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Subject[PATCH V6 2/5] perf/x86/kvm: Avoid unnecessary work in guest filtering
Date
From: Andi Kleen <ak@linux.intel.com>

KVM added a workaround for PEBS events leaking into guests with
commit 26a4f3c08de4 ("perf/x86: disable PEBS on a guest entry.")
This uses the VT entry/exit list to add an extra disable of the
PEBS_ENABLE MSR.

Intel also added a fix for this issue to microcode updates on
Haswell/Broadwell/Skylake.

It turns out using the MSR entry/exit list makes VM exits
significantly slower. The list is only needed for disabling
PEBS, because the GLOBAL_CTRL change gets optimized by
KVM into changing the VMCS.

Check for the microcode updates that have the microcode
fix for leaking PEBS, and disable the extra entry/exit list
entry for PEBS_ENABLE. In addition we always clear the
GLOBAL_CTRL for the PEBS counter while running in the guest,
which is enough to make them never fire at the wrong
side of the host/guest transition.

The overhead for VM exits with the filtering active with the patch is
reduced from 8% to 4%.

The microcode patch has already been merged into future platforms.
This patch is one-off thing. The quirks is used here.

For other old platforms which doesn't have microcode patch and quirks,
extra disable of the PEBS_ENABLE MSR is still required.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---

Changes since V5:
- The microcode patch has already been merged into future platforms.
So this patch is actually one-off things. The quirks is still used in
the patch.
Rename pebs_isolated to pebs_no_isolation. The default value is 0. So
we don't need to worry about the future platforms. However, we have to
set pebs_no_isolation = 1 for other old platforms which doesn't have
microcode patch and quirks.
Also update the commit message accordingly.
- Remove "We" in commit messages
- Add my SOB
- Align isolation_ucodes vertically
- Remove intel_check_isolation() from SNB check.

arch/x86/events/intel/core.c | 85 ++++++++++++++++++++++++++++++++++++++------
arch/x86/events/perf_event.h | 15 ++++----
2 files changed, 83 insertions(+), 17 deletions(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 40e12cf..13baff5 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -18,6 +18,7 @@
#include <asm/hardirq.h>
#include <asm/intel-family.h>
#include <asm/apic.h>
+#include <asm/cpu_device_id.h>

#include "../perf_event.h"

@@ -3206,16 +3207,27 @@ static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr)
arr[0].msr = MSR_CORE_PERF_GLOBAL_CTRL;
arr[0].host = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_guest_mask;
arr[0].guest = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_host_mask;
- /*
- * If PMU counter has PEBS enabled it is not enough to disable counter
- * on a guest entry since PEBS memory write can overshoot guest entry
- * and corrupt guest memory. Disabling PEBS solves the problem.
- */
- arr[1].msr = MSR_IA32_PEBS_ENABLE;
- arr[1].host = cpuc->pebs_enabled;
- arr[1].guest = 0;
+ if (x86_pmu.flags & PMU_FL_PEBS_ALL)
+ arr[0].guest &= ~cpuc->pebs_enabled;
+ else
+ arr[0].guest &= ~(cpuc->pebs_enabled & PEBS_COUNTER_MASK);
+ *nr = 1;
+
+ if (x86_pmu.pebs_no_isolation) {
+ /*
+ * If PMU counter has PEBS enabled it is not enough to
+ * disable counter on a guest entry since PEBS memory
+ * write can overshoot guest entry and corrupt guest
+ * memory. Disabling PEBS solves the problem.
+ *
+ * Don't do this if the CPU already enforces it.
+ */
+ arr[1].msr = MSR_IA32_PEBS_ENABLE;
+ arr[1].host = cpuc->pebs_enabled;
+ arr[1].guest = 0;
+ *nr = 2;
+ }

- *nr = 2;
return arr;
}

@@ -3733,6 +3745,41 @@ static __init void intel_clovertown_quirk(void)
x86_pmu.pebs_constraints = NULL;
}

+static const struct x86_cpu_desc isolation_ucodes[] = {
+ INTEL_CPU_DESC(INTEL_FAM6_HASWELL_CORE, 3, 0x0000001f),
+ INTEL_CPU_DESC(INTEL_FAM6_HASWELL_ULT, 1, 0x0000001e),
+ INTEL_CPU_DESC(INTEL_FAM6_HASWELL_GT3E, 1, 0x00000015),
+ INTEL_CPU_DESC(INTEL_FAM6_HASWELL_X, 2, 0x00000037),
+ INTEL_CPU_DESC(INTEL_FAM6_HASWELL_X, 4, 0x0000000a),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_CORE, 4, 0x00000023),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_GT3E, 1, 0x00000014),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D, 2, 0x00000010),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D, 3, 0x07000009),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D, 4, 0x0f000009),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D, 5, 0x0e000002),
+ INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_X, 2, 0x0b000014),
+ INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 3, 0x00000021),
+ INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X, 4, 0x00000000),
+ INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_MOBILE, 3, 0x0000007c),
+ INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_DESKTOP, 3, 0x0000007c),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP, 9, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE, 9, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE, 10, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE, 11, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE, 12, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP, 10, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP, 11, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP, 12, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP, 13, 0x0000004e),
+ INTEL_CPU_DESC(INTEL_FAM6_CANNONLAKE_MOBILE, 3, 0x00000000),
+ {}
+};
+
+static void intel_check_isolation(void)
+{
+ x86_pmu.pebs_no_isolation = !x86_cpu_has_min_microcode_rev(isolation_ucodes);
+}
+
static int intel_snb_pebs_broken(int cpu)
{
u32 rev = UINT_MAX; /* default to broken for unknown models */
@@ -3838,6 +3885,12 @@ static __init void intel_sandybridge_quirk(void)
cpus_read_unlock();
}

+static __init void intel_isolation_quirk(void)
+{
+ x86_pmu.check_microcode = intel_check_isolation;
+ intel_check_isolation();
+}
+
static const struct { int id; char *name; } intel_arch_events_map[] __initconst = {
{ PERF_COUNT_HW_CPU_CYCLES, "cpu cycles" },
{ PERF_COUNT_HW_INSTRUCTIONS, "instructions" },
@@ -4178,6 +4231,7 @@ __init int intel_pmu_init(void)

x86_pmu.event_constraints = intel_core2_event_constraints;
x86_pmu.pebs_constraints = intel_core2_pebs_event_constraints;
+ x86_pmu.pebs_no_isolation = 1;
pr_cont("Core2 events, ");
name = "core2";
break;
@@ -4209,6 +4263,7 @@ __init int intel_pmu_init(void)
intel_pmu_pebs_data_source_nhm();
x86_add_quirk(intel_nehalem_quirk);
x86_pmu.pebs_no_tlb = 1;
+ x86_pmu.pebs_no_isolation = 1;
extra_attr = nhm_format_attr;

pr_cont("Nehalem events, ");
@@ -4228,6 +4283,7 @@ __init int intel_pmu_init(void)
x86_pmu.event_constraints = intel_gen_event_constraints;
x86_pmu.pebs_constraints = intel_atom_pebs_event_constraints;
x86_pmu.pebs_aliases = intel_pebs_aliases_core2;
+ x86_pmu.pebs_no_isolation = 1;
pr_cont("Atom events, ");
name = "bonnell";
break;
@@ -4249,6 +4305,7 @@ __init int intel_pmu_init(void)
x86_pmu.extra_regs = intel_slm_extra_regs;
x86_pmu.flags |= PMU_FL_HAS_RSP_1;
x86_pmu.cpu_events = slm_events_attrs;
+ x86_pmu.pebs_no_isolation = 1;
extra_attr = slm_format_attr;
pr_cont("Silvermont events, ");
name = "silvermont";
@@ -4276,6 +4333,7 @@ __init int intel_pmu_init(void)
x86_pmu.lbr_pt_coexist = true;
x86_pmu.flags |= PMU_FL_HAS_RSP_1;
x86_pmu.cpu_events = glm_events_attrs;
+ x86_pmu.pebs_no_isolation = 1;
extra_attr = slm_format_attr;
pr_cont("Goldmont events, ");
name = "goldmont";
@@ -4303,6 +4361,7 @@ __init int intel_pmu_init(void)
x86_pmu.flags |= PMU_FL_PEBS_ALL;
x86_pmu.get_event_constraints = glp_get_event_constraints;
x86_pmu.cpu_events = glm_events_attrs;
+ x86_pmu.pebs_no_isolation = 1;
/* Goldmont Plus has 4-wide pipeline */
event_attr_td_total_slots_scale_glm.event_str = "4";
extra_attr = slm_format_attr;
@@ -4336,6 +4395,7 @@ __init int intel_pmu_init(void)
X86_CONFIG(.event=0xb1, .umask=0x3f, .inv=1, .cmask=1);

intel_pmu_pebs_data_source_nhm();
+ x86_pmu.pebs_no_isolation = 1;
extra_attr = nhm_format_attr;
pr_cont("Westmere events, ");
name = "westmere";
@@ -4366,6 +4426,7 @@ __init int intel_pmu_init(void)
x86_pmu.flags |= PMU_FL_NO_HT_SHARING;

x86_pmu.cpu_events = snb_events_attrs;
+ x86_pmu.pebs_no_isolation = 1;
mem_attr = snb_mem_events_attrs;

/* UOPS_ISSUED.ANY,c=1,i=1 to count stall cycles */
@@ -4405,7 +4466,7 @@ __init int intel_pmu_init(void)
/* all extra regs are per-cpu when HT is on */
x86_pmu.flags |= PMU_FL_HAS_RSP_1;
x86_pmu.flags |= PMU_FL_NO_HT_SHARING;
-
+ x86_pmu.pebs_no_isolation = 1;
x86_pmu.cpu_events = snb_events_attrs;
mem_attr = snb_mem_events_attrs;

@@ -4424,6 +4485,7 @@ __init int intel_pmu_init(void)
case INTEL_FAM6_HASWELL_X:
case INTEL_FAM6_HASWELL_ULT:
case INTEL_FAM6_HASWELL_GT3E:
+ x86_add_quirk(intel_isolation_quirk);
x86_add_quirk(intel_ht_bug);
x86_pmu.late_ack = true;
memcpy(hw_cache_event_ids, hsw_hw_cache_event_ids, sizeof(hw_cache_event_ids));
@@ -4456,6 +4518,7 @@ __init int intel_pmu_init(void)
case INTEL_FAM6_BROADWELL_XEON_D:
case INTEL_FAM6_BROADWELL_GT3E:
case INTEL_FAM6_BROADWELL_X:
+ x86_add_quirk(intel_isolation_quirk);
x86_pmu.late_ack = true;
memcpy(hw_cache_event_ids, hsw_hw_cache_event_ids, sizeof(hw_cache_event_ids));
memcpy(hw_cache_extra_regs, hsw_hw_cache_extra_regs, sizeof(hw_cache_extra_regs));
@@ -4508,6 +4571,7 @@ __init int intel_pmu_init(void)
/* all extra regs are per-cpu when HT is on */
x86_pmu.flags |= PMU_FL_HAS_RSP_1;
x86_pmu.flags |= PMU_FL_NO_HT_SHARING;
+ x86_pmu.pebs_no_isolation = 1;
extra_attr = slm_format_attr;
pr_cont("Knights Landing/Mill events, ");
name = "knights-landing";
@@ -4518,6 +4582,7 @@ __init int intel_pmu_init(void)
case INTEL_FAM6_SKYLAKE_X:
case INTEL_FAM6_KABYLAKE_MOBILE:
case INTEL_FAM6_KABYLAKE_DESKTOP:
+ x86_add_quirk(intel_isolation_quirk);
x86_pmu.late_ack = true;
memcpy(hw_cache_event_ids, skl_hw_cache_event_ids, sizeof(hw_cache_event_ids));
memcpy(hw_cache_extra_regs, skl_hw_cache_extra_regs, sizeof(hw_cache_extra_regs));
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index 78d7b70..dea716e 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -601,13 +601,14 @@ struct x86_pmu {
/*
* Intel DebugStore bits
*/
- unsigned int bts :1,
- bts_active :1,
- pebs :1,
- pebs_active :1,
- pebs_broken :1,
- pebs_prec_dist :1,
- pebs_no_tlb :1;
+ unsigned int bts :1,
+ bts_active :1,
+ pebs :1,
+ pebs_active :1,
+ pebs_broken :1,
+ pebs_prec_dist :1,
+ pebs_no_tlb :1,
+ pebs_no_isolation :1;
int pebs_record_size;
int pebs_buffer_size;
void (*drain_pebs)(struct pt_regs *regs);
--
2.7.4
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