Commit a5ce9f2b authored by Borislav Petkov's avatar Borislav Petkov
Browse files

x86/speculation: Merge one test in spectre_v2_user_select_mitigation() 



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: default avatarBorislav Petkov <bp@suse.de>
Cc: Anthony Steinhauser <asteinhauser@google.com>
Link: https://lkml.kernel.org/r/20200615065806.GB14668@zn.tnic
parent b3a9e3b9

arch/x86/kernel/cpu/bugs.c

+4 −9
Original line number Diff line number Diff line
@@ -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.

	 */

	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;



	/*
@@ -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))

		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;



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

		 * mode. It can neither be enabled if it was force-disabled

		 * by a  previous prctl call.



		 */

		if (spectre_v2_user_ibpb == SPECTRE_V2_USER_STRICT ||

		    spectre_v2_user_stibp == SPECTRE_V2_USER_STRICT ||

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