Merge tag 'x86_urgent_for_v6.3_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fix from Borislav Petkov:
 "A single erratum fix for AMD machines:

   - Disable XSAVES on AMD Zen1 and Zen2 machines due to an erratum. No
     impact to anything as those machines will fallback to XSAVEC which
     is equivalent there"

* tag 'x86_urgent_for_v6.3_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/CPU/AMD: Disable XSAVES on AMD family 0x17

1 files changed, 9 insertions, 0 deletions

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 380753b14cab..95cdd08c4cbb 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -880,6 +880,15 @@ void init_spectral_chicken(struct cpuinfo_x86 *c)
 		}
 	}
 #endif
+	/*
+	 * Work around Erratum 1386.  The XSAVES instruction malfunctions in
+	 * certain circumstances on Zen1/2 uarch, and not all parts have had
+	 * updated microcode at the time of writing (March 2023).
+	 *
+	 * Affected parts all have no supervisor XSAVE states, meaning that
+	 * the XSAVEC instruction (which works fine) is equivalent.
+	 */
+	clear_cpu_cap(c, X86_FEATURE_XSAVES);
 }
 
 static void init_amd_zn(struct cpuinfo_x86 *c)