, struct
kvm_pmu_event_filter)

/* ioctl for vm fd */
#define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device)
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