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x86/bugs: Add attack vector controls for L1TF

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Use attack vector controls to determine if L1TF mitigation is required.

Disable SMT if cross-thread protection is desired.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-17-david.kaplan@amd.com
This commit is contained in:
David Kaplan 2025-07-07 13:33:11 -05:00 committed by Borislav Petkov (AMD)
parent fdf99228e2
commit 2f970a5269
1 changed files with 12 additions and 6 deletions
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18
arch/x86/kernel/cpu/bugs.c
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@ -2995,17 +2995,23 @@ static void override_cache_bits(struct cpuinfo_x86 *c)
static void __init l1tf_select_mitigation(void)
{
if (!boot_cpu_has_bug(X86_BUG_L1TF) || cpu_mitigations_off()) {
if (!boot_cpu_has_bug(X86_BUG_L1TF)) {
l1tf_mitigation = L1TF_MITIGATION_OFF;
return;
}
if (l1tf_mitigation == L1TF_MITIGATION_AUTO) {
if (cpu_mitigations_auto_nosmt())
l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
else
l1tf_mitigation = L1TF_MITIGATION_FLUSH;
if (l1tf_mitigation != L1TF_MITIGATION_AUTO)
return;
if (!should_mitigate_vuln(X86_BUG_L1TF)) {
l1tf_mitigation = L1TF_MITIGATION_OFF;
return;
}
if (smt_mitigations == SMT_MITIGATIONS_ON)
l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
else
l1tf_mitigation = L1TF_MITIGATION_FLUSH;
}
static void __init l1tf_apply_mitigation(void)