irqchip/gic-v3-its: Gracefully fail on LPI exhaustion

mainline inclusion
from mainline-5.0
commit 45725e0fc3e7
category: bugfix
bugzilla: 9453
CVE: NA

-------------------------------------------------

In the unlikely event that we cannot find any available LPI in the
system, we should gracefully return an error instead of carrying
on with no LPI allocated at all.

Fixes: 38dd7c49 ("irqchip/gic-v3-its: Drop chunk allocation compatibility")
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NBixuan Cui <cuibixuan@huawei.com>
Reviewed-by: NHanjun Guo <guohanjun@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/irqchip/irq-gic-v3-its.c

@@ -1586,6 +1586,9 @@ static unsigned long *its_lpi_alloc(int nr_irqs, u32 *base, int *nr_ids)
 		nr_irqs /= 2;
 	} while (nr_irqs > 0);
 
+	if (!nr_irqs)
+		err = -ENOSPC;
+
 	if (err)
 		goto out;