Re: [PATCH -v2 1/2] x86, microcode: Sanitize per-cpu microcodereloading interface

From: Peter Zijlstra
Date: Fri Jun 22 2012 - 11:47:10 EST

What about something like so on top of those two microcode_core patches?

Since we don't have to worry about per-cpu loads, we can do a single
callback after the entire machine is updated.

---
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 | 49 ++++++++++++++++++++++++++++++---
arch/x86/kernel/microcode_core.c | 10 ++++--
5 files changed, 72 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
@@ -378,7 +378,7 @@ 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 */
@@ -1649,13 +1649,20 @@ 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,
@@ -1663,11 +1670,11 @@ 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 +1714,54 @@ 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) {
+ 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)
+ pebs_broken |= intel_snb_pebs_broken(cpu);
+ 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 micro-code update\n");
+ x86_pmu.pebs_broken = 0;
+ } else {
+ pr_info("PEBS disabled due to CPU errata, please upgrade micro-code\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@xxxxxxxxxxxxxxxxxxxx>");
@@ -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(&microcode_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(&microcode_mutex);

return err;
}
@@ -309,6 +308,7 @@ static ssize_t reload_store(struct devic
return size;

get_online_cpus();
+ mutex_lock(&microcode_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(&microcode_mutex);
put_online_cpus();

if (!ret)
@@ -557,7 +560,8 @@ static int __init microcode_init(void)
mutex_lock(&microcode_mutex);

error = subsys_interface_register(&mc_cpu_interface);
-
+ if (!error)
+ perf_check_microcode();
mutex_unlock(&microcode_mutex);
put_online_cpus();


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