PPC KVM fix for 5.7

- Fix a regression introduced in the last merge window, which results
   in guests in HPT mode dying randomly.
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Merge tag 'kvm-ppc-fixes-5.7-1' into topic/ppc-kvm

This brings in a fix from the kvm-ppc tree that was merged to mainline
after rc2, and so isn't in the base of our topic branch. We'd like it
in the topic branch because it interacts with patches we plan to carry
in this branch.

arch/powerpc/kvm/book3s_64_mmu_hv.c

@@ -604,18 +604,19 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	 */
 	local_irq_disable();
 	ptep = __find_linux_pte(vcpu->arch.pgdir, hva, NULL, &shift);
+	pte = __pte(0);
+	if (ptep)
+		pte = *ptep;
+	local_irq_enable();
 	/*
 	 * If the PTE disappeared temporarily due to a THP
 	 * collapse, just return and let the guest try again.
 	 */
-	if (!ptep) {
-		local_irq_enable();
+	if (!pte_present(pte)) {
 		if (page)
 			put_page(page);
 		return RESUME_GUEST;
 	}
-	pte = *ptep;
-	local_irq_enable();
 	hpa = pte_pfn(pte) << PAGE_SHIFT;
 	pte_size = PAGE_SIZE;
 	if (shift)

arch/powerpc/kvm/book3s_64_mmu_radix.c

@@ -815,18 +815,19 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
 	 */
 	local_irq_disable();
 	ptep = __find_linux_pte(vcpu->arch.pgdir, hva, NULL, &shift);
+	pte = __pte(0);
+	if (ptep)
+		pte = *ptep;
+	local_irq_enable();
 	/*
 	 * If the PTE disappeared temporarily due to a THP
 	 * collapse, just return and let the guest try again.
 	 */
-	if (!ptep) {
-		local_irq_enable();
+	if (!pte_present(pte)) {
 		if (page)
 			put_page(page);
 		return RESUME_GUEST;
 	}
-	pte = *ptep;
-	local_irq_enable();
 
 	/* If we're logging dirty pages, always map single pages */
 	large_enable = !(memslot->flags & KVM_MEM_LOG_DIRTY_PAGES);