[PATCH] x86/cpu/amd: Make erratum #1054 a legacy erratum

From: Kim Phillips
Date: Fri Apr 17 2020 - 10:34:30 EST


Commit

21b5ee59ef18 ("x86/cpu/amd: Enable the fixed Instructions Retired
counter IRPERF")

mistakenly added erratum #1054 as OS Visible Work-around (OSVW)
ID 0. Erratum #1054 is not OSVW ID 0 [1], so make it a legacy
erratum.

There would never have been a false positive on older hardware that
has OSVW bit 0 set, since the IRPERF feature was not available.

We do however save a couple of rdmsrs per thread, on modern system
configurations that correctly set non-zero values in their
OSVW_ID_Length MSRs.

[1] Revision Guide for AMD Family 17h Models 00h-0Fh Processors

The revision guide is available from the bugzilla link below.

Fixes: 21b5ee59ef18 ("x86/cpu/amd: Enable the fixed Instructions Retired counter IRPERF")
Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: Frank van der Linden <fllinden@xxxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
arch/x86/kernel/cpu/amd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 1f875fbe1384..8caf29706eac 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1111,7 +1111,7 @@ static const int amd_erratum_383[] =

/* #1054: Instructions Retired Performance Counter May Be Inaccurate */
static const int amd_erratum_1054[] =
- AMD_OSVW_ERRATUM(0, AMD_MODEL_RANGE(0x17, 0, 0, 0x2f, 0xf));
+ AMD_LEGACY_ERRATUM(AMD_MODEL_RANGE(0x17, 0, 0, 0x2f, 0xf));


static bool cpu_has_amd_erratum(struct cpuinfo_x86 *cpu, const int *erratum)
--
2.20.1