[RFC 5/8] xen/arm: gic: Document how gic_set_irq_type should be called

From: Julien Grall <julien.grall@arm.com>
To: xen-devel@lists.xen.org
Cc: sstabellini@kernel.org, wei.chen@arm.com, steve.capper@arm.com,
	Julien Grall <julien.grall@arm.com>,
	shannon.zhao@linaro.org, shankerd@codeaurora.org
Subject: [RFC 5/8] xen/arm: gic: Document how gic_set_irq_type should be called
Date: Tue,  7 Jun 2016 17:48:40 +0100	[thread overview]
Message-ID: <1465318123-3090-6-git-send-email-julien.grall@arm.com> (raw)
In-Reply-To: <1465318123-3090-1-git-send-email-julien.grall@arm.com>

Changing the value of Int_config is UNPREDICTABLE when the corresponding
interrupt is not disabled.

The driver is assuming the interrupt will be disabled by the caller of
gic_set_irq_type. Add an ASSERT to ensure it.

Signed-off-by: Julien Grall <julien.grall@arm.com>
---
 xen/arch/arm/gic.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 8b992d8..27cd177 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -96,8 +96,14 @@ void gic_restore_state(struct vcpu *v)
     gic_restore_pending_irqs(v);
 }
 
+/* desc->irq needs to be disabled before calling this function */
 static void gic_set_irq_type(struct irq_desc *desc, unsigned int type)
 {
+    /*
+     * IRQ must be disabled before configuring it (see 4.3.13 in ARM IHI
+     * 0048B.b). We rely on the caller to do it.
+     */
+    ASSERT(test_bit(_IRQ_DISABLED, &desc->status));
     ASSERT(spin_is_locked(&desc->lock));
     ASSERT(type != IRQ_TYPE_INVALID);
 
-- 
1.9.1


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