x86,perf: Disable intel_bts when PTI
authorPeter Zijlstra <peterz@infradead.org>
Sun, 14 Jan 2018 10:27:13 +0000 (11:27 +0100)
committerThomas Gleixner <tglx@linutronix.de>
Sun, 14 Jan 2018 10:42:10 +0000 (11:42 +0100)
commit99a9dc98ba52267ce5e062b52de88ea1f1b2a7d8
tree6bd2808c08f2182cf046bf68e1a9db84e2d40e64
parenta237f762681e2a394ca67f21df2feb2b76a3609b
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
arch/x86/events/intel/bts.c