3.16.77-rc1 review patch. If anyone has any objections, please let me know.
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From: Josh Poimboeuf jpoimboe@redhat.com
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: Ben Hutchings ben@decadent.org.uk --- arch/x86/kernel/cpu/bugs.c | 4 ---- 1 file changed, 4 deletions(-)
--- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -919,10 +919,6 @@ 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) {