arm64: KVM: Add synchronization on translation regime change for erratum 1165522

In order to ensure that slipping HCR_EL2.TGE is done at the right
time when switching translation regime, let insert the required ISBs
that will be patched in when erratum 1165522 is detected.

Take this opportunity to add the missing include of asm/alternative.h
which was getting there by pure luck.

Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/include/asm/kvm_hyp.h

@@ -20,6 +20,7 @@
 
 #include <linux/compiler.h>
 #include <linux/kvm_host.h>
+#include <asm/alternative.h>
 #include <asm/sysreg.h>
 
 #define __hyp_text __section(.hyp.text) notrace
@@ -163,6 +164,13 @@ static __always_inline void __hyp_text __load_guest_stage2(struct kvm *kvm)
 {
 	write_sysreg(kvm->arch.vtcr, vtcr_el2);
 	write_sysreg(kvm->arch.vttbr, vttbr_el2);
+
+	/*
+	 * ARM erratum 1165522 requires the actual execution of the above
+	 * before we can switch to the EL1/EL0 translation regime used by
+	 * the guest.
+	 */
+	asm(ALTERNATIVE("nop", "isb", ARM64_WORKAROUND_1165522));
 }
 
 #endif /* __ARM64_KVM_HYP_H__ */