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

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commit 012206a822a8b6ac09125bfaa210a95b9eb8f1c1 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf 2019-11-06 20:26:46 -06:00 committed by Greg Kroah-Hartman
parent aa6ca7b9a9
commit 9b81a067dc
1 changed files with 0 additions and 4 deletions
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4
arch/x86/kernel/cpu/bugs.c
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@ -874,10 +874,6 @@ 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) {