On 05/23/2019 06:23 AM, Eric Hankland wrote:
- Add a VCPU ioctl that can control which events the guest can monitor.
Signed-off-by: ehankland <ehankland@xxxxxxxxxx>
---
Some events can provide a guest with information about other guests or the
host (e.g. L3 cache stats); providing the capability to restrict access
to a "safe" set of events would limit the potential for the PMU to be used
in any side channel attacks. This change introduces a new vcpu ioctl that
sets an event whitelist. If the guest attempts to program a counter for
any unwhitelisted event, the kernel counter won't be created, so any
RDPMC/RDMSR will show 0 instances of that event.
---
Documentation/virtual/kvm/api.txt | 16 +++++++++++
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/include/uapi/asm/kvm.h | 7 +++++
arch/x86/kvm/pmu.c | 44 +++++++++++++++++++++++++++++++
arch/x86/kvm/pmu.h | 3 +++
arch/x86/kvm/pmu_amd.c | 16 +++++++++++
arch/x86/kvm/vmx/pmu_intel.c | 16 +++++++++++
arch/x86/kvm/x86.c | 7 +++++
include/uapi/linux/kvm.h | 4 +++
9 files changed, 114 insertions(+)
diff --git a/Documentation/virtual/kvm/api.txt
b/Documentation/virtual/kvm/api.txt
index ba6c42c576dd..79cbe7339145 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -4065,6 +4065,22 @@ 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_WHITELIST
+
+Capability: KVM_CAP_PMU_WHITELIST
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_pmu_whitelist (in)
+Returns: 0 on success, -1 on error
+
+struct kvm_pmu_whitelist {
+ __u64 event_mask;
Is this "ARCH_PERFMON_EVENTSEL_EVENT | ARCH_PERFMON_EVENTSEL_UMASK"?
+ __u16 num_events;
+ __u64 events[0];
Can this be __u16?
The lower 16 bits (umask+eventsel) already determines what the event is.
+};
+This ioctl restricts the set of PMU events that the guest can program to the
+set of whitelisted events.
+
5. The kvm_run structure
------------------------
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 450d69a1e6fa..942647475999 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -477,6 +477,7 @@ struct kvm_pmu {
struct kvm_pmc fixed_counters[INTEL_PMC_MAX_FIXED];
struct irq_work irq_work;
u64 reprogram_pmi;
+ struct kvm_pmu_whitelist *whitelist;
This could be per-VM and under rcu?
};
struct kvm_pmu_ops;
diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
index 7a0e64ccd6ff..2633b48b75cd 100644
--- a/arch/x86/include/uapi/asm/kvm.h
+++ b/arch/x86/include/uapi/asm/kvm.h
@@ -421,4 +421,11 @@ struct kvm_nested_state {
__u8 data[0];
};
+/* for KVM_SET_PMU_WHITELIST */
+struct kvm_pmu_whitelist {
+ __u64 event_mask;
+ __u16 num_events;
+ __u64 events[0];
+};
+
#endif /* _ASM_X86_KVM_H */
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index e39741997893..d0d81cd3626d 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -101,6 +101,9 @@ static void pmc_reprogram_counter(struct kvm_pmc
*pmc, u32 type,
bool exclude_kernel, bool intr,
bool in_tx, bool in_tx_cp)
{
+ struct kvm_pmu *pmu = pmc_to_pmu(pmc);
+ int i;
+ u64 event_config;
struct perf_event *event;
struct perf_event_attr attr = {
.type = type,
@@ -127,6 +130,19 @@ static void pmc_reprogram_counter(struct kvm_pmc
*pmc, u32 type,
attr.config |= HSW_IN_TX_CHECKPOINTED;
}
+ if (pmu->whitelist) {
Why not moving this filter to reprogram_gp_counter?
You could directly compare "unit_mask, event_sel" with whitelist->events[i]
+ event_config = attr.config;
+ if (type == PERF_TYPE_HARDWARE)
+ event_config = kvm_x86_ops->pmu_ops->get_event_code(
+ attr.config);
+ event_config &= pmu->whitelist->event_mask;
+ for (i = 0; i < pmu->whitelist->num_events; i++)
+ if (event_config == pmu->whitelist->events[i])
+ break;
+ if (i == pmu->whitelist->num_events)
+ return;
+ }
+
event = perf_event_create_kernel_counter(&attr, -1, current,
intr ? kvm_perf_overflow_intr :
kvm_perf_overflow, pmc);
@@ -244,6 +260,34 @@ int kvm_pmu_is_valid_msr_idx(struct kvm_vcpu
*vcpu, unsigned idx)
return kvm_x86_ops->pmu_ops->is_valid_msr_idx(vcpu, idx);
}
+int kvm_vcpu_ioctl_set_pmu_whitelist(struct kvm_vcpu *vcpu,
+ struct kvm_pmu_whitelist __user *whtlst)
+{
+ struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+ struct kvm_pmu_whitelist *old = pmu->whitelist;
+ struct kvm_pmu_whitelist *new = NULL;
+ struct kvm_pmu_whitelist tmp;
+ int r;
+ size_t size;
+
+ r = -EFAULT;
+ if (copy_from_user(&tmp, whtlst, sizeof(struct kvm_pmu_whitelist)))
+ goto err;
I would directly return -EFAULT here.
+
+ size = sizeof(tmp) + sizeof(tmp.events[0]) * tmp.num_events;
+ new = kvzalloc(size, GFP_KERNEL_ACCOUNT);
+ r = -ENOMEM;
+ if (!new)
+ goto err;
Same here.
+ pmu->whitelist = new;
Forgot to copy the whitelist-ed events to new?
Best,
Wei
