KVM: selftests: aarch64: Add virt_get_pte_hva() library function

Add a library function to get the PTE (a host virtual address) of a
given GVA.  This will be used in a future commit by a test to clear and
check the access flag of a particular page.
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Andrew Jones <andrew.jones@linux.dev>
Signed-off-by: Ricardo Koller <ricarkol@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221017195834.2295901-3-ricarkol@google.com

tools/testing/selftests/kvm/include/aarch64/processor.h

@@ -109,6 +109,8 @@ void vm_install_exception_handler(struct kvm_vm *vm,
 void vm_install_sync_handler(struct kvm_vm *vm,
 		int vector, int ec, handler_fn handler);
 
+uint64_t *virt_get_pte_hva(struct kvm_vm *vm, vm_vaddr_t gva);
+
 static inline void cpu_relax(void)
 {
 	asm volatile("yield" ::: "memory");

tools/testing/selftests/kvm/lib/aarch64/processor.c

@@ -138,7 +138,7 @@ void virt_arch_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr)
 	_virt_pg_map(vm, vaddr, paddr, attr_idx);
 }
 
-vm_paddr_t addr_arch_gva2gpa(struct kvm_vm *vm, vm_vaddr_t gva)
+uint64_t *virt_get_pte_hva(struct kvm_vm *vm, vm_vaddr_t gva)
 {
 	uint64_t *ptep;
 
@@ -169,11 +169,18 @@ vm_paddr_t addr_arch_gva2gpa(struct kvm_vm *vm, vm_vaddr_t gva)
 		TEST_FAIL("Page table levels must be 2, 3, or 4");
 	}
 
-	return pte_addr(vm, *ptep) + (gva & (vm->page_size - 1));
+	return ptep;
 
 unmapped_gva:
 	TEST_FAIL("No mapping for vm virtual address, gva: 0x%lx", gva);
-	exit(1);
+	exit(EXIT_FAILURE);
+}
+
+vm_paddr_t addr_arch_gva2gpa(struct kvm_vm *vm, vm_vaddr_t gva)
+{
+	uint64_t *ptep = virt_get_pte_hva(vm, gva);
+
+	return pte_addr(vm, *ptep) + (gva & (vm->page_size - 1));
 }
 
 static void pte_dump(FILE *stream, struct kvm_vm *vm, uint8_t indent, uint64_t page, int level)