[PATCH v3 18/19] xen/arm: Prevent slipping hypervisor SError to guest

[Wei Chen <Wei.Chen@arm.com>]

If there is a pending SError while we're returning from trap. If the
SError handle option is "DIVERSE", we have to prevent slipping this
hypervisor SError to guest. So we have to use the dsb/isb to guarantee
that the pending hypervisor SError would be caught in hypervisor before
return to guest.

In previous patch, we will set SKIP_CHECK_PENDING_VSERROR to cpu_hwcaps
when option is NOT "DIVERSE". This means we can use the alternative to
skip synchronizing SErrors for other SErrors handle options.

Because we have umasked the Abort/SError bit in previous patch. We have
to disable the Abort/SError before returning to guest as we have done
for IRQ.

Signed-off-by: Wei Chen <Wei.Chen@arm.com>

---
v2->v3:
1. Use alternative instead of check serror_op to skip sychronizing SErrors
   while option is NOT "DIVERSE".
2. Disable Abort/SError before returning to guest.
---
 xen/arch/arm/traps.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 2c610c4..8f1a0cd 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2936,6 +2936,19 @@ asmlinkage void leave_hypervisor_tail(void)
         local_irq_disable();
         if (!softirq_pending(smp_processor_id())) {
             gic_inject();
+
+            /*
+             * If the SErrors handle option is "DIVERSE", we have to prevent
+             * slipping the hypervisor SError to guest. In this option, before
+             * returning from trap, we have to synchronize SErrors to guarantee
+             * that the pending SError would be caught in hypervisor.
+             *
+             * If option is NOT "DIVERSE", SKIP_CHECK_PENDING_VSERROR will be
+             * set to cpu_hwcaps. This means we can use the alternative to skip
+             * synchronizing SErrors for other SErrors handle options.
+             */
+            SYNCHRONIZE_SERROR(SKIP_CHECK_PENDING_VSERROR);
+
             return;
         }
         local_irq_enable();
-- 
2.7.4


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