[tip: irq/core] irqchip/gic-v4.1: Skip absent CPUs while iterating over redistributors

[tip-bot2 for Marc Zyngier]

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     28d160de5194c68ff534443d2a8b6f1d10d57c58
Gitweb:        https://git.kernel.org/tip/28d160de5194c68ff534443d2a8b6f1d10d57c58
Author:        Marc Zyngier <maz@xxxxxxxxxx>
AuthorDate:    Wed, 04 Mar 2020 20:33:09 
Committer:     Marc Zyngier <maz@xxxxxxxxxx>
CommitterDate: Thu, 19 Mar 2020 11:21:58 

irqchip/gic-v4.1: Skip absent CPUs while iterating over redistributors

In a system that is only sparsly populated with CPUs, we can end-up with
redistributors structures that are not initialized. Let's make sure we
don't try and access those when iterating over them (in this case when
checking we have a L2 VPE table).

Fixes: 4e6437f12d6e ("irqchip/gic-v4.1: Ensure L2 vPE table is allocated at RD level")
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Reviewed-by: Zenghui Yu <yuzenghui@xxxxxxxxxx>
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20200304203330.4967-3-maz@xxxxxxxxxx
---
 drivers/irqchip/irq-gic-v3-its.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 83b1186..da883a6 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -2452,6 +2452,10 @@ static bool allocate_vpe_l2_table(int cpu, u32 id)
 	if (!gic_rdists->has_rvpeid)
 		return true;
 
+	/* Skip non-present CPUs */
+	if (!base)
+		return true;
+
 	val  = gicr_read_vpropbaser(base + SZ_128K + GICR_VPROPBASER);
 
 	esz  = FIELD_GET(GICR_VPROPBASER_4_1_ENTRY_SIZE, val) + 1;