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Commit 71d79539 authored by Borislav Petkov's avatar Borislav Petkov Committed by Greg Kroah-Hartman
Browse files

x86/speculation: Merge one test in spectre_v2_user_select_mitigation() 



commit a5ce9f2bb665d1d2b31f139a02dbaa2dfbb62fa6 upstream.

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


[fllinden@amazon.com: fixed contextual conflict (comment) for 4.19]
Signed-off-by: default avatarFrank van der Linden <fllinden@amazon.com>
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cdba3260

arch/x86/kernel/cpu/bugs.c

+4 −9
Original line number Diff line number Diff line
@@ -755,10 +755,12 @@ 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;



	/*
@@ -770,12 +772,6 @@ 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:
@@ -1254,7 +1250,6 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) 
		if (spectre_v2_user_ibpb == SPECTRE_V2_USER_NONE &&

		    spectre_v2_user_stibp == SPECTRE_V2_USER_NONE)

			return 0;



		/*

		 * With strict mode for both IBPB and STIBP, the instruction

		 * code paths avoid checking this task flag and instead,