[tip:perf/core] perf/x86/amd/uncore: Set ThreadMask and SliceMask for L3 Cache perf events

[tip:perf/core] perf/x86/amd/uncore: Set ThreadMask and SliceMask for L3 Cache perf events

[tip-bot for Natarajan, Janakarajan]

Commit-ID:  d7cbbe49a9304520181fb8c9272d1327deec8453
Gitweb:     https://git.kernel.org/tip/d7cbbe49a9304520181fb8c9272d1327deec8453
Author:     Natarajan, Janakarajan <Janakarajan.Natarajan@amd.com>
AuthorDate: Thu, 27 Sep 2018 15:51:55 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 2 Oct 2018 09:38:04 +0200

perf/x86/amd/uncore: Set ThreadMask and SliceMask for L3 Cache perf events

In Family 17h, some L3 Cache Performance events require the ThreadMask
and SliceMask to be set. For other events, these fields do not affect
the count either way.

Set ThreadMask and SliceMask to 0xFF and 0xF respectively.

Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Suravee <Suravee.Suthikulpanit@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/Message-ID:
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/amd/uncore.c      | 10 ++++++++++
 arch/x86/include/asm/perf_event.h |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
index 981ba5e8241b..8671de126eac 100644
--- a/arch/x86/events/amd/uncore.c
+++ b/arch/x86/events/amd/uncore.c
@@ -36,6 +36,7 @@
 
 static int num_counters_llc;
 static int num_counters_nb;
+static bool l3_mask;
 
 static HLIST_HEAD(uncore_unused_list);
 
@@ -209,6 +210,13 @@ static int amd_uncore_event_init(struct perf_event *event)
 	hwc->config = event->attr.config & AMD64_RAW_EVENT_MASK_NB;
 	hwc->idx = -1;
 
+	/*
+	 * SliceMask and ThreadMask need to be set for certain L3 events in
+	 * Family 17h. For other events, the two fields do not affect the count.
+	 */
+	if (l3_mask)
+		hwc->config |= (AMD64_L3_SLICE_MASK | AMD64_L3_THREAD_MASK);
+
 	if (event->cpu < 0)
 		return -EINVAL;
 
@@ -525,6 +533,7 @@ static int __init amd_uncore_init(void)
 		amd_llc_pmu.name	  = "amd_l3";
 		format_attr_event_df.show = &event_show_df;
 		format_attr_event_l3.show = &event_show_l3;
+		l3_mask			  = true;
 	} else {
 		num_counters_nb		  = NUM_COUNTERS_NB;
 		num_counters_llc	  = NUM_COUNTERS_L2;
@@ -532,6 +541,7 @@ static int __init amd_uncore_init(void)
 		amd_llc_pmu.name	  = "amd_l2";
 		format_attr_event_df	  = format_attr_event;
 		format_attr_event_l3	  = format_attr_event;
+		l3_mask			  = false;
 	}
 
 	amd_nb_pmu.attr_groups	= amd_uncore_attr_groups_df;
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 12f54082f4c8..78241b736f2a 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -46,6 +46,14 @@
 #define INTEL_ARCH_EVENT_MASK	\
 	(ARCH_PERFMON_EVENTSEL_UMASK | ARCH_PERFMON_EVENTSEL_EVENT)
 
+#define AMD64_L3_SLICE_SHIFT				48
+#define AMD64_L3_SLICE_MASK				\
+	((0xFULL) << AMD64_L3_SLICE_SHIFT)
+
+#define AMD64_L3_THREAD_SHIFT				56
+#define AMD64_L3_THREAD_MASK				\
+	((0xFFULL) << AMD64_L3_THREAD_SHIFT)
+
 #define X86_RAW_EVENT_MASK		\
 	(ARCH_PERFMON_EVENTSEL_EVENT |	\
 	 ARCH_PERFMON_EVENTSEL_UMASK |	\

[tip:perf/urgent] x86/perf/amd: Resolve race condition when disabling PMC

[tip-bot for Lendacky, Thomas]

Commit-ID:  914123fa39042e651d79eaf86bbf63a1b938dddf
Gitweb:     https://git.kernel.org/tip/914123fa39042e651d79eaf86bbf63a1b938dddf
Author:     Lendacky, Thomas <Thomas.Lendacky@amd.com>
AuthorDate: Tue, 2 Apr 2019 15:21:14 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Apr 2019 11:40:32 +0200

x86/perf/amd: Resolve race condition when disabling PMC

On AMD processors, the detection of an overflowed counter in the NMI
handler relies on the current value of the counter. So, for example, to
check for overflow on a 48 bit counter, bit 47 is checked to see if it
is 1 (not overflowed) or 0 (overflowed).

There is currently a race condition present when disabling and then
updating the PMC. Increased NMI latency in newer AMD processors makes this
race condition more pronounced. If the counter value has overflowed, it is
possible to update the PMC value before the NMI handler can run. The
updated PMC value is not an overflowed value, so when the perf NMI handler
does run, it will not find an overflowed counter. This may appear as an
unknown NMI resulting in either a panic or a series of messages, depending
on how the kernel is configured.

To eliminate this race condition, the PMC value must be checked after
disabling the counter. Add an AMD function, amd_pmu_disable_all(), that
will wait for the NMI handler to reset any active and overflowed counter
after calling x86_pmu_disable_all().

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # 4.14.x-
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lkml.kernel.org/r/Message-ID:
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/amd/core.c | 65 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 62 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 7d2d7c801dba..c09ee88b0eed 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -3,6 +3,7 @@
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/delay.h>
 #include <asm/apicdef.h>
 
 #include "../perf_event.h"
@@ -429,6 +430,64 @@ static void amd_pmu_cpu_dead(int cpu)
 	}
 }
 
+/*
+ * When a PMC counter overflows, an NMI is used to process the event and
+ * reset the counter. NMI latency can result in the counter being updated
+ * before the NMI can run, which can result in what appear to be spurious
+ * NMIs. This function is intended to wait for the NMI to run and reset
+ * the counter to avoid possible unhandled NMI messages.
+ */
+#define OVERFLOW_WAIT_COUNT	50
+
+static void amd_pmu_wait_on_overflow(int idx)
+{
+	unsigned int i;
+	u64 counter;
+
+	/*
+	 * Wait for the counter to be reset if it has overflowed. This loop
+	 * should exit very, very quickly, but just in case, don't wait
+	 * forever...
+	 */
+	for (i = 0; i < OVERFLOW_WAIT_COUNT; i++) {
+		rdmsrl(x86_pmu_event_addr(idx), counter);
+		if (counter & (1ULL << (x86_pmu.cntval_bits - 1)))
+			break;
+
+		/* Might be in IRQ context, so can't sleep */
+		udelay(1);
+	}
+}
+
+static void amd_pmu_disable_all(void)
+{
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	int idx;
+
+	x86_pmu_disable_all();
+
+	/*
+	 * This shouldn't be called from NMI context, but add a safeguard here
+	 * to return, since if we're in NMI context we can't wait for an NMI
+	 * to reset an overflowed counter value.
+	 */
+	if (in_nmi())
+		return;
+
+	/*
+	 * Check each counter for overflow and wait for it to be reset by the
+	 * NMI if it has overflowed. This relies on the fact that all active
+	 * counters are always enabled when this function is caled and
+	 * ARCH_PERFMON_EVENTSEL_INT is always set.
+	 */
+	for (idx = 0; idx < x86_pmu.num_counters; idx++) {
+		if (!test_bit(idx, cpuc->active_mask))
+			continue;
+
+		amd_pmu_wait_on_overflow(idx);
+	}
+}
+
 static struct event_constraint *
 amd_get_event_constraints(struct cpu_hw_events *cpuc, int idx,
 			  struct perf_event *event)
@@ -622,7 +681,7 @@ static ssize_t amd_event_sysfs_show(char *page, u64 config)
 static __initconst const struct x86_pmu amd_pmu = {
 	.name			= "AMD",
 	.handle_irq		= x86_pmu_handle_irq,
-	.disable_all		= x86_pmu_disable_all,
+	.disable_all		= amd_pmu_disable_all,
 	.enable_all		= x86_pmu_enable_all,
 	.enable			= x86_pmu_enable_event,
 	.disable		= x86_pmu_disable_event,
@@ -732,7 +791,7 @@ void amd_pmu_enable_virt(void)
 	cpuc->perf_ctr_virt_mask = 0;
 
 	/* Reload all events */
-	x86_pmu_disable_all();
+	amd_pmu_disable_all();
 	x86_pmu_enable_all(0);
 }
 EXPORT_SYMBOL_GPL(amd_pmu_enable_virt);
@@ -750,7 +809,7 @@ void amd_pmu_disable_virt(void)
 	cpuc->perf_ctr_virt_mask = AMD64_EVENTSEL_HOSTONLY;
 
 	/* Reload all events */
-	x86_pmu_disable_all();
+	amd_pmu_disable_all();
 	x86_pmu_enable_all(0);
 }
 EXPORT_SYMBOL_GPL(amd_pmu_disable_virt);

[tip:perf/urgent] x86/perf/amd: Resolve NMI latency issues for active PMCs

[tip-bot for Lendacky, Thomas]

Commit-ID:  6d3edaae16c6c7d238360f2841212c2b26774d5e
Gitweb:     https://git.kernel.org/tip/6d3edaae16c6c7d238360f2841212c2b26774d5e
Author:     Lendacky, Thomas <Thomas.Lendacky@amd.com>
AuthorDate: Tue, 2 Apr 2019 15:21:16 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Apr 2019 11:40:32 +0200

x86/perf/amd: Resolve NMI latency issues for active PMCs

On AMD processors, the detection of an overflowed PMC counter in the NMI
handler relies on the current value of the PMC. So, for example, to check
for overflow on a 48-bit counter, bit 47 is checked to see if it is 1 (not
overflowed) or 0 (overflowed).

When the perf NMI handler executes it does not know in advance which PMC
counters have overflowed. As such, the NMI handler will process all active
PMC counters that have overflowed. NMI latency in newer AMD processors can
result in multiple overflowed PMC counters being processed in one NMI and
then a subsequent NMI, that does not appear to be a back-to-back NMI, not
finding any PMC counters that have overflowed. This may appear to be an
unhandled NMI resulting in either a panic or a series of messages,
depending on how the kernel was configured.

To mitigate this issue, add an AMD handle_irq callback function,
amd_pmu_handle_irq(), that will invoke the common x86_pmu_handle_irq()
function and upon return perform some additional processing that will
indicate if the NMI has been handled or would have been handled had an
earlier NMI not handled the overflowed PMC. Using a per-CPU variable, a
minimum value of the number of active PMCs or 2 will be set whenever a
PMC is active. This is used to indicate the possible number of NMIs that
can still occur. The value of 2 is used for when an NMI does not arrive
at the LAPIC in time to be collapsed into an already pending NMI. Each
time the function is called without having handled an overflowed counter,
the per-CPU value is checked. If the value is non-zero, it is decremented
and the NMI indicates that it handled the NMI. If the value is zero, then
the NMI indicates that it did not handle the NMI.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # 4.14.x-
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lkml.kernel.org/r/Message-ID:
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/amd/core.c | 56 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index c09ee88b0eed..34c191453ce3 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -4,10 +4,13 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
+#include <linux/nmi.h>
 #include <asm/apicdef.h>
 
 #include "../perf_event.h"
 
+static DEFINE_PER_CPU(unsigned int, perf_nmi_counter);
+
 static __initconst const u64 amd_hw_cache_event_ids
 				[PERF_COUNT_HW_CACHE_MAX]
 				[PERF_COUNT_HW_CACHE_OP_MAX]
@@ -488,6 +491,57 @@ static void amd_pmu_disable_all(void)
 	}
 }
 
+/*
+ * Because of NMI latency, if multiple PMC counters are active or other sources
+ * of NMIs are received, the perf NMI handler can handle one or more overflowed
+ * PMC counters outside of the NMI associated with the PMC overflow. If the NMI
+ * doesn't arrive at the LAPIC in time to become a pending NMI, then the kernel
+ * back-to-back NMI support won't be active. This PMC handler needs to take into
+ * account that this can occur, otherwise this could result in unknown NMI
+ * messages being issued. Examples of this is PMC overflow while in the NMI
+ * handler when multiple PMCs are active or PMC overflow while handling some
+ * other source of an NMI.
+ *
+ * Attempt to mitigate this by using the number of active PMCs to determine
+ * whether to return NMI_HANDLED if the perf NMI handler did not handle/reset
+ * any PMCs. The per-CPU perf_nmi_counter variable is set to a minimum of the
+ * number of active PMCs or 2. The value of 2 is used in case an NMI does not
+ * arrive at the LAPIC in time to be collapsed into an already pending NMI.
+ */
+static int amd_pmu_handle_irq(struct pt_regs *regs)
+{
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+	int active, handled;
+
+	/*
+	 * Obtain the active count before calling x86_pmu_handle_irq() since
+	 * it is possible that x86_pmu_handle_irq() may make a counter
+	 * inactive (through x86_pmu_stop).
+	 */
+	active = __bitmap_weight(cpuc->active_mask, X86_PMC_IDX_MAX);
+
+	/* Process any counter overflows */
+	handled = x86_pmu_handle_irq(regs);
+
+	/*
+	 * If a counter was handled, record the number of possible remaining
+	 * NMIs that can occur.
+	 */
+	if (handled) {
+		this_cpu_write(perf_nmi_counter,
+			       min_t(unsigned int, 2, active));
+
+		return handled;
+	}
+
+	if (!this_cpu_read(perf_nmi_counter))
+		return NMI_DONE;
+
+	this_cpu_dec(perf_nmi_counter);
+
+	return NMI_HANDLED;
+}
+
 static struct event_constraint *
 amd_get_event_constraints(struct cpu_hw_events *cpuc, int idx,
 			  struct perf_event *event)
@@ -680,7 +734,7 @@ static ssize_t amd_event_sysfs_show(char *page, u64 config)
 
 static __initconst const struct x86_pmu amd_pmu = {
 	.name			= "AMD",
-	.handle_irq		= x86_pmu_handle_irq,
+	.handle_irq		= amd_pmu_handle_irq,
 	.disable_all		= amd_pmu_disable_all,
 	.enable_all		= x86_pmu_enable_all,
 	.enable			= x86_pmu_enable_event,

[tip:perf/urgent] x86/perf/amd: Remove need to check "running" bit in NMI handler

[tip-bot for Lendacky, Thomas]

Commit-ID:  60f52ab61c7dc0a991125903ae06a35d1812698c
Gitweb:     https://git.kernel.org/tip/60f52ab61c7dc0a991125903ae06a35d1812698c
Author:     Lendacky, Thomas <Thomas.Lendacky@amd.com>
AuthorDate: Tue, 2 Apr 2019 15:21:18 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 3 Apr 2019 11:40:32 +0200

x86/perf/amd: Remove need to check "running" bit in NMI handler

Spurious interrupt support was adding to perf in:
commit 63e6be6d98e1 ("perf, x86: Catch spurious interrupts after disabling counters")

The two previous patches (resolving the race condition when disabling a
PMC and NMI latency mitigation) allow for the removal of this older
spurious interrupt support.

Currently in x86_pmu_stop(), the bit for the PMC in the active_mask bitmap
is cleared before disabling the PMC, which sets up a race condition. This
race condition was mitigated by introducing the running bitmap. That race
condition can be eliminated by first disabling the PMC, waiting for PMC
reset on overflow and then clearing the bit for the PMC in the active_mask
bitmap. The NMI handler will not re-enable a disabled counter.

If x86_pmu_stop() is called from the perf NMI handler, the NMI latency
mitigation support will guard against any unhandled NMI messages.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # 4.14.x-
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lkml.kernel.org/r/Message-ID:
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/amd/core.c | 19 ++++++++++++++++++-
 arch/x86/events/core.c     | 13 +++----------
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 34c191453ce3..5d423653f744 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -491,6 +491,23 @@ static void amd_pmu_disable_all(void)
 	}
 }
 
+static void amd_pmu_disable_event(struct perf_event *event)
+{
+	x86_pmu_disable_event(event);
+
+	/*
+	 * This can be called from NMI context (via x86_pmu_stop). The counter
+	 * may have overflowed, but either way, we'll never see it get reset
+	 * by the NMI if we're already in the NMI. And the NMI latency support
+	 * below will take care of any pending NMI that might have been
+	 * generated by the overflow.
+	 */
+	if (in_nmi())
+		return;
+
+	amd_pmu_wait_on_overflow(event->hw.idx);
+}
+
 /*
  * Because of NMI latency, if multiple PMC counters are active or other sources
  * of NMIs are received, the perf NMI handler can handle one or more overflowed
@@ -738,7 +755,7 @@ static __initconst const struct x86_pmu amd_pmu = {
 	.disable_all		= amd_pmu_disable_all,
 	.enable_all		= x86_pmu_enable_all,
 	.enable			= x86_pmu_enable_event,
-	.disable		= x86_pmu_disable_event,
+	.disable		= amd_pmu_disable_event,
 	.hw_config		= amd_pmu_hw_config,
 	.schedule_events	= x86_schedule_events,
 	.eventsel		= MSR_K7_EVNTSEL0,
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index e2b1447192a8..81911e11a15d 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1349,8 +1349,9 @@ void x86_pmu_stop(struct perf_event *event, int flags)
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct hw_perf_event *hwc = &event->hw;
 
-	if (__test_and_clear_bit(hwc->idx, cpuc->active_mask)) {
+	if (test_bit(hwc->idx, cpuc->active_mask)) {
 		x86_pmu.disable(event);
+		__clear_bit(hwc->idx, cpuc->active_mask);
 		cpuc->events[hwc->idx] = NULL;
 		WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
 		hwc->state |= PERF_HES_STOPPED;
@@ -1447,16 +1448,8 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
 	apic_write(APIC_LVTPC, APIC_DM_NMI);
 
 	for (idx = 0; idx < x86_pmu.num_counters; idx++) {
-		if (!test_bit(idx, cpuc->active_mask)) {
-			/*
-			 * Though we deactivated the counter some cpus
-			 * might still deliver spurious interrupts still
-			 * in flight. Catch them:
-			 */
-			if (__test_and_clear_bit(idx, cpuc->running))
-				handled++;
+		if (!test_bit(idx, cpuc->active_mask))
 			continue;
-		}
 
 		event = cpuc->events[idx];
 

[tip:perf/urgent] x86/perf/amd: Remove need to check "running" bit in NMI handler

[tip-bot for Lendacky, Thomas]

Commit-ID:  3966c3feca3fd10b2935caa0b4a08c7dd59469e5
Gitweb:     https://git.kernel.org/tip/3966c3feca3fd10b2935caa0b4a08c7dd59469e5
Author:     Lendacky, Thomas <Thomas.Lendacky@amd.com>
AuthorDate: Tue, 2 Apr 2019 15:21:18 +0000
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 10 Apr 2019 13:03:18 +0200

x86/perf/amd: Remove need to check "running" bit in NMI handler

Spurious interrupt support was added to perf in the following commit, almost
a decade ago:

  63e6be6d98e1 ("perf, x86: Catch spurious interrupts after disabling counters")

The two previous patches (resolving the race condition when disabling a
PMC and NMI latency mitigation) allow for the removal of this older
spurious interrupt support.

Currently in x86_pmu_stop(), the bit for the PMC in the active_mask bitmap
is cleared before disabling the PMC, which sets up a race condition. This
race condition was mitigated by introducing the running bitmap. That race
condition can be eliminated by first disabling the PMC, waiting for PMC
reset on overflow and then clearing the bit for the PMC in the active_mask
bitmap. The NMI handler will not re-enable a disabled counter.

If x86_pmu_stop() is called from the perf NMI handler, the NMI latency
mitigation support will guard against any unhandled NMI messages.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org> # 4.14.x-
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: https://lkml.kernel.org/r/Message-ID:
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/events/amd/core.c | 21 +++++++++++++++++++--
 arch/x86/events/core.c     | 13 +++----------
 2 files changed, 22 insertions(+), 12 deletions(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 34c191453ce3..0ecfac84ba91 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -4,8 +4,8 @@
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/delay.h>
-#include <linux/nmi.h>
 #include <asm/apicdef.h>
+#include <asm/nmi.h>
 
 #include "../perf_event.h"
 
@@ -491,6 +491,23 @@ static void amd_pmu_disable_all(void)
 	}
 }
 
+static void amd_pmu_disable_event(struct perf_event *event)
+{
+	x86_pmu_disable_event(event);
+
+	/*
+	 * This can be called from NMI context (via x86_pmu_stop). The counter
+	 * may have overflowed, but either way, we'll never see it get reset
+	 * by the NMI if we're already in the NMI. And the NMI latency support
+	 * below will take care of any pending NMI that might have been
+	 * generated by the overflow.
+	 */
+	if (in_nmi())
+		return;
+
+	amd_pmu_wait_on_overflow(event->hw.idx);
+}
+
 /*
  * Because of NMI latency, if multiple PMC counters are active or other sources
  * of NMIs are received, the perf NMI handler can handle one or more overflowed
@@ -738,7 +755,7 @@ static __initconst const struct x86_pmu amd_pmu = {
 	.disable_all		= amd_pmu_disable_all,
 	.enable_all		= x86_pmu_enable_all,
 	.enable			= x86_pmu_enable_event,
-	.disable		= x86_pmu_disable_event,
+	.disable		= amd_pmu_disable_event,
 	.hw_config		= amd_pmu_hw_config,
 	.schedule_events	= x86_schedule_events,
 	.eventsel		= MSR_K7_EVNTSEL0,
diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index e2b1447192a8..81911e11a15d 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -1349,8 +1349,9 @@ void x86_pmu_stop(struct perf_event *event, int flags)
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	struct hw_perf_event *hwc = &event->hw;
 
-	if (__test_and_clear_bit(hwc->idx, cpuc->active_mask)) {
+	if (test_bit(hwc->idx, cpuc->active_mask)) {
 		x86_pmu.disable(event);
+		__clear_bit(hwc->idx, cpuc->active_mask);
 		cpuc->events[hwc->idx] = NULL;
 		WARN_ON_ONCE(hwc->state & PERF_HES_STOPPED);
 		hwc->state |= PERF_HES_STOPPED;
@@ -1447,16 +1448,8 @@ int x86_pmu_handle_irq(struct pt_regs *regs)
 	apic_write(APIC_LVTPC, APIC_DM_NMI);
 
 	for (idx = 0; idx < x86_pmu.num_counters; idx++) {
-		if (!test_bit(idx, cpuc->active_mask)) {
-			/*
-			 * Though we deactivated the counter some cpus
-			 * might still deliver spurious interrupts still
-			 * in flight. Catch them:
-			 */
-			if (__test_and_clear_bit(idx, cpuc->running))
-				handled++;
+		if (!test_bit(idx, cpuc->active_mask))
 			continue;
-		}
 
 		event = cpuc->events[idx];