[linux-yocto] [yocto-4.12][PATCH 3/3] x86/intel_rdt: Turn off most RDT features on Skylake

[quanyang.wang at windriver.com]

From: Tony Luck <tony.luck at intel.com>

commit d56593eb5eda8f593db92927059697bbf89bc4b3 upstream

Errata list is included in this document:
https://www.intel.com/content/dam/www/public/us/en/documents/specification-updates/6th-gen-x-series-spec-update.pdf
with more details in:
https://www.intel.com/content/www/us/en/processors/xeon/scalable/xeon-scalable-spec-update.html

But the tl;dr summary (using tags from first of the documents) is:
SKZ4  MBM does not accurately track write bandwidth
SKZ17 CMT counters may not count accurately
SKZ18 CAT may not restrict cacheline allocation under certain conditions
SKZ19 MBM counters may undercount

Disable all these features on Skylake models. Users who understand the
errata may re-enable using boot command line options.

Signed-off-by: Tony Luck <tony.luck at intel.com>
Cc: Fenghua" <fenghua.yu at intel.com>
Cc: Ravi V" <ravi.v.shankar at intel.com>
Cc: "Peter Zijlstra" <peterz at infradead.org>
Cc: "Stephane Eranian" <eranian at google.com>
Cc: "Andi Kleen" <ak at linux.intel.com>
Cc: "David Carrillo-Cisneros" <davidcc at google.com>
Cc: Vikas Shivappa <vikas.shivappa at linux.intel.com>
Link: http://lkml.kernel.org/r/3aea0a3bae219062c812668bd9b7b8f1a25003ba.1503512900.git.tony.luck@intel.com
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
---
 arch/x86/kernel/cpu/intel_rdt.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/cpu/intel_rdt.c b/arch/x86/kernel/cpu/intel_rdt.c
index f15c61d..88dcf84 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -770,6 +770,9 @@ static __init void rdt_quirks(void)
 		if (!rdt_options[RDT_FLAG_L3_CAT].force_off)
 			cache_alloc_hsw_probe();
 		break;
+	case INTEL_FAM6_SKYLAKE_X:
+		if (boot_cpu_data.x86_mask <= 4)
+			set_rdt_options("!cmt,!mbmtotal,!mbmlocal,!l3cat");
 	}
 }
 
-- 
1.9.1