KVM/arm64 fixes for 5.9, take #3

- Fix synchronization of VTTBR update on TLB invalidation for nVHE systems
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Merge tag 'kvmarm-fixes-5.9-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm into kvm-master

KVM/arm64 fixes for 5.9, take #3

- Fix synchronization of VTTBR update on TLB invalidation for nVHE systems

arch/arm64/kvm/hyp/nvhe/tlb.c

@@ -31,7 +31,14 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu *mmu,
 		isb();
 	}
 
+	/*
+	 * __load_guest_stage2() includes an ISB only when the AT
+	 * workaround is applied. Take care of the opposite condition,
+	 * ensuring that we always have an ISB, but not two ISBs back
+	 * to back.
+	 */
 	__load_guest_stage2(mmu);
+	asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
 }
 
 static void __tlb_switch_to_host(struct tlb_inv_context *cxt)