diff options
authorPeter Zijlstra <peterz@infradead.org>2018-01-14 11:27:13 +0100
committerThomas Gleixner <tglx@linutronix.de>2018-01-14 11:42:10 +0100
commit99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8 (patch)
parenta237f762681e2a394ca67f21df2feb2b76a3609b (diff)
x86,perf: Disable intel_bts when PTI
The intel_bts driver does not use the 'normal' BTS buffer which is exposed through the cpu_entry_area but instead uses the memory allocated for the perf AUX buffer. This obviously comes apart when using PTI because then the kernel mapping; which includes that AUX buffer memory; disappears. Fixing this requires to expose a mapping which is visible in all context and that's not trivial. As a quick fix disable this driver when PTI is enabled to prevent malfunction. Fixes: 385ce0ea4c07 ("x86/mm/pti: Add Kconfig") Reported-by: Vince Weaver <vincent.weaver@maine.edu> Reported-by: Robert Święcki <robert@swiecki.net> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: greg@kroah.com Cc: hughd@google.com Cc: luto@amacapital.net Cc: Vince Weaver <vince@deater.net> Cc: torvalds@linux-foundation.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20180114102713.GB6166@worktop.programming.kicks-ass.net
1 files changed, 18 insertions, 0 deletions
diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 141e07b06216..24ffa1e88cf9 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -582,6 +582,24 @@ static __init int bts_init(void)
if (!boot_cpu_has(X86_FEATURE_DTES64) || !x86_pmu.bts)
return -ENODEV;
+ if (boot_cpu_has(X86_FEATURE_PTI)) {
+ /*
+ * BTS hardware writes through a virtual memory map we must
+ * either use the kernel physical map, or the user mapping of
+ * the AUX buffer.
+ *
+ * However, since this driver supports per-CPU and per-task inherit
+ * we cannot use the user mapping since it will not be availble
+ * if we're not running the owning process.
+ *
+ * With PTI we can't use the kernal map either, because its not
+ * there when we run userspace.
+ *
+ * For now, disable this driver when using PTI.
+ */
+ return -ENODEV;
+ }
bts_pmu.capabilities = PERF_PMU_CAP_AUX_NO_SG | PERF_PMU_CAP_ITRACE |
bts_pmu.task_ctx_nr = perf_sw_context;