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x86/bugs: Add attack vector controls for retbleed

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Use attack vector controls to determine if retbleed mitigation is
required.

Disable SMT if cross-thread protection is desired and STIBP is not
available.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-13-david.kaplan@amd.com
This commit is contained in:
David Kaplan
2025-07-07 13:33:07 -05:00
committed by Borislav Petkov (AMD)
parent 19a5f3ea43
commit 9687eb2399
1 changed files with 8 additions and 3 deletions
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11
arch/x86/kernel/cpu/bugs.c
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@@ -1313,7 +1313,7 @@ early_param("retbleed", retbleed_parse_cmdline);
static void __init retbleed_select_mitigation(void)
{
if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off()) {
if (!boot_cpu_has_bug(X86_BUG_RETBLEED)) {
retbleed_mitigation = RETBLEED_MITIGATION_NONE;
return;
}
@@ -1350,6 +1350,11 @@ static void __init retbleed_select_mitigation(void)
if (retbleed_mitigation != RETBLEED_MITIGATION_AUTO)
return;
if (!should_mitigate_vuln(X86_BUG_RETBLEED)) {
retbleed_mitigation = RETBLEED_MITIGATION_NONE;
return;
}
/* Intel mitigation selected in retbleed_update_mitigation() */
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
@@ -1373,7 +1378,7 @@ static void __init retbleed_select_mitigation(void)
static void __init retbleed_update_mitigation(void)
{
if (!boot_cpu_has_bug(X86_BUG_RETBLEED) || cpu_mitigations_off())
if (!boot_cpu_has_bug(X86_BUG_RETBLEED))
return;
/* ITS can also enable stuffing */
@@ -1468,7 +1473,7 @@ static void __init retbleed_apply_mitigation(void)
}
if (mitigate_smt && !boot_cpu_has(X86_FEATURE_STIBP) &&
(retbleed_nosmt || cpu_mitigations_auto_nosmt()))
(retbleed_nosmt || smt_mitigations == SMT_MITIGATIONS_ON))
cpu_smt_disable(false);
}