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x86/srso: Disable the mitigation on unaffected configurations

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commit e9fbc47b818b964ddff5df5b2d5c0f5f32f4a147 upstream.

Skip the srso cmd line parsing which is not needed on Zen1/2 with SMT
disabled and with the proper microcode applied (latter should be the
case anyway) as those are not affected.

Fixes: 5a15d8348881 ("x86/srso: Tie SBPB bit setting to microcode patch detection")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230813104517.3346-1-bp@alien8.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Borislav Petkov (AMD) 2023-08-13 12:39:34 +02:00 committed by Greg Kroah-Hartman
parent e4679a0342
commit dae93ed961
1 changed files with 6 additions and 1 deletions
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7
arch/x86/kernel/cpu/bugs.c
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@ -2399,8 +2399,10 @@ static void __init srso_select_mitigation(void)
* IBPB microcode has been applied.
*/
if ((boot_cpu_data.x86 < 0x19) &&
(!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED)))
(!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED))) {
setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
return;
}
}
if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
@ -2686,6 +2688,9 @@ static ssize_t gds_show_state(char *buf)
static ssize_t srso_show_state(char *buf)
{
if (boot_cpu_has(X86_FEATURE_SRSO_NO))
return sysfs_emit(buf, "Not affected\n");
return sysfs_emit(buf, "%s%s\n",
srso_strings[srso_mitigation],
(cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));