Commit a6673429 authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar

perf/x86: Add /sys/devices/cpu/rdpmc=2 to allow rdpmc for all tasks

While perfmon2 is a sufficiently evil library (it pokes MSRs
directly) that breaking it is fair game, it's still useful, so we
might as well try to support it.  This allows users to write 2 to
/sys/devices/cpu/rdpmc to disable all rdpmc protection so that hack
like perfmon2 can continue to work.

At some point, if perf_event becomes fast enough to replace
perfmon2, then this can go.
Signed-off-by: default avatarAndy Lutomirski <>
Signed-off-by: default avatarPeter Zijlstra (Intel) <>
Cc: Paul Mackerras <>
Cc: Arnaldo Carvalho de Melo <>
Cc: Kees Cook <>
Cc: Andrea Arcangeli <>
Cc: Vince Weaver <>
Cc: "hillf.zj" <>
Cc: Valdis Kletnieks <>
Cc: Linus Torvalds <>
Link: Ingo Molnar's avatarIngo Molnar <>
parent 7911d3f7
......@@ -19,9 +19,12 @@ static inline void paravirt_activate_mm(struct mm_struct *prev,
#endif /* !CONFIG_PARAVIRT */
extern struct static_key rdpmc_always_available;
static inline void load_mm_cr4(struct mm_struct *mm)
if (atomic_read(&mm->context.perf_rdpmc_allowed))
if (static_key_true(&rdpmc_always_available) ||
......@@ -45,6 +45,8 @@ DEFINE_PER_CPU(struct cpu_hw_events, cpu_hw_events) = {
.enabled = 1,
struct static_key rdpmc_always_available = STATIC_KEY_INIT_FALSE;
u64 __read_mostly hw_cache_event_ids
......@@ -1870,10 +1872,27 @@ static ssize_t set_attr_rdpmc(struct device *cdev,
if (ret)
return ret;
if (val > 2)
return -EINVAL;
if (x86_pmu.attr_rdpmc_broken)
return -ENOTSUPP;
x86_pmu.attr_rdpmc = !!val;
if ((val == 2) != (x86_pmu.attr_rdpmc == 2)) {
* Changing into or out of always available, aka
* perf-event-bypassing mode. This path is extremely slow,
* but only root can trigger it, so it's okay.
if (val == 2)
on_each_cpu(refresh_pce, NULL, 1);
x86_pmu.attr_rdpmc = val;
return count;
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