linux-kernel - Re: [PATCH] x86/srso: Correct the mitigation status when SMT is disabled

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Date:   Thu, 17 Aug 2023 11:07:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Nikolay Borisov <nik.borisov@...e.com>, X86 ML <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/srso: Correct the mitigation status when SMT is
 disabled

From: "Borislav Petkov (AMD)" <bp@...en8.de>
Date: Tue, 15 Aug 2023 11:53:13 +0200
Subject: [PATCH] x86/srso: Correct the mitigation status when SMT is disabled

Specify how is SRSO mitigated when SMT is disabled. Also, correct the
SMT check for that.

Fixes: e9fbc47b818b ("x86/srso: Disable the mitigation on unaffected configurations")
Suggested-by: Josh Poimboeuf <jpoimboe@...nel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://lore.kernel.org/r/20230814200813.p5czl47zssuej7nv@treble
---
 arch/x86/kernel/cpu/bugs.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 9026e3fe9f6c..f081d26616ac 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2428,8 +2428,7 @@ static void __init srso_select_mitigation(void)
 		 * Zen1/2 with SMT off aren't vulnerable after the right
 		 * IBPB microcode has been applied.
 		 */
-		if ((boot_cpu_data.x86 < 0x19) &&
-		    (!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED))) {
+		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {
 			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
 			return;
 		}
@@ -2714,7 +2713,7 @@ static ssize_t retbleed_show_state(char *buf)
 static ssize_t srso_show_state(char *buf)
 {
 	if (boot_cpu_has(X86_FEATURE_SRSO_NO))
-		return sysfs_emit(buf, "Not affected\n");
+		return sysfs_emit(buf, "Mitigation: SMT disabled\n");
 
 	return sysfs_emit(buf, "%s%s\n",
 			  srso_strings[srso_mitigation],
-- 
2.42.0.rc0.25.ga82fb66fed25

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette