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Subject[patch 28/30] xen/events: Reduce irq_info::spurious_cnt storage size
To prepare for interrupt spreading reduce the storage size of
irq_info::spurious_cnt to u8 so the required flag for the spreading logic
will not increase the storage size.

Protect the usage site against overruns.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: xen-devel@lists.xenproject.org
---
drivers/xen/events/events_base.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -95,7 +95,7 @@ struct irq_info {
struct list_head list;
struct list_head eoi_list;
short refcnt;
- short spurious_cnt;
+ u8 spurious_cnt;
enum xen_irq_type type; /* type */
unsigned irq;
evtchn_port_t evtchn; /* event channel */
@@ -528,8 +528,10 @@ static void xen_irq_lateeoi_locked(struc
return;

if (spurious) {
- if ((1 << info->spurious_cnt) < (HZ << 2))
- info->spurious_cnt++;
+ if ((1 << info->spurious_cnt) < (HZ << 2)) {
+ if (info->spurious_cnt != 0xFF)
+ info->spurious_cnt++;
+ }
if (info->spurious_cnt > 1) {
delay = 1 << (info->spurious_cnt - 2);
if (delay > HZ)
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