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x86/bugs: Use IBPB for retbleed if used by SRSO

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If spec_rstack_overflow=ibpb then this mitigates retbleed as well.  This
is relevant for AMD Zen1 and Zen2 CPUs which are vulnerable to both bugs.

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/20250625155805.600376-3-david.kaplan@amd.com
This commit is contained in:
David Kaplan 2025-06-25 10:58:04 -05:00 committed by Ingo Molnar
parent 1fd5eb0286
commit ff54ae7314
1 changed files with 19 additions and 15 deletions
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34
arch/x86/kernel/cpu/bugs.c
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@ -1171,6 +1171,21 @@ static enum retbleed_mitigation retbleed_mitigation __ro_after_init =
static int __ro_after_init retbleed_nosmt = false;
enum srso_mitigation {
SRSO_MITIGATION_NONE,
SRSO_MITIGATION_AUTO,
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,
SRSO_MITIGATION_BP_SPEC_REDUCE,
};
static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_AUTO;
static int __init retbleed_parse_cmdline(char *str)
{
if (!str)
@ -1280,6 +1295,10 @@ static void __init retbleed_update_mitigation(void)
if (its_mitigation == ITS_MITIGATION_RETPOLINE_STUFF)
retbleed_mitigation = RETBLEED_MITIGATION_STUFF;
/* If SRSO is using IBPB, that works for retbleed too */
if (srso_mitigation == SRSO_MITIGATION_IBPB)
retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
if (retbleed_mitigation == RETBLEED_MITIGATION_STUFF &&
!cdt_possible(spectre_v2_enabled)) {
pr_err("WARNING: retbleed=stuff depends on retpoline\n");
@ -2845,19 +2864,6 @@ early_param("l1tf", l1tf_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) "Speculative Return Stack Overflow: " fmt
enum srso_mitigation {
SRSO_MITIGATION_NONE,
SRSO_MITIGATION_AUTO,
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,
SRSO_MITIGATION_BP_SPEC_REDUCE,
};
static const char * const srso_strings[] = {
[SRSO_MITIGATION_NONE] = "Vulnerable",
[SRSO_MITIGATION_UCODE_NEEDED] = "Vulnerable: No microcode",
@ -2870,8 +2876,6 @@ static const char * const srso_strings[] = {
[SRSO_MITIGATION_BP_SPEC_REDUCE] = "Mitigation: Reduced Speculation"
};
static enum srso_mitigation srso_mitigation __ro_after_init = SRSO_MITIGATION_AUTO;
static int __init srso_parse_cmdline(char *str)
{
if (!str)