Commit 1fd5eb02 authored by David Kaplan's avatar David Kaplan Committed by Ingo Molnar
Browse files

x86/bugs: Add SRSO_MITIGATION_NOSMT 



AMD Zen1 and Zen2 CPUs with SMT disabled are not vulnerable to SRSO.

Instead of overloading the X86_FEATURE_SRSO_NO bit to indicate this,
define a separate mitigation to make the code cleaner.

Signed-off-by: default avatarDavid Kaplan <david.kaplan@amd.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Cc: H . Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250625155805.600376-2-david.kaplan@amd.com
parent ab9f2388

arch/x86/kernel/cpu/bugs.c

+4 −7
Original line number Diff line number Diff line
@@ -2851,6 +2851,7 @@ enum srso_mitigation { 
	SRSO_MITIGATION_UCODE_NEEDED,

	SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED,

	SRSO_MITIGATION_MICROCODE,

	SRSO_MITIGATION_NOSMT,

	SRSO_MITIGATION_SAFE_RET,

	SRSO_MITIGATION_IBPB,

	SRSO_MITIGATION_IBPB_ON_VMEXIT,
@@ -2862,6 +2863,7 @@ static const char * const srso_strings[] = { 
	[SRSO_MITIGATION_UCODE_NEEDED]		= "Vulnerable: No microcode",

	[SRSO_MITIGATION_SAFE_RET_UCODE_NEEDED]	= "Vulnerable: Safe RET, no microcode",

	[SRSO_MITIGATION_MICROCODE]		= "Vulnerable: Microcode, no safe RET",

	[SRSO_MITIGATION_NOSMT]			= "Mitigation: SMT disabled",

	[SRSO_MITIGATION_SAFE_RET]		= "Mitigation: Safe RET",

	[SRSO_MITIGATION_IBPB]			= "Mitigation: IBPB",

	[SRSO_MITIGATION_IBPB_ON_VMEXIT]	= "Mitigation: IBPB on VMEXIT only",
@@ -2914,8 +2916,7 @@ static void __init srso_select_mitigation(void) 
		 * IBPB microcode has been applied.

		 */

		if (boot_cpu_data.x86 < 0x19 && !cpu_smt_possible()) {

			setup_force_cpu_cap(X86_FEATURE_SRSO_NO);

			srso_mitigation = SRSO_MITIGATION_NONE;

			srso_mitigation = SRSO_MITIGATION_NOSMT;

			return;

		}

	} else {
@@ -2968,8 +2969,7 @@ static void __init srso_update_mitigation(void) 
		srso_mitigation = SRSO_MITIGATION_IBPB;



	if (boot_cpu_has_bug(X86_BUG_SRSO) &&

	    !cpu_mitigations_off() &&

	    !boot_cpu_has(X86_FEATURE_SRSO_NO))

	    !cpu_mitigations_off())

		pr_info("%s\n", srso_strings[srso_mitigation]);

}
@@ -3265,9 +3265,6 @@ 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, "Mitigation: SMT disabled\n");



	return sysfs_emit(buf, "%s\n", srso_strings[srso_mitigation]);

}