KVM: arm64: Don't retire MMIO instruction w/ pending (emulated) SError

KVM might have an emulated SError queued for the guest if userspace
returned an abort for MMIO. Better yet, it could actually be a
*synchronous* exception in disguise if SCTLR2_ELx.EASE is set.

Don't advance PC if KVM owes an emulated SError, just like the handling
of emulated SEA injection.

Reviewed-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Oliver Upton <[e-mail]>

arch/arm64/kvm/mmio.c

···
 	return data;
 }
 
-static bool kvm_pending_sync_exception(struct kvm_vcpu *vcpu)
+static bool kvm_pending_external_abort(struct kvm_vcpu *vcpu)
 {
 	if (!vcpu_get_flag(vcpu, PENDING_EXCEPTION))
 		return false;
···
 		switch (vcpu_get_flag(vcpu, EXCEPT_MASK)) {
 		case unpack_vcpu_flag(EXCEPT_AA64_EL1_SYNC):
 		case unpack_vcpu_flag(EXCEPT_AA64_EL2_SYNC):
+		case unpack_vcpu_flag(EXCEPT_AA64_EL1_SERR):
+		case unpack_vcpu_flag(EXCEPT_AA64_EL2_SERR):
 			return true;
 		default:
 			return false;
···
 	 * Detect if the MMIO return was already handled or if userspace aborted
 	 * the MMIO access.
 	 */
-	if (unlikely(!vcpu->mmio_needed || kvm_pending_sync_exception(vcpu)))
+	if (unlikely(!vcpu->mmio_needed || kvm_pending_external_abort(vcpu)))
 		return 1;
 
 	vcpu->mmio_needed = 0;