KVM: arm64: Re-mask SError after the one instruction window

KVM consumes any SError that were pending during guest exit with a
dsb/isb and unmasking SError. It currently leaves SError unmasked for
the rest of world-switch.

This means any SError that occurs during this part of world-switch
will cause a hyp-panic. We'd much prefer it to remain pending until
we return to the host.
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm64/kvm/hyp/entry.S

@@ -175,6 +175,8 @@ abort_guest_exit_start:
 	.global	abort_guest_exit_end
 abort_guest_exit_end:
 
+	msr	daifset, #4	// Mask aborts
+
 	// If the exception took place, restore the EL1 exception
 	// context so that we can report some information.
 	// Merge the exception code with the SError pending bit.