UIE being set can cause maintenance interrupts to occur when Xen writes
to one or more LR registers. The effect is a busy loop around the
interrupt handler in Xen
(http://marc.info/?l=xen-devel&m=141597517132682): everything gets stuck.
Signed-off-by: Stefano Stabellini <stefano.stabell...@eu.citrix.com>
Acked-by: Ian Campbell <ian.campb...@citrix.com>
Reported-and-Tested-by: Andrii Tseglytskyi <andrii.tseglyts...@globallogic.com>
Tested-by: Julien Grall <julien.gr...@linaro.org>
Release-acked-by: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
---
xen/arch/arm/gic.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 70d10d6..e7a1af5 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -403,6 +403,8 @@ void gic_clear_lrs(struct vcpu *v)
if ( is_idle_vcpu(v) )
return;
+ gic_hw_ops->update_hcr_status(GICH_HCR_UIE, 0);
+
spin_lock_irqsave(&v->arch.vgic.lock, flags);
while ((i = find_next_bit((const unsigned long *) &this_cpu(lr_mask),
@@ -527,8 +529,6 @@ void gic_inject(void)
if ( !list_empty(¤t->arch.vgic.lr_pending) && lr_all_full() )
gic_hw_ops->update_hcr_status(GICH_HCR_UIE, 1);
- else
- gic_hw_ops->update_hcr_status(GICH_HCR_UIE, 0);
}
static void do_sgi(struct cpu_user_regs *regs, enum gic_sgi sgi)
@@ -598,6 +598,11 @@ static void maintenance_interrupt(int irq, void *dev_id,
struct cpu_user_regs *r
* Receiving the interrupt is going to cause gic_inject to be called
* on return to guest that is going to clear the old LRs and inject
* new interrupts.
+ *
+ * Do not add code here: maintenance interrupts caused by setting
+ * GICH_HCR_UIE, might read as spurious interrupts (1023) because
+ * GICH_HCR_UIE is cleared before reading GICC_IAR. As a consequence
+ * this handler is not called.
*/
}
--
1.7.10.4
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