perf/x86/amd/ibs: Handle erratum torvalds#420 only on the affected CPU family (10h)

commit e431e79 upstream.

This saves us writing the IBS control MSR twice when disabling the
event.

I searched revision guides for all families since 10h, and did not
find occurrence of erratum torvalds#420, nor anything remotely similar:
so we isolate the secondary MSR write to family 10h only.

Also unconditionally update the count mask for IBS Op implementations
that have read & writeable current count (CurCnt) fields in addition
to the MaxCnt field.  These bits were reserved on prior
implementations, and therefore shouldn't have negative impact.

Signed-off-by: Kim Phillips <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Fixes: c9574fe ("perf/x86-ibs: Implement workaround for IBS erratum torvalds#420")
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
[bwh: Backported to 3.16:
 - Don't update the count mask; we don't use or define the CurCnt fields here
 - Adjust filename]
Signed-off-by: Ben Hutchings <[email protected]>

Author: kimphillamd

arch/x86/kernel/cpu/perf_event_amd_ibs.c

@@ -351,7 +351,8 @@ static inline void perf_ibs_disable_event(struct perf_ibs *perf_ibs,
 					  struct hw_perf_event *hwc, u64 config)
 {
 	config &= ~perf_ibs->cnt_mask;
-	wrmsrl(hwc->config_base, config);
+	if (boot_cpu_data.x86 == 0x10)
+		wrmsrl(hwc->config_base, config);
 	config &= ~perf_ibs->enable_mask;
 	wrmsrl(hwc->config_base, config);
 }