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x86/speculation/mds: Add SMT warning message

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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>
This commit is contained in:
Josh Poimboeuf 2019-04-02 10:00:51 -05:00 committed by Greg Kroah-Hartman
parent 98c4b3c2ee
commit f8a0bbe4ba
1 changed files with 8 additions and 0 deletions
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8
arch/x86/kernel/cpu/bugs.c
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@ -667,6 +667,9 @@ static void update_indir_branch_cond(void)
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)
{
@ -687,6 +690,8 @@ 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. */
@ -710,6 +715,8 @@ 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:
@ -1139,6 +1146,7 @@ static int __init l1tf_cmdline(char *str)
early_param("l1tf", l1tf_cmdline);
#undef pr_fmt
#define pr_fmt(fmt) fmt
#ifdef CONFIG_SYSFS