KVM: arm/arm64: Only clean the dcache on translation fault

The only case where we actually need to perform a dcache maintenance
is when we map the page for the first time, and subsequent permission
faults do not require cache maintenance. Let's make it conditional
on not being a permission fault (and thus a translation fault).
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

virt/kvm/arm/mmu.c

@@ -1400,7 +1400,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			new_pmd = kvm_s2pmd_mkwrite(new_pmd);
 			kvm_set_pfn_dirty(pfn);
 		}
-		clean_dcache_guest_page(vcpu, pfn, PMD_SIZE);
+
+		if (fault_status != FSC_PERM)
+			clean_dcache_guest_page(vcpu, pfn, PMD_SIZE);
 
 		if (exec_fault) {
 			new_pmd = kvm_s2pmd_mkexec(new_pmd);
@@ -1416,7 +1418,9 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
 			kvm_set_pfn_dirty(pfn);
 			mark_page_dirty(kvm, gfn);
 		}
-		clean_dcache_guest_page(vcpu, pfn, PAGE_SIZE);
+
+		if (fault_status != FSC_PERM)
+			clean_dcache_guest_page(vcpu, pfn, PAGE_SIZE);
 
 		if (exec_fault) {
 			new_pte = kvm_s2pte_mkexec(new_pte);