[PATCH AUTOSEL 6.14 23/34] x86/bugs: Use SBPB in write_ibpb() if applicable

Sasha Levin
2025-04-14T13:27:05Z

From: Josh Poimboeuf <jpoimboe@kernel.org>

[ Upstream commit fc9fd3f98423367c79e0bd85a9515df26dc1b3cc ]

write_ibpb() does IBPB, which (among other things) flushes branch type
predictions on AMD. If the CPU has SRSO_NO, or if the SRSO mitigation
has been disabled, branch type flushing isn't needed, in which case the
lighter-weight SBPB can be used.

The 'x86_pred_cmd' variable already keeps track of whether IBPB or SBPB
should be used. Use that instead of hardcoding IBPB.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/17c5dcd14b29199b75199d67ff7758de9d9a4928.1744148254.git.jpoimboe@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/entry/entry.S | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/entry/entry.S b/arch/x86/entry/entry.S
index b7ea3e8e9eccd..58e3124ee2b42 100644
--- a/arch/x86/entry/entry.S
+++ b/arch/x86/entry/entry.S
@@ -18,7 +18,7 @@

SYM_FUNC_START(entry_ibpb)
movl $MSR_IA32_PRED_CMD, %ecx
- movl $PRED_CMD_IBPB, %eax
+ movl _ASM_RIP(x86_pred_cmd), %eax
xorl %edx, %edx
wrmsr

--
2.39.5