* [PATCH V6 1/2] perf ignore LBR and extra_rsp
@ 2014-07-14 19:25 kan.liang
2014-07-14 19:25 ` [PATCH V6 2/2] kvm: ignore LBR and extra rsp kan.liang
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: kan.liang @ 2014-07-14 19:25 UTC (permalink / raw)
To: peterz; +Cc: andi, linux-kernel, kvm, Kan Liang
From: Kan Liang <kan.liang@intel.com>
x86, perf: Protect LBR and extra_regs against KVM lying
With -cpu host, KVM reports LBR and extra_regs support, if the host has
support.
When the guest perf driver tries to access LBR or extra_regs MSR,
it #GPs all MSR accesses,since KVM doesn't handle LBR and extra_regs support.
So check the related MSRs access right once at initialization time to avoid
the error access at runtime.
For reproducing the issue, please build the kernel with CONFIG_KVM_INTEL = y
(for host kernel).
And CONFIG_PARAVIRT = n and CONFIG_KVM_GUEST = n (for guest kernel).
Start the guest with -cpu host.
Run perf record with --branch-any or --branch-filter in guest to trigger LBR
Run perf stat offcore events (E.g. LLC-loads/LLC-load-misses ...) in guest to
trigger offcore_rsp #GP
Signed-off-by: Kan Liang <kan.liang@intel.com>
---
V2: Move the check code to initialization time.
V3: Add flag for each extra register.
Check all LBR MSRs at initialization time.
V4: Remove lbr_msr_access.
For LBR msr, simply set lbr_nr to 0 if check_msr failed.
Disable all extra msrs in creation places if check_msr failed.
V5: Fix check_msr broken
Don't check any more MSRs after the first fail
Return error when checking fail to stop creating the event
Remove the checking code path which never get
V6: Move extra_msr_access to struct extra_reg
Modify and move check_msr function to perf_event_intel.c
Other minor code changes
arch/x86/kernel/cpu/perf_event.c | 3 ++
arch/x86/kernel/cpu/perf_event.h | 20 ++++----
arch/x86/kernel/cpu/perf_event_intel.c | 66 ++++++++++++++++++++++++++-
arch/x86/kernel/cpu/perf_event_intel_uncore.h | 4 +-
4 files changed, 81 insertions(+), 12 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 2bdfbff..2879ecd 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -118,6 +118,9 @@ static int x86_pmu_extra_regs(u64 config, struct perf_event *event)
continue;
if (event->attr.config1 & ~er->valid_mask)
return -EINVAL;
+ /* Check if the extra msrs can be safely accessed*/
+ if (!er->extra_msr_access)
+ return -ENXIO;
reg->idx = er->idx;
reg->config = event->attr.config1;
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index 3b2f9bd..2e613b2 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -295,22 +295,24 @@ struct extra_reg {
u64 config_mask;
u64 valid_mask;
int idx; /* per_xxx->regs[] reg index */
+ bool extra_msr_access;
};
-#define EVENT_EXTRA_REG(e, ms, m, vm, i) { \
- .event = (e), \
- .msr = (ms), \
- .config_mask = (m), \
- .valid_mask = (vm), \
- .idx = EXTRA_REG_##i, \
+#define EVENT_EXTRA_REG(e, ms, m, vm, i, a) { \
+ .event = (e), \
+ .msr = (ms), \
+ .config_mask = (m), \
+ .valid_mask = (vm), \
+ .idx = EXTRA_REG_##i, \
+ .extra_msr_access = (a), \
}
#define INTEL_EVENT_EXTRA_REG(event, msr, vm, idx) \
- EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT, vm, idx)
+ EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT, vm, idx, true)
#define INTEL_UEVENT_EXTRA_REG(event, msr, vm, idx) \
EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT | \
- ARCH_PERFMON_EVENTSEL_UMASK, vm, idx)
+ ARCH_PERFMON_EVENTSEL_UMASK, vm, idx, true)
#define INTEL_UEVENT_PEBS_LDLAT_EXTRA_REG(c) \
INTEL_UEVENT_EXTRA_REG(c, \
@@ -318,7 +320,7 @@ struct extra_reg {
0xffff, \
LDLAT)
-#define EVENT_EXTRA_END EVENT_EXTRA_REG(0, 0, 0, 0, RSP_0)
+#define EVENT_EXTRA_END EVENT_EXTRA_REG(0, 0, 0, 0, RSP_0, false)
union perf_capabilities {
struct {
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index adb02aa..9c234d1 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2173,6 +2173,40 @@ static void intel_snb_check_microcode(void)
}
}
+/*
+ * Under certain circumstances, access certain MSR may cause #GP.
+ * The function tests if the input MSR can be safely accessed.
+ */
+static bool check_msr(unsigned long msr, u64 mask)
+{
+ u64 val_old, val_new, val_tmp;
+
+ /*
+ * Read the current value, change it and read it back to see if it
+ * matches, this is needed to detect certain hardware emulators
+ * (qemu/kvm) that don't trap on the MSR access and always return 0s.
+ */
+ if (rdmsrl_safe(msr, &val_old))
+ return false;
+ /*
+ * Only chagne the bits which can be updated by wrmsrl.
+ */
+ val_tmp = val_old ^ mask;
+ if (wrmsrl_safe(msr, val_tmp) ||
+ rdmsrl_safe(msr, &val_new))
+ return false;
+
+ if (val_new != val_tmp)
+ return false;
+
+ /* Here it's sure that the MSR can be safely accessed.
+ * Restore the old value and return.
+ */
+ wrmsrl(msr, val_old);
+
+ return true;
+}
+
static __init void intel_sandybridge_quirk(void)
{
x86_pmu.check_microcode = intel_snb_check_microcode;
@@ -2262,7 +2296,8 @@ __init int intel_pmu_init(void)
union cpuid10_ebx ebx;
struct event_constraint *c;
unsigned int unused;
- int version;
+ int version, i;
+ struct extra_reg *er;
if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
switch (boot_cpu_data.x86) {
@@ -2565,6 +2600,35 @@ __init int intel_pmu_init(void)
}
}
+ /*
+ * Access LBR MSR may cause #GP under certain circumstances.
+ * E.g. KVM doesn't support LBR MSR
+ * Check all LBT MSR here.
+ * Disable LBR access if any LBR MSRs can not be accessed.
+ */
+ if (x86_pmu.lbr_nr && !check_msr(x86_pmu.lbr_tos, 0x3UL))
+ x86_pmu.lbr_nr = 0;
+ for (i = 0; i < x86_pmu.lbr_nr; i++) {
+ if (!(check_msr(x86_pmu.lbr_from + i, 0xffffUL) &&
+ check_msr(x86_pmu.lbr_to + i, 0xffffUL)))
+ x86_pmu.lbr_nr = 0;
+ }
+ /*
+ * Access extra MSR may cause #GP under certain circumstances.
+ * E.g. KVM doesn't support offcore event
+ * Check all extra_regs here.
+ */
+ if (x86_pmu.extra_regs) {
+ for (er = x86_pmu.extra_regs; er->msr; er++) {
+ er->extra_msr_access =
+ check_msr(er->msr, 0x1ffUL);
+ /* Disable LBR select mapping */
+ if ((er->idx == EXTRA_REG_LBR) &&
+ !er->extra_msr_access)
+ x86_pmu.lbr_sel_map = NULL;
+ }
+ }
+
/* Support full width counters using alternative MSR range */
if (x86_pmu.intel_cap.full_width_write) {
x86_pmu.max_period = x86_pmu.cntval_mask;
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.h b/arch/x86/kernel/cpu/perf_event_intel_uncore.h
index 90236f0..d860e26 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.h
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.h
@@ -366,11 +366,11 @@
NHMEX_M_PMON_CTL_FLAG_MODE)
#define MBOX_INC_SEL_EXTAR_REG(c, r) \
EVENT_EXTRA_REG(MBOX_INC_SEL(c), NHMEX_M0_MSR_PMU_##r, \
- MBOX_INC_SEL_MASK, (u64)-1, NHMEX_M_##r)
+ MBOX_INC_SEL_MASK, (u64)-1, NHMEX_M_##r, true)
#define MBOX_SET_FLAG_SEL_EXTRA_REG(c, r) \
EVENT_EXTRA_REG(MBOX_SET_FLAG_SEL(c), NHMEX_M0_MSR_PMU_##r, \
MBOX_SET_FLAG_SEL_MASK, \
- (u64)-1, NHMEX_M_##r)
+ (u64)-1, NHMEX_M_##r, true)
/* NHM-EX Rbox */
#define NHMEX_R_MSR_GLOBAL_CTL 0xe00
--
1.8.3.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH V6 2/2] kvm: ignore LBR and extra rsp
2014-07-14 19:25 [PATCH V6 1/2] perf ignore LBR and extra_rsp kan.liang
@ 2014-07-14 19:25 ` kan.liang
2014-07-15 15:11 ` [PATCH V6 1/2] perf ignore LBR and extra_rsp Peter Zijlstra
2014-07-16 19:20 ` [tip:perf/urgent] perf/x86/intel: Protect LBR and extra_regs against KVM lying tip-bot for Kan Liang
2 siblings, 0 replies; 6+ messages in thread
From: kan.liang @ 2014-07-14 19:25 UTC (permalink / raw)
To: peterz; +Cc: andi, linux-kernel, kvm, Kan Liang, Andi Kleen
From: Kan Liang <kan.liang@intel.com>
With -cpu host KVM reports LBR and extra_regs support, so the perf driver may
accesses the LBR and extra_regs MSRs.
However, there is no LBR and extra_regs virtualization support yet. This could
causes guest to crash.
As a workaround, KVM just simply ignore the LBR and extra_regs MSRs to lie the
guest.
For reproducing the issue, please build the kernel with CONFIG_KVM_INTEL = y
(for host kernel).
And CONFIG_PARAVIRT = n and CONFIG_KVM_GUEST = n (for guest kernel).
Start the guest with -cpu host.
Run perf record with --branch-any or --branch-filter in guest to trigger LBR
Run perf stat offcore events (E.g. LLC-loads/LLC-load-misses ...) in guest to
trigger offcore_rsp #GP
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
---
V3: add MSR_LBR_TOS
V4: add MSR_LBR_SELECT and MSR_PEBS_LD_LAT_THRESHOLD
V5: set_msr should return 0 to lie the guest
arch/x86/kvm/pmu.c | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index cbecaa9..5fd5b44 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -331,6 +331,18 @@ bool kvm_pmu_msr(struct kvm_vcpu *vcpu, u32 msr)
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
ret = pmu->version > 1;
break;
+ case MSR_OFFCORE_RSP_0:
+ case MSR_OFFCORE_RSP_1:
+ case MSR_LBR_SELECT:
+ case MSR_PEBS_LD_LAT_THRESHOLD:
+ case MSR_LBR_TOS:
+ /* At most 8-deep LBR for core and atom */
+ case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 7:
+ case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 7:
+ /* 16-deep LBR for core i3/i5/i7 series processors */
+ case MSR_LBR_NHM_FROM ... MSR_LBR_NHM_FROM + 15:
+ case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 15:
+ return 1; /* to avoid crashes */
default:
ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)
|| get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0)
@@ -358,6 +370,19 @@ int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, u32 index, u64 *data)
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
*data = pmu->global_ovf_ctrl;
return 0;
+ case MSR_OFFCORE_RSP_0:
+ case MSR_OFFCORE_RSP_1:
+ case MSR_LBR_SELECT:
+ case MSR_PEBS_LD_LAT_THRESHOLD:
+ case MSR_LBR_TOS:
+ /* At most 8-deep LBR for core and atom */
+ case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 7:
+ case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 7:
+ /* 16-deep LBR for core i3/i5/i7 series processors */
+ case MSR_LBR_NHM_FROM ... MSR_LBR_NHM_FROM + 15:
+ case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 15:
+ *data = 0;
+ return 0;
default:
if ((pmc = get_gp_pmc(pmu, index, MSR_IA32_PERFCTR0)) ||
(pmc = get_fixed_pmc(pmu, index))) {
@@ -409,6 +434,19 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 0;
}
break;
+ case MSR_OFFCORE_RSP_0:
+ case MSR_OFFCORE_RSP_1:
+ case MSR_LBR_SELECT:
+ case MSR_PEBS_LD_LAT_THRESHOLD:
+ case MSR_LBR_TOS:
+ /* At most 8-deep LBR for core and atom */
+ case MSR_LBR_CORE_FROM ... MSR_LBR_CORE_FROM + 7:
+ case MSR_LBR_CORE_TO ... MSR_LBR_CORE_TO + 7:
+ /* 16-deep LBR for core i3/i5/i7 series processors */
+ case MSR_LBR_NHM_FROM ... MSR_LBR_NHM_FROM + 15:
+ case MSR_LBR_NHM_TO ... MSR_LBR_NHM_TO + 15:
+ /* dummy for now */
+ return 0;
default:
if ((pmc = get_gp_pmc(pmu, index, MSR_IA32_PERFCTR0)) ||
(pmc = get_fixed_pmc(pmu, index))) {
--
1.8.3.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH V6 1/2] perf ignore LBR and extra_rsp
2014-07-14 19:25 [PATCH V6 1/2] perf ignore LBR and extra_rsp kan.liang
2014-07-14 19:25 ` [PATCH V6 2/2] kvm: ignore LBR and extra rsp kan.liang
@ 2014-07-15 15:11 ` Peter Zijlstra
2014-07-15 15:32 ` Liang, Kan
2014-07-16 19:20 ` [tip:perf/urgent] perf/x86/intel: Protect LBR and extra_regs against KVM lying tip-bot for Kan Liang
2 siblings, 1 reply; 6+ messages in thread
From: Peter Zijlstra @ 2014-07-15 15:11 UTC (permalink / raw)
To: kan.liang; +Cc: andi, linux-kernel, kvm
[-- Attachment #1: Type: text/plain, Size: 7134 bytes --]
On Mon, Jul 14, 2014 at 12:25:56PM -0700, kan.liang@intel.com wrote:
Close enough.
> +#define EVENT_EXTRA_REG(e, ms, m, vm, i, a) { \
> + .event = (e), \
> + .msr = (ms), \
> + .config_mask = (m), \
> + .valid_mask = (vm), \
> + .idx = EXTRA_REG_##i, \
> + .extra_msr_access = (a), \
> }
>
> #define INTEL_EVENT_EXTRA_REG(event, msr, vm, idx) \
> - EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT, vm, idx)
> + EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT, vm, idx, true)
>
> #define INTEL_UEVENT_EXTRA_REG(event, msr, vm, idx) \
> EVENT_EXTRA_REG(event, msr, ARCH_PERFMON_EVENTSEL_EVENT | \
> - ARCH_PERFMON_EVENTSEL_UMASK, vm, idx)
> + ARCH_PERFMON_EVENTSEL_UMASK, vm, idx, true)
>
> #define INTEL_UEVENT_PEBS_LDLAT_EXTRA_REG(c) \
> INTEL_UEVENT_EXTRA_REG(c, \
> @@ -318,7 +320,7 @@ struct extra_reg {
> 0xffff, \
> LDLAT)
>
> -#define EVENT_EXTRA_END EVENT_EXTRA_REG(0, 0, 0, 0, RSP_0)
> +#define EVENT_EXTRA_END EVENT_EXTRA_REG(0, 0, 0, 0, RSP_0, false)
> diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.h b/arch/x86/kernel/cpu/perf_event_intel_uncore.h
> index 90236f0..d860e26 100644
> --- a/arch/x86/kernel/cpu/perf_event_intel_uncore.h
> +++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.h
> @@ -366,11 +366,11 @@
> NHMEX_M_PMON_CTL_FLAG_MODE)
> #define MBOX_INC_SEL_EXTAR_REG(c, r) \
> EVENT_EXTRA_REG(MBOX_INC_SEL(c), NHMEX_M0_MSR_PMU_##r, \
> - MBOX_INC_SEL_MASK, (u64)-1, NHMEX_M_##r)
> + MBOX_INC_SEL_MASK, (u64)-1, NHMEX_M_##r, true)
> #define MBOX_SET_FLAG_SEL_EXTRA_REG(c, r) \
> EVENT_EXTRA_REG(MBOX_SET_FLAG_SEL(c), NHMEX_M0_MSR_PMU_##r, \
> MBOX_SET_FLAG_SEL_MASK, \
> - (u64)-1, NHMEX_M_##r)
> + (u64)-1, NHMEX_M_##r, true)
>
> /* NHM-EX Rbox */
> #define NHMEX_R_MSR_GLOBAL_CTL 0xe00
Since nobody ever treats EVENT_EXTRA_END as an actual event, the value
of .extra_msr_access is irrelevant, this leaves the only 'possible'
value 'true' and we can delete all those changes.
Which, combined with a few whitespace cleanups, gives the below patch.
---
Subject: x86, perf: Protect LBR and extra_regs against KVM lying
From: Kan Liang <kan.liang@intel.com>
Date: Mon, 14 Jul 2014 12:25:56 -0700
With -cpu host, KVM reports LBR and extra_regs support, if the host has
support.
When the guest perf driver tries to access LBR or extra_regs MSR,
it #GPs all MSR accesses,since KVM doesn't handle LBR and extra_regs support.
So check the related MSRs access right once at initialization time to avoid
the error access at runtime.
For reproducing the issue, please build the kernel with CONFIG_KVM_INTEL = y
(for host kernel).
And CONFIG_PARAVIRT = n and CONFIG_KVM_GUEST = n (for guest kernel).
Start the guest with -cpu host.
Run perf record with --branch-any or --branch-filter in guest to trigger LBR
Run perf stat offcore events (E.g. LLC-loads/LLC-load-misses ...) in guest to
trigger offcore_rsp #GP
Cc: andi@firstfloor.org
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1405365957-20202-1-git-send-email-kan.liang@intel.com
---
arch/x86/kernel/cpu/perf_event.c | 3 +
arch/x86/kernel/cpu/perf_event.h | 12 +++---
arch/x86/kernel/cpu/perf_event_intel.c | 66 ++++++++++++++++++++++++++++++++-
3 files changed, 75 insertions(+), 6 deletions(-)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -118,6 +118,9 @@ static int x86_pmu_extra_regs(u64 config
continue;
if (event->attr.config1 & ~er->valid_mask)
return -EINVAL;
+ /* Check if the extra msrs can be safely accessed*/
+ if (!er->extra_msr_access)
+ return -ENXIO;
reg->idx = er->idx;
reg->config = event->attr.config1;
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -295,14 +295,16 @@ struct extra_reg {
u64 config_mask;
u64 valid_mask;
int idx; /* per_xxx->regs[] reg index */
+ bool extra_msr_access;
};
#define EVENT_EXTRA_REG(e, ms, m, vm, i) { \
- .event = (e), \
- .msr = (ms), \
- .config_mask = (m), \
- .valid_mask = (vm), \
- .idx = EXTRA_REG_##i, \
+ .event = (e), \
+ .msr = (ms), \
+ .config_mask = (m), \
+ .valid_mask = (vm), \
+ .idx = EXTRA_REG_##i, \
+ .extra_msr_access = true, \
}
#define INTEL_EVENT_EXTRA_REG(event, msr, vm, idx) \
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2182,6 +2182,41 @@ static void intel_snb_check_microcode(vo
}
}
+/*
+ * Under certain circumstances, access certain MSR may cause #GP.
+ * The function tests if the input MSR can be safely accessed.
+ */
+static bool check_msr(unsigned long msr, u64 mask)
+{
+ u64 val_old, val_new, val_tmp;
+
+ /*
+ * Read the current value, change it and read it back to see if it
+ * matches, this is needed to detect certain hardware emulators
+ * (qemu/kvm) that don't trap on the MSR access and always return 0s.
+ */
+ if (rdmsrl_safe(msr, &val_old))
+ return false;
+
+ /*
+ * Only change the bits which can be updated by wrmsrl.
+ */
+ val_tmp = val_old ^ mask;
+ if (wrmsrl_safe(msr, val_tmp) ||
+ rdmsrl_safe(msr, &val_new))
+ return false;
+
+ if (val_new != val_tmp)
+ return false;
+
+ /* Here it's sure that the MSR can be safely accessed.
+ * Restore the old value and return.
+ */
+ wrmsrl(msr, val_old);
+
+ return true;
+}
+
static __init void intel_sandybridge_quirk(void)
{
x86_pmu.check_microcode = intel_snb_check_microcode;
@@ -2271,7 +2306,8 @@ __init int intel_pmu_init(void)
union cpuid10_ebx ebx;
struct event_constraint *c;
unsigned int unused;
- int version;
+ struct extra_reg *er;
+ int version, i;
if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
switch (boot_cpu_data.x86) {
@@ -2577,6 +2613,34 @@ __init int intel_pmu_init(void)
}
}
+ /*
+ * Access LBR MSR may cause #GP under certain circumstances.
+ * E.g. KVM doesn't support LBR MSR
+ * Check all LBT MSR here.
+ * Disable LBR access if any LBR MSRs can not be accessed.
+ */
+ if (x86_pmu.lbr_nr && !check_msr(x86_pmu.lbr_tos, 0x3UL))
+ x86_pmu.lbr_nr = 0;
+ for (i = 0; i < x86_pmu.lbr_nr; i++) {
+ if (!(check_msr(x86_pmu.lbr_from + i, 0xffffUL) &&
+ check_msr(x86_pmu.lbr_to + i, 0xffffUL)))
+ x86_pmu.lbr_nr = 0;
+ }
+
+ /*
+ * Access extra MSR may cause #GP under certain circumstances.
+ * E.g. KVM doesn't support offcore event
+ * Check all extra_regs here.
+ */
+ if (x86_pmu.extra_regs) {
+ for (er = x86_pmu.extra_regs; er->msr; er++) {
+ er->extra_msr_access = check_msr(er->msr, 0x1ffUL);
+ /* Disable LBR select mapping */
+ if ((er->idx == EXTRA_REG_LBR) && !er->extra_msr_access)
+ x86_pmu.lbr_sel_map = NULL;
+ }
+ }
+
/* Support full width counters using alternative MSR range */
if (x86_pmu.intel_cap.full_width_write) {
x86_pmu.max_period = x86_pmu.cntval_mask;
[-- Attachment #2: Type: application/pgp-signature, Size: 836 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
* RE: [PATCH V6 1/2] perf ignore LBR and extra_rsp
2014-07-15 15:11 ` [PATCH V6 1/2] perf ignore LBR and extra_rsp Peter Zijlstra
@ 2014-07-15 15:32 ` Liang, Kan
2014-07-15 16:16 ` Peter Zijlstra
0 siblings, 1 reply; 6+ messages in thread
From: Liang, Kan @ 2014-07-15 15:32 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: andi, linux-kernel, kvm
>
>
> Since nobody ever treats EVENT_EXTRA_END as an actual event, the value
> of .extra_msr_access is irrelevant, this leaves the only 'possible'
> value 'true' and we can delete all those changes.
>
Right.
> Which, combined with a few whitespace cleanups, gives the below patch.
Thanks. Your change is perfect. Do I need to resubmit the patch to the mailing list?
Thanks,
Kan
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH V6 1/2] perf ignore LBR and extra_rsp
2014-07-15 15:32 ` Liang, Kan
@ 2014-07-15 16:16 ` Peter Zijlstra
0 siblings, 0 replies; 6+ messages in thread
From: Peter Zijlstra @ 2014-07-15 16:16 UTC (permalink / raw)
To: Liang, Kan; +Cc: andi, linux-kernel, kvm
[-- Attachment #1: Type: text/plain, Size: 493 bytes --]
On Tue, Jul 15, 2014 at 03:32:36PM +0000, Liang, Kan wrote:
>
>
> >
> >
> > Since nobody ever treats EVENT_EXTRA_END as an actual event, the value
> > of .extra_msr_access is irrelevant, this leaves the only 'possible'
> > value 'true' and we can delete all those changes.
> >
> Right.
> > Which, combined with a few whitespace cleanups, gives the below patch.
>
> Thanks. Your change is perfect. Do I need to resubmit the patch to the mailing list?
Nope, got it queued.
[-- Attachment #2: Type: application/pgp-signature, Size: 836 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread
* [tip:perf/urgent] perf/x86/intel: Protect LBR and extra_regs against KVM lying
2014-07-14 19:25 [PATCH V6 1/2] perf ignore LBR and extra_rsp kan.liang
2014-07-14 19:25 ` [PATCH V6 2/2] kvm: ignore LBR and extra rsp kan.liang
2014-07-15 15:11 ` [PATCH V6 1/2] perf ignore LBR and extra_rsp Peter Zijlstra
@ 2014-07-16 19:20 ` tip-bot for Kan Liang
2 siblings, 0 replies; 6+ messages in thread
From: tip-bot for Kan Liang @ 2014-07-16 19:20 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, eranian, paulus, hpa, mingo, torvalds, peterz,
maria.n.dimakopoulou, acme, kan.liang, zheng.z.yan, ak, junk,
tglx
Commit-ID: 338b522ca43cfd32d11a370f4203bcd089c6c877
Gitweb: http://git.kernel.org/tip/338b522ca43cfd32d11a370f4203bcd089c6c877
Author: Kan Liang <kan.liang@intel.com>
AuthorDate: Mon, 14 Jul 2014 12:25:56 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 16 Jul 2014 13:18:43 +0200
perf/x86/intel: Protect LBR and extra_regs against KVM lying
With -cpu host, KVM reports LBR and extra_regs support, if the host has
support.
When the guest perf driver tries to access LBR or extra_regs MSR,
it #GPs all MSR accesses,since KVM doesn't handle LBR and extra_regs support.
So check the related MSRs access right once at initialization time to avoid
the error access at runtime.
For reproducing the issue, please build the kernel with CONFIG_KVM_INTEL = y
(for host kernel).
And CONFIG_PARAVIRT = n and CONFIG_KVM_GUEST = n (for guest kernel).
Start the guest with -cpu host.
Run perf record with --branch-any or --branch-filter in guest to trigger LBR
Run perf stat offcore events (E.g. LLC-loads/LLC-load-misses ...) in guest to
trigger offcore_rsp #GP
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Maria Dimakopoulou <maria.n.dimakopoulou@gmail.com>
Cc: Mark Davies <junk@eslaf.co.uk>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Yan, Zheng <zheng.z.yan@intel.com>
Link: http://lkml.kernel.org/r/1405365957-20202-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/cpu/perf_event.c | 3 ++
arch/x86/kernel/cpu/perf_event.h | 12 ++++---
arch/x86/kernel/cpu/perf_event_intel.c | 66 +++++++++++++++++++++++++++++++++-
3 files changed, 75 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 2bdfbff..2879ecd 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -118,6 +118,9 @@ static int x86_pmu_extra_regs(u64 config, struct perf_event *event)
continue;
if (event->attr.config1 & ~er->valid_mask)
return -EINVAL;
+ /* Check if the extra msrs can be safely accessed*/
+ if (!er->extra_msr_access)
+ return -ENXIO;
reg->idx = er->idx;
reg->config = event->attr.config1;
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index 3b2f9bd..8ade931 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -295,14 +295,16 @@ struct extra_reg {
u64 config_mask;
u64 valid_mask;
int idx; /* per_xxx->regs[] reg index */
+ bool extra_msr_access;
};
#define EVENT_EXTRA_REG(e, ms, m, vm, i) { \
- .event = (e), \
- .msr = (ms), \
- .config_mask = (m), \
- .valid_mask = (vm), \
- .idx = EXTRA_REG_##i, \
+ .event = (e), \
+ .msr = (ms), \
+ .config_mask = (m), \
+ .valid_mask = (vm), \
+ .idx = EXTRA_REG_##i, \
+ .extra_msr_access = true, \
}
#define INTEL_EVENT_EXTRA_REG(event, msr, vm, idx) \
diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index c206815..2502d0d 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -2182,6 +2182,41 @@ static void intel_snb_check_microcode(void)
}
}
+/*
+ * Under certain circumstances, access certain MSR may cause #GP.
+ * The function tests if the input MSR can be safely accessed.
+ */
+static bool check_msr(unsigned long msr, u64 mask)
+{
+ u64 val_old, val_new, val_tmp;
+
+ /*
+ * Read the current value, change it and read it back to see if it
+ * matches, this is needed to detect certain hardware emulators
+ * (qemu/kvm) that don't trap on the MSR access and always return 0s.
+ */
+ if (rdmsrl_safe(msr, &val_old))
+ return false;
+
+ /*
+ * Only change the bits which can be updated by wrmsrl.
+ */
+ val_tmp = val_old ^ mask;
+ if (wrmsrl_safe(msr, val_tmp) ||
+ rdmsrl_safe(msr, &val_new))
+ return false;
+
+ if (val_new != val_tmp)
+ return false;
+
+ /* Here it's sure that the MSR can be safely accessed.
+ * Restore the old value and return.
+ */
+ wrmsrl(msr, val_old);
+
+ return true;
+}
+
static __init void intel_sandybridge_quirk(void)
{
x86_pmu.check_microcode = intel_snb_check_microcode;
@@ -2271,7 +2306,8 @@ __init int intel_pmu_init(void)
union cpuid10_ebx ebx;
struct event_constraint *c;
unsigned int unused;
- int version;
+ struct extra_reg *er;
+ int version, i;
if (!cpu_has(&boot_cpu_data, X86_FEATURE_ARCH_PERFMON)) {
switch (boot_cpu_data.x86) {
@@ -2577,6 +2613,34 @@ __init int intel_pmu_init(void)
}
}
+ /*
+ * Access LBR MSR may cause #GP under certain circumstances.
+ * E.g. KVM doesn't support LBR MSR
+ * Check all LBT MSR here.
+ * Disable LBR access if any LBR MSRs can not be accessed.
+ */
+ if (x86_pmu.lbr_nr && !check_msr(x86_pmu.lbr_tos, 0x3UL))
+ x86_pmu.lbr_nr = 0;
+ for (i = 0; i < x86_pmu.lbr_nr; i++) {
+ if (!(check_msr(x86_pmu.lbr_from + i, 0xffffUL) &&
+ check_msr(x86_pmu.lbr_to + i, 0xffffUL)))
+ x86_pmu.lbr_nr = 0;
+ }
+
+ /*
+ * Access extra MSR may cause #GP under certain circumstances.
+ * E.g. KVM doesn't support offcore event
+ * Check all extra_regs here.
+ */
+ if (x86_pmu.extra_regs) {
+ for (er = x86_pmu.extra_regs; er->msr; er++) {
+ er->extra_msr_access = check_msr(er->msr, 0x1ffUL);
+ /* Disable LBR select mapping */
+ if ((er->idx == EXTRA_REG_LBR) && !er->extra_msr_access)
+ x86_pmu.lbr_sel_map = NULL;
+ }
+ }
+
/* Support full width counters using alternative MSR range */
if (x86_pmu.intel_cap.full_width_write) {
x86_pmu.max_period = x86_pmu.cntval_mask;
^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2014-07-16 19:21 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2014-07-14 19:25 [PATCH V6 1/2] perf ignore LBR and extra_rsp kan.liang
2014-07-14 19:25 ` [PATCH V6 2/2] kvm: ignore LBR and extra rsp kan.liang
2014-07-15 15:11 ` [PATCH V6 1/2] perf ignore LBR and extra_rsp Peter Zijlstra
2014-07-15 15:32 ` Liang, Kan
2014-07-15 16:16 ` Peter Zijlstra
2014-07-16 19:20 ` [tip:perf/urgent] perf/x86/intel: Protect LBR and extra_regs against KVM lying tip-bot for Kan Liang
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