linux-kernel - [PATCH v5 02/23] irqchip/gic-v4.1: Skip absent CPUs while iterating over redistributors

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Date:   Wed,  4 Mar 2020 20:33:09 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jason Cooper <jason@...edaemon.net>,
        Robert Richter <rrichter@...vell.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Eric Auger <eric.auger@...hat.com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Subject: [PATCH v5 02/23] 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@...nel.org>
Reviewed-by: Zenghui Yu <yuzenghui@...wei.com>
---
 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 83b1186ffcad..da883a691028 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;
-- 
2.20.1