From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Tue, 7 Mar 2023 17:46:43 +0000
Subject: [PATCH] x86/CPU/AMD: Disable XSAVES on AMD family 0x17
References: bsc#1012628
Patch-mainline: 6.2.7
Git-commit: b0563468eeac88ebc70559d52a0b66efc37e4e9d
commit b0563468eeac88ebc70559d52a0b66efc37e4e9d upstream.
AMD Erratum 1386 is summarised as:
XSAVES Instruction May Fail to Save XMM Registers to the Provided
State Save Area
This piece of accidental chronomancy causes the %xmm registers to
occasionally reset back to an older value.
Ignore the XSAVES feature on all AMD Zen1/2 hardware. The XSAVEC
instruction (which works fine) is equivalent on affected parts.
[ bp: Typos, move it into the F17h-specific function. ]
Reported-by: Tavis Ormandy <taviso@gmail.com>
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20230307174643.1240184-1-andrew.cooper3@citrix.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
arch/x86/kernel/cpu/amd.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index f769d6d0..06f2ede1 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)
--
2.35.3