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Subject[PATCH 3/3] x86/intel_rdt: Turn off most RDT features on Skylake
From: Tony Luck <>

Errata list is included in this document:
with more details in:

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 <>
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 65222d8fd5ec..a55b74ca0973 100644
--- a/arch/x86/kernel/cpu/intel_rdt.c
+++ b/arch/x86/kernel/cpu/intel_rdt.c
@@ -767,6 +767,9 @@ static __init void rdt_quirks(void)
if (!rdt_options[RDT_FLAG_L3_CAT].force_off)
+ if (boot_cpu_data.x86_mask <= 4)
+ set_rdt_options("!cmt,!mbmtotal,!mbmlocal,!l3cat");

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