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: ec9404e40e8f ("x86/bhi: Add BHI mitigation knob")
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Pawan 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

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ca295b0c1eeee05b812c27bb88bd814dba3c1f00..ab18185894dfd5e9c3f09f5fa39ac4c8ef72e7f4 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -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;
@@ -2804,11 +2805,13 @@ static const char *spectre_bhi_state(void)
 {
        if (!boot_cpu_has_bug(X86_BUG_BHI))
                return "; BHI: Not affected";
-       else if  (boot_cpu_has(X86_FEATURE_CLEAR_BHB_HW))
+       else if (boot_cpu_has(X86_FEATURE_CLEAR_BHB_HW))
                return "; BHI: BHI_DIS_S";
-       else if  (boot_cpu_has(X86_FEATURE_CLEAR_BHB_LOOP))
+       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";