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x86/speculation: Merge one test in spectre_v2_user_select_mitigation()

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Merge the test whether the CPU supports STIBP into the test which
determines whether STIBP is required. Thus try to simplify what is
already an insane logic.

Remove a superfluous newline in a comment, while at it.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Anthony Steinhauser <asteinhauser@google.com>
Link: https://lkml.kernel.org/r/20200615065806.GB14668@zn.tnic
This commit is contained in:
Borislav Petkov 2020-06-15 08:51:25 +02:00
parent b3a9e3b962
commit a5ce9f2bb6
1 changed files with 4 additions and 9 deletions
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13
arch/x86/kernel/cpu/bugs.c
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@ -763,10 +763,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
} }
/* /*
* If enhanced IBRS is enabled or SMT impossible, STIBP is not * If no STIBP, enhanced IBRS is enabled or SMT impossible, STIBP is not
* required. * required.
*/ */
if (!smt_possible || spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED) if (!boot_cpu_has(X86_FEATURE_STIBP) ||
!smt_possible ||
spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
return; return;
/* /*
@ -778,12 +780,6 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON))
mode = SPECTRE_V2_USER_STRICT_PREFERRED; mode = SPECTRE_V2_USER_STRICT_PREFERRED;
/*
* If STIBP is not available, clear the STIBP mode.
*/
if (!boot_cpu_has(X86_FEATURE_STIBP))
mode = SPECTRE_V2_USER_NONE;
spectre_v2_user_stibp = mode; spectre_v2_user_stibp = mode;
set_mode: set_mode:
@ -1270,7 +1266,6 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl)
* Indirect branch speculation is always disabled in strict * Indirect branch speculation is always disabled in strict
* mode. It can neither be enabled if it was force-disabled * mode. It can neither be enabled if it was force-disabled
* by a previous prctl call. * by a previous prctl call.
*/ */
if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT || if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT ||
spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT || spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||