[SRU][J][PATCH v2 04/20] x86/CPU/AMD: Carve out the erratum 1386 fix

[Juerg Haefliger]

From: "Borislav Petkov (AMD)" <bp at alien8.de>

Call it on the affected CPU generations.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp at alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov at suse.com>
Link: http://lore.kernel.org/r/20231120104152.13740-3-bp@alien8.de
(backported from commit a7c32a1ae9ee43abfe884f5af376877c4301d166)
[juergh: Adjusted context due to commit:
 4a3beb84ba8e ("x86/CPU/AMD: Improve the erratum 1386 workaround")]
CVE-2024-53114
Signed-off-by: Juerg Haefliger <juerg.haefliger at canonical.com>
---
 arch/x86/kernel/cpu/amd.c | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 9399defbf173..000f7643a2b6 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1042,6 +1042,25 @@ static const struct x86_cpu_desc erratum_1386_microcode[] = {
 	{},
 };
 
+static void fix_erratum_1386(struct cpuinfo_x86 *c)
+{
+	/*
+	 * 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 the feature flag only on microcode revisions which
+	 * don't have the fix.
+	 */
+	if (x86_cpu_has_min_microcode_rev(erratum_1386_microcode))
+		return;
+
+	clear_cpu_cap(c, X86_FEATURE_XSAVES);
+}
+
 void init_spectral_chicken(struct cpuinfo_x86 *c)
 {
 #ifdef CONFIG_CPU_UNRET_ENTRY
@@ -1062,21 +1081,6 @@ 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 the feature flag only on microcode revisions which
-	 * don't have the fix.
-	 */
-	if (x86_cpu_has_min_microcode_rev(erratum_1386_microcode))
-		return;
-
-	clear_cpu_cap(c, X86_FEATURE_XSAVES);
 }
 
 static void init_amd_zn(struct cpuinfo_x86 *c)
@@ -1145,10 +1149,12 @@ static void zenbleed_check(struct cpuinfo_x86 *c)
 
 static void init_amd_zen(struct cpuinfo_x86 *c)
 {
+	fix_erratum_1386(c);
 }
 
 static void init_amd_zen2(struct cpuinfo_x86 *c)
 {
+	fix_erratum_1386(c);
 }
 
 static void init_amd_zen3(struct cpuinfo_x86 *c)
-- 
2.48.1