linux-kernel - [PATCH] irqchip/gic-v3-its: Clear Valid before writing any bits else in VPENDBASER

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Date:   Mon, 24 Feb 2020 10:50:29 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     <kvmarm@...ts.cs.columbia.edu>, <maz@...nel.org>
CC:     <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <wanghaibin.wang@...wei.com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Yanlei Jia <jiayanlei@...wei.com>
Subject: [PATCH] irqchip/gic-v3-its: Clear Valid before writing any bits else in VPENDBASER

The Valid bit must be cleared before changing anything else when writing
GICR_VPENDBASER to avoid the UNPREDICTABLE behavior. This is exactly what
we've done on 32bit arm, but not on arm64.

This works fine on GICv4 where we only clear Valid for a vPE deschedule.
With the introduction of GICv4.1, we might also need to talk something else
(e.g., PendingLast, Doorbell) to the redistributor when clearing the Valid.
Let's port the 32bit gicr_write_vpendbaser() to arm64 so that hardware can
do the right thing after descheduling the vPE.

Cc: Yanlei Jia <jiayanlei@...wei.com>
Signed-off-by: Zenghui Yu <yuzenghui@...wei.com>
---
 arch/arm64/include/asm/arch_gicv3.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/arch_gicv3.h b/arch/arm64/include/asm/arch_gicv3.h
index 25fec4bde43a..effe66e1ca58 100644
--- a/arch/arm64/include/asm/arch_gicv3.h
+++ b/arch/arm64/include/asm/arch_gicv3.h
@@ -143,7 +143,18 @@ static inline u32 gic_read_rpr(void)
 #define gicr_write_vpropbaser(v, c)	writeq_relaxed(v, c)
 #define gicr_read_vpropbaser(c)		readq_relaxed(c)
 
-#define gicr_write_vpendbaser(v, c)	writeq_relaxed(v, c)
+#define gicr_write_vpendbaser(v, c) do {		\
+	u64 tmp = readq_relaxed(c);			\
+							\
+	/* Clear Valid before writing any bits else. */	\
+	if (tmp & GICR_VPENDBASER_Valid) {		\
+		tmp &= ~GICR_VPENDBASER_Valid;		\
+		writeq_relaxed(tmp, c);			\
+	}						\
+							\
+	writeq_relaxed(v, c);				\
+} while (0)
+
 #define gicr_read_vpendbaser(c)		readq_relaxed(c)
 
 static inline bool gic_prio_masking_enabled(void)
-- 
2.19.1