arm64: KVM: Allow an exit code to be tagged with an SError

Similarily to EL1, an asynchronous abort can be triggered whilst
running at EL2. But instead of making that a new error code,
we need to communicate it to the rest of KVM together with
the exit reason. So let's hijack a single bit that allows the
exception code to be tagged with a "pending SError" information.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

arch/arm64/include/asm/kvm_asm.h

@@ -20,6 +20,10 @@
 
 #include <asm/virt.h>
 
+#define ARM_EXIT_WITH_SERROR_BIT  31
+#define ARM_EXCEPTION_CODE(x)	  ((x) & ~(1U << ARM_EXIT_WITH_SERROR_BIT))
+#define ARM_SERROR_PENDING(x)	  !!((x) & (1U << ARM_EXIT_WITH_SERROR_BIT))
+
 #define ARM_EXCEPTION_IRQ	  0
 #define ARM_EXCEPTION_EL1_SERROR  1
 #define ARM_EXCEPTION_TRAP	  2