x86/speculation/taa: Fix printing of TAA_MSG_SMT on IBRS_ALL CPUs

For new IBRS_ALL CPUs, the Enhanced IBRS check at the beginning of
cpu_bugs_smt_update() causes the function to return early, unintentionally
skipping the MDS and TAA logic.

This is not a problem for MDS, because there appears to be no overlap
between IBRS_ALL and MDS-affected CPUs.  So the MDS mitigation would be
disabled and nothing would need to be done in this function anyway.

But for TAA, the TAA_MSG_SMT string will never get printed on Cascade
Lake and newer.

The check is superfluous anyway: when 'spectre_v2_enabled' is
SPECTRE_V2_IBRS_ENHANCED, 'spectre_v2_user' is always
SPECTRE_V2_USER_NONE, and so the 'spectre_v2_user' switch statement
handles it appropriately by doing nothing.  So just remove the check.

Fixes: 1b42f017415b ("x86/speculation/taa: Add mitigation for TSX Async Abort")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Gbp-Pq: Topic bugfix/x86/taa
Gbp-Pq: Name 0010-x86-speculation-taa-Fix-printing-of-TAA_MSG_SMT-on-I.patch

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 78b0d39d78cd4df8a012395d6a6609cf5b1d059d..bc174dd03fe65001461d04dbf25ebc0a6e7b25be 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -886,10 +886,6 @@ static void update_mds_branch_idle(void)
 
 void arch_smt_update(void)
 {
-       /* Enhanced IBRS implies STIBP. No update required. */
-       if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
-               return;
-
        mutex_lock(&spec_ctrl_mutex);
 
        switch (spectre_v2_user) {