diff mbox series

[5.4,21/37] x86/speculation: Fix SPEC_CTRL write on SMT state change

Message ID 20221003131038.12645-22-cascardo@canonical.com (mailing list archive)
State New, archived
Headers show
Series IBRS support // Retbleed mitigations | expand

Commit Message

Thadeu Lima de Souza Cascardo Oct. 3, 2022, 1:10 p.m. UTC 
From: Josh Poimboeuf <jpoimboe@kernel.org>

commit 56aa4d221f1ee2c3a49b45b800778ec6e0ab73c5 upstream.

If the SMT state changes, SSBD might get accidentally disabled.  Fix
that.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
---
 arch/x86/kernel/cpu/bugs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 5f8ea848d30b..6c6fe963fd0e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1335,7 +1335,8 @@  static void __init spectre_v2_select_mitigation(void)
 
 static void update_stibp_msr(void * __unused)
 {
-	write_spec_ctrl_current(x86_spec_ctrl_base, true);
+	u64 val = spec_ctrl_current() | (x86_spec_ctrl_base & SPEC_CTRL_STIBP);
+	write_spec_ctrl_current(val, true);
 }
 
 /* Update x86_spec_ctrl_base in case SMT state changed. */