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Date: Tue, 26 Jun 2012 23:46:18 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Borislav Petkov <bp@...64.org>
Cc: X86-ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
LKML <linux-kernel@...r.kernel.org>,
Andreas Herrmann <andreas.herrmann3@....com>,
Henrique de Moraes Holschuh <hmh@....eng.br>,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH -v2 1/2] x86, microcode: Sanitize per-cpu microcode
reloading interface
On Tue, 2012-06-26 at 21:40 +0200, Borislav Petkov wrote:
>
> > +void perf_check_microcode(void)
> > +{
> > + if (x86_pmu.check_microcode)
> > + x86_pmu.check_microcode();
> > +}
> > +EXPORT_SYMBOL_GPL(perf_check_microcode);
>
> Maybe we should call the after-ucode-has-been-updated callback something
> like arch_verify_microcode_revision or something similar and move it to
> generic x86 code so that other stuff can use it too, in the future...
>
> Although I'm not aware of any other users right about now.
Like that notifier list I had earlier? Yeah we can do that if more users
show up.
> > @@ -373,7 +375,7 @@ struct x86_pmu {
> > * Intel DebugStore bits
> > */
> > int bts, pebs;
> > - int bts_active, pebs_active;
> > + int bts_active, pebs_active, pebs_broken;
>
> I know you don't like bool's here but maybe make it a bitfield like the
> one in perf_event_attr?
I added another patch doing just that:
---
Subject: perf, x86: Save a few bytes in struct x86_pmu
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Tue Jun 26 23:38:39 CEST 2012
All these are basically boolean flags, use a bitfield to save a few
bytes.
Suggested-by: Borislav Petkov <bp@...64.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
arch/x86/kernel/cpu/perf_event.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -374,8 +374,11 @@ struct x86_pmu {
/*
* Intel DebugStore bits
*/
- int bts, pebs;
- int bts_active, pebs_active, pebs_broken;
+ int bts :1,
+ bts_active :1,
+ pebs :1,
+ pebs_active :1,
+ pebs_broken :1;
int pebs_record_size;
void (*drain_pebs)(struct pt_regs *regs);
struct event_constraint *pebs_constraints;
---
> > int pebs_record_size;
> > void (*drain_pebs)(struct pt_regs *regs);
> > struct event_constraint *pebs_constraints;
> > --- a/arch/x86/kernel/cpu/perf_event_intel.c
> > +++ b/arch/x86/kernel/cpu/perf_event_intel.c
> > @@ -1714,11 +1714,54 @@ static __init void intel_clovertown_quir
> > x86_pmu.pebs_constraints = NULL;
> > }
> >
> > +static int intel_snb_pebs_broken(int cpu)
> > +{
> > + u32 rev = UINT_MAX; /* default to broken for unknown models */
> > +
> > + switch (cpu_data(cpu).x86_model) {
>
> cpu_data(cpu) does a per_cpu access three times in this function, maybe
> declare a local ptr which saves us the next two derefs... (if the
> compiler is not optimizing those, anyway, that is).
I was hoping for CSE optimization to do that for me.. its not really a
performance critical path anyway. I could change it if people think it
reads better with regular: struct cpuinfo_x86 *c = &cpu_data(cpu);
> > + get_online_cpus();
> > + for_each_online_cpu(cpu)
> > + pebs_broken |= intel_snb_pebs_broken(cpu);
>
> if pebs_broken gets set here not on the last cpu, you could break out of
> the loop early instead of iterating to the last cpu.
Right you are..
---
Subject: perf, x86: Add a microcode revision check for SNB-PEBS
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Date: Fri Jun 08 14:50:50 CEST 2012
Recent Intel microcode resolved the SNB-PEBS issues, so conditionally
enable PEBS on SNB hardware depending on the microcode revision.
Thanks to Stephane for figuring out the various microcode revisions.
Cc: Stephane Eranian <eranian@...gle.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
arch/x86/include/asm/perf_event.h | 2 +
arch/x86/kernel/cpu/perf_event.c | 21 +++++++++----
arch/x86/kernel/cpu/perf_event.h | 4 +-
arch/x86/kernel/cpu/perf_event_intel.c | 51 +++++++++++++++++++++++++++++++--
arch/x86/kernel/microcode_core.c | 10 ++++--
5 files changed, 74 insertions(+), 14 deletions(-)
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -232,6 +232,7 @@ struct perf_guest_switch_msr {
extern struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr);
extern void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap);
+extern void perf_check_microcode(void);
#else
static inline perf_guest_switch_msr *perf_guest_get_msrs(int *nr)
{
@@ -245,6 +246,7 @@ static inline void perf_get_x86_pmu_capa
}
static inline void perf_events_lapic_init(void) { }
+static inline void perf_check_microcode(void) { }
#endif
#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_AMD)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -379,7 +379,7 @@ int x86_pmu_hw_config(struct perf_event
int precise = 0;
/* Support for constant skid */
- if (x86_pmu.pebs_active) {
+ if (x86_pmu.pebs_active && !x86_pmu.pebs_broken) {
precise++;
/* Support for IP fixup */
@@ -1650,13 +1650,20 @@ static void x86_pmu_flush_branch_stack(v
x86_pmu.flush_branch_stack();
}
+void perf_check_microcode(void)
+{
+ if (x86_pmu.check_microcode)
+ x86_pmu.check_microcode();
+}
+EXPORT_SYMBOL_GPL(perf_check_microcode);
+
static struct pmu pmu = {
.pmu_enable = x86_pmu_enable,
.pmu_disable = x86_pmu_disable,
- .attr_groups = x86_pmu_attr_groups,
+ .attr_groups = x86_pmu_attr_groups,
- .event_init = x86_pmu_event_init,
+ .event_init = x86_pmu_event_init,
.add = x86_pmu_add,
.del = x86_pmu_del,
@@ -1664,11 +1671,11 @@ static struct pmu pmu = {
.stop = x86_pmu_stop,
.read = x86_pmu_read,
- .start_txn = x86_pmu_start_txn,
- .cancel_txn = x86_pmu_cancel_txn,
- .commit_txn = x86_pmu_commit_txn,
+ .start_txn = x86_pmu_start_txn,
+ .cancel_txn = x86_pmu_cancel_txn,
+ .commit_txn = x86_pmu_commit_txn,
- .event_idx = x86_pmu_event_idx,
+ .event_idx = x86_pmu_event_idx,
.flush_branch_stack = x86_pmu_flush_branch_stack,
};
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -361,6 +361,8 @@ struct x86_pmu {
void (*cpu_starting)(int cpu);
void (*cpu_dying)(int cpu);
void (*cpu_dead)(int cpu);
+
+ void (*check_microcode)(void);
void (*flush_branch_stack)(void);
/*
@@ -373,7 +375,7 @@ struct x86_pmu {
* Intel DebugStore bits
*/
int bts, pebs;
- int bts_active, pebs_active;
+ int bts_active, pebs_active, pebs_broken;
int pebs_record_size;
void (*drain_pebs)(struct pt_regs *regs);
struct event_constraint *pebs_constraints;
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1714,11 +1714,56 @@ static __init void intel_clovertown_quir
x86_pmu.pebs_constraints = NULL;
}
+static int intel_snb_pebs_broken(int cpu)
+{
+ u32 rev = UINT_MAX; /* default to broken for unknown models */
+
+ switch (cpu_data(cpu).x86_model) {
+ case 42: /* SNB */
+ rev = 0x28;
+ break;
+
+ case 45: /* SNB-EP */
+ switch (cpu_data(cpu).x86_mask) {
+ case 6: rev = 0x618; break;
+ case 7: rev = 0x70c; break;
+ }
+ }
+
+ return (cpu_data(cpu).microcode < rev);
+}
+
+static void intel_snb_check_microcode(void)
+{
+ int pebs_broken = 0;
+ int cpu;
+
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ if ((pebs_broken = intel_snb_pebs_broken(cpu)))
+ break;
+ }
+ put_online_cpus();
+
+ if (pebs_broken == x86_pmu.pebs_broken)
+ return;
+
+ /*
+ * Serialized by the microcode lock..
+ */
+ if (x86_pmu.pebs_broken) {
+ pr_info("PEBS enabled due to microcode update\n");
+ x86_pmu.pebs_broken = 0;
+ } else {
+ pr_info("PEBS disabled due to CPU errata, please upgrade microcode\n");
+ x86_pmu.pebs_broken = 1;
+ }
+}
+
static __init void intel_sandybridge_quirk(void)
{
- pr_warn("PEBS disabled due to CPU errata\n");
- x86_pmu.pebs = 0;
- x86_pmu.pebs_constraints = NULL;
+ x86_pmu.check_microcode = intel_snb_check_microcode;
+ intel_snb_check_microcode();
}
static const struct { int id; char *name; } intel_arch_events_map[] __initconst = {
--- a/arch/x86/kernel/microcode_core.c
+++ b/arch/x86/kernel/microcode_core.c
@@ -87,6 +87,7 @@
#include <asm/microcode.h>
#include <asm/processor.h>
#include <asm/cpu_device_id.h>
+#include <asm/perf_event.h>
MODULE_DESCRIPTION("Microcode Update Driver");
MODULE_AUTHOR("Tigran Aivazian <tigran@...azian.fsnet.co.uk>");
@@ -277,7 +278,6 @@ static int reload_for_cpu(int cpu)
struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
int err = 0;
- mutex_lock(µcode_mutex);
if (uci->valid) {
enum ucode_state ustate;
@@ -288,7 +288,6 @@ static int reload_for_cpu(int cpu)
if (ustate == UCODE_ERROR)
err = -EINVAL;
}
- mutex_unlock(µcode_mutex);
return err;
}
@@ -309,6 +308,7 @@ static ssize_t reload_store(struct devic
return size;
get_online_cpus();
+ mutex_lock(µcode_mutex);
for_each_online_cpu(cpu) {
tmp_ret = reload_for_cpu(cpu);
if (tmp_ret != 0)
@@ -318,6 +318,9 @@ static ssize_t reload_store(struct devic
if (!ret)
ret = tmp_ret;
}
+ if (!ret)
+ perf_check_microcode();
+ mutex_unlock(µcode_mutex);
put_online_cpus();
if (!ret)
@@ -557,7 +560,8 @@ static int __init microcode_init(void)
mutex_lock(µcode_mutex);
error = subsys_interface_register(&mc_cpu_interface);
-
+ if (!error)
+ perf_check_microcode();
mutex_unlock(µcode_mutex);
put_online_cpus();
--
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