commit d7caac991feeef1b871ee6988fd2c9725df09039
author Peter Zijlstra <peterz@infradead.org> Tue Jun 14 23:16:04 2022 +0200
committer Borislav Petkov <bp@suse.de> Mon Jun 27 10:34:00 2022 +0200
tree 3898bfd6d98b4721394662c2af34ab2c69fbc558
parent a09a6e2399ba0595c3042b3164f3ca68a3cff33e

x86/cpu/amd: Add Spectral Chicken

Zen2 uarchs have an undocumented, unnamed, MSR that contains a chicken
bit for some speculation behaviour. It needs setting.

Note: very belatedly AMD released naming; it's now officially called
      MSR_AMD64_DE_CFG2 and MSR_AMD64_DE_CFG2_SUPPRESS_NOBR_PRED_BIT
      but shall remain the SPECTRAL CHICKEN.

Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>

arch/x86/include/asm/msr-index.h

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 059c7e5..7b411d9 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -568,6 +568,9 @@
 /* Fam 17h MSRs */
 #define MSR_F17H_IRPERF			0xc00000e9
 
+#define MSR_ZEN2_SPECTRAL_CHICKEN	0xc00110e3
+#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT	BIT_ULL(1)
+
 /* Fam 16h MSRs */
 #define MSR_F16H_L2I_PERF_CTL		0xc0010230
 #define MSR_F16H_L2I_PERF_CTR		0xc0010231