Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 6fe9e7c2 authored by Jiri Kosina's avatar Jiri Kosina Committed by Borislav Petkov
Browse files

GHES: Make NMI handler have a single reader 



Since GHES sources are global, we theoretically need only a single CPU
reading them per NMI instead of a thundering herd of CPUs waiting on a
spinlock in NMI context for no reason at all.

Do that.

Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
parent 2383844d

drivers/acpi/apei/ghes.c

+7 −5
Original line number Diff line number Diff line
@@ -729,10 +729,10 @@ static struct llist_head ghes_estatus_llist; 
static struct irq_work ghes_proc_irq_work;



/*

 * NMI may be triggered on any CPU, so ghes_nmi_lock is used for

 * mutual exclusion.

 * NMI may be triggered on any CPU, so ghes_in_nmi is used for

 * having only one concurrent reader.

 */

static DEFINE_RAW_SPINLOCK(ghes_nmi_lock);

static atomic_t ghes_in_nmi = ATOMIC_INIT(0);



static LIST_HEAD(ghes_nmi);
@@ -840,7 +840,9 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs) 
	struct ghes *ghes;

	int sev, ret = NMI_DONE;



	raw_spin_lock(&ghes_nmi_lock);

	if (!atomic_add_unless(&ghes_in_nmi, 1, 1))

		return ret;



	list_for_each_entry_rcu(ghes, &ghes_nmi, list) {

		if (ghes_read_estatus(ghes, 1)) {

			ghes_clear_estatus(ghes);
@@ -863,7 +865,7 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs) 
#ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG

	irq_work_queue(&ghes_proc_irq_work);

#endif

	raw_spin_unlock(&ghes_nmi_lock);

	atomic_dec(&ghes_in_nmi);

	return ret;

}