Commit 69129794 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Ingo Molnar
Browse files

x86/bugs: Fix BHI retpoline check 



Confusingly, X86_FEATURE_RETPOLINE doesn't mean retpolines are enabled,
as it also includes the original "AMD retpoline" which isn't a retpoline
at all.

Also replace cpu_feature_enabled() with boot_cpu_has() because this is
before alternatives are patched and cpu_feature_enabled()'s fallback
path is slower than plain old boot_cpu_has().

Fixes: ec9404e4 ("x86/bhi: Add BHI mitigation knob")
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Reviewed-by: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/ad3807424a3953f0323c011a643405619f2a4927.1712944776.git.jpoimboe@kernel.org
parent 7211274f

arch/x86/kernel/cpu/bugs.c

+7 −4
Original line number Diff line number Diff line
@@ -1652,7 +1652,8 @@ static void __init bhi_select_mitigation(void) 
		return;



	/* Retpoline mitigates against BHI unless the CPU has RRSBA behavior */

	if (cpu_feature_enabled(X86_FEATURE_RETPOLINE)) {

	if (boot_cpu_has(X86_FEATURE_RETPOLINE) &&

	    !boot_cpu_has(X86_FEATURE_RETPOLINE_LFENCE)) {

		spec_ctrl_disable_kernel_rrsba();

		if (rrsba_disabled)

			return;
@@ -2808,7 +2809,9 @@ static const char *spectre_bhi_state(void) 
		return "; BHI: BHI_DIS_S";

	else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP))

		return "; BHI: SW loop, KVM: SW loop";

	else if (boot_cpu_has(X86_FEATURE_RETPOLINE) && rrsba_disabled)

	else if (boot_cpu_has(X86_FEATURE_RETPOLINE) &&

		 !boot_cpu_has(X86_FEATURE_RETPOLINE_LFENCE) &&

		 rrsba_disabled)

		return "; BHI: Retpoline";

	else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP_ON_VMEXIT))

		return "; BHI: Vulnerable, KVM: SW loop";