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Commit b9faa465 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Greg Kroah-Hartman
Browse files

x86/speculation/mds: Add SMT warning message 



commit 39226ef02bfb43248b7db12a4fdccb39d95318e3 upstream

MDS is vulnerable with SMT.  Make that clear with a one-time printk
whenever SMT first gets enabled.

Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarTyler Hicks <tyhicks@canonical.com>
Acked-by: default avatarJiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b3a63d9c

arch/x86/kernel/cpu/bugs.c

+8 −0
Original line number Diff line number Diff line
@@ -659,6 +659,9 @@ 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)

{
@@ -679,6 +682,8 @@ 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. */
@@ -702,6 +707,8 @@ 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:
@@ -1131,6 +1138,7 @@ static int __init l1tf_cmdline(char *str) 
early_param("l1tf", l1tf_cmdline);



#undef pr_fmt

#define pr_fmt(fmt) fmt



#ifdef CONFIG_SYSFS