diff mbox series

[4.19,07/33] x86/speculation: Use generic retpoline by default on AMD

Message ID 20220310140807.965113257@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

gregkh@linuxfoundation.org March 10, 2022, 2:18 p.m. UTC 
From: Kim Phillips <kim.phillips@amd.com>

commit 244d00b5dd4755f8df892c86cab35fb2cfd4f14b upstream.

AMD retpoline may be susceptible to speculation. The speculation
execution window for an incorrect indirect branch prediction using
LFENCE/JMP sequence may potentially be large enough to allow
exploitation using Spectre V2.

By default, don't use retpoline,lfence on AMD.  Instead, use the
generic retpoline.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/kernel/cpu/bugs.c |    8 --------
 1 file changed, 8 deletions(-)
diff mbox series

Patch

--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -898,14 +898,6 @@  static enum spectre_v2_mitigation __init
 		return SPECTRE_V2_NONE;
 	}
 
-	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD) {
-		if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
-			pr_err("LFENCE not serializing, switching to generic retpoline\n");
-			return SPECTRE_V2_RETPOLINE;
-		}
-		return SPECTRE_V2_LFENCE;
-	}
-
 	return SPECTRE_V2_RETPOLINE;
 }