linux-kernel - [PATCH] irqchip/gic-v3: Fix priority comparison when non-secure priorities are used

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Message-Id: <20210811171505.1502090-1-wenst@chromium.org>
Date:   Thu, 12 Aug 2021 01:15:05 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Thomas Gleixner <tglx@...utronix.de>, Marc Zyngier <maz@...nel.org>
Cc:     Chen-Yu Tsai <wenst@...omium.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] irqchip/gic-v3: Fix priority comparison when non-secure priorities are used

When non-secure priorities are used, compared to the raw priority set,
the value read back from RPR is also right-shifted by one and the
highest bit set.

Add a macro to do the modifications to the raw priority when doing the
comparison against the RPR value. This corrects the pseudo-NMI behavior
when non-secure priorities in the GIC are used. Tested on 5.10 with
the "IPI as pseudo-NMI" series [1] applied on MT8195.

[1] https://lore.kernel.org/linux-arm-kernel/1604317487-14543-1-git-send-email-sumit.garg@linaro.org/

Fixes: 336780590990 ("irqchip/gic-v3: Support pseudo-NMIs when SCR_EL3.FIQ == 0")
Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
---
 drivers/irqchip/irq-gic-v3.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
index e0f4debe64e1..e7a0b55413db 100644
--- a/drivers/irqchip/irq-gic-v3.c
+++ b/drivers/irqchip/irq-gic-v3.c
@@ -100,6 +100,15 @@ EXPORT_SYMBOL(gic_pmr_sync);
 DEFINE_STATIC_KEY_FALSE(gic_nonsecure_priorities);
 EXPORT_SYMBOL(gic_nonsecure_priorities);
 
+#define GICD_INT_RPR_PRI(priority)					\
+	({								\
+		u32 __priority = (priority);				\
+		if (static_branch_unlikely(&gic_nonsecure_priorities))	\
+			__priority = 0x80 | (__priority >> 1);		\
+									\
+		__priority;						\
+	})
+
 /* ppi_nmi_refs[n] == number of cpus having ppi[n + 16] set as NMI */
 static refcount_t *ppi_nmi_refs;
 
@@ -687,7 +696,7 @@ static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs
 		return;
 
 	if (gic_supports_nmi() &&
-	    unlikely(gic_read_rpr() == GICD_INT_NMI_PRI)) {
+	    unlikely(gic_read_rpr() == GICD_INT_RPR_PRI(GICD_INT_NMI_PRI))) {
 		gic_handle_nmi(irqnr, regs);
 		return;
 	}
-- 
2.32.0.605.g8dce9f2422-goog