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x86/bugs: Add SRSO_MITIGATION_NOSMT

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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: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Borislav 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
This commit is contained in:
David Kaplan
2025-06-25 10:58:03 -05:00
committed by Ingo Molnar
parent ab9f2388e0
commit 1fd5eb0286
1 changed files with 4 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
arch/x86/kernel/cpu/bugs.c
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@@ -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]);
}