From 56aa4d221f1ee2c3a49b45b800778ec6e0ab73c5 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Tue, 14 Jun 2022 23:16:07 +0200 Subject: [PATCH] x86/speculation: Fix SPEC_CTRL write on SMT state change If the SMT state changes, SSBD might get accidentally disabled. Fix that. Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov --- arch/x86/kernel/cpu/bugs.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 108bd74289c50..9b80059c4e02d 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1458,7 +1458,8 @@ 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. */ -- 2.30.2