From: Josh Poimboeuf jpoimboe@redhat.com
commit 39226ef02bfb43248b7db12a4fdccb39d95318e3 upstream.
MDS is vulnerable with SMT. Make that clear with a one-time printk whenever SMT first gets enabled.
Signed-off-by: Josh Poimboeuf jpoimboe@redhat.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Reviewed-by: Tyler Hicks tyhicks@canonical.com Acked-by: Jiri Kosina jkosina@suse.cz Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/bugs.c | 8 ++++++++ 1 file changed, 8 insertions(+)
--- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -646,6 +646,9 @@ static void update_indir_branch_cond(voi static_branch_disable(&switch_to_cond_stibp); }
+#undef pr_fmt +#define pr_fmt(fmt) fmt + /* Update the static key controlling the MDS CPU buffer clear in idle */ static void update_mds_branch_idle(void) { @@ -666,6 +669,8 @@ static void update_mds_branch_idle(void) static_branch_disable(&mds_idle_clear); }
+#define MDS_MSG_SMT "MDS CPU bug present and SMT on, data leak possible. See https://www.kernel.org/doc/html/latest/admin-guide/hw-vuln/mds.html for more details.\n" + void arch_smt_update(void) { /* Enhanced IBRS implies STIBP. No update required. */ @@ -689,6 +694,8 @@ void arch_smt_update(void) switch (mds_mitigation) { case MDS_MITIGATION_FULL: case MDS_MITIGATION_VMWERV: + if (sched_smt_active() && !boot_cpu_has(X86_BUG_MSBDS_ONLY)) + pr_warn_once(MDS_MSG_SMT); update_mds_branch_idle(); break; case MDS_MITIGATION_OFF: @@ -1069,6 +1076,7 @@ static void __init l1tf_select_mitigatio setup_force_cpu_cap(X86_FEATURE_L1TF_PTEINV); } #undef pr_fmt +#define pr_fmt(fmt) fmt
#ifdef CONFIG_SYSFS