KVM: selftests: Use a loop to walk guest page tables

Walk the guest page tables via a loop when searching for a PTE,
instead of using unique variables for each level of the page tables.

This simplifies the code and makes it easier to support 5-level paging
in the future.

Signed-off-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Link: https://patch.msgid.link/20251028225827.2269128-3-jmattson@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c
index 738f2a44083facfe710de7abd36809c013a004cb..720c678187b500f706b2c0b822090e7d3dc84225 100644 (file)
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -307,7 +307,8 @@ static bool vm_is_target_pte(uint64_t *pte, int *level, int current_level)
 uint64_t *__vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr,
                                    int *level)
 {
-       uint64_t *pml4e, *pdpe, *pde;
+       uint64_t *pte = &vm->pgd;
+       int current_level;
 
        TEST_ASSERT(!vm->arch.is_pt_protected,
                    "Walking page tables of protected guests is impossible");
@@ -328,19 +329,15 @@ uint64_t *__vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr,
        TEST_ASSERT(vaddr == (((int64_t)vaddr << 16) >> 16),
                "Canonical check failed.  The virtual address is invalid.");
 
-       pml4e = virt_get_pte(vm, &vm->pgd, vaddr, PG_LEVEL_512G);
-       if (vm_is_target_pte(pml4e, level, PG_LEVEL_512G))
-               return pml4e;
-
-       pdpe = virt_get_pte(vm, pml4e, vaddr, PG_LEVEL_1G);
-       if (vm_is_target_pte(pdpe, level, PG_LEVEL_1G))
-               return pdpe;
-
-       pde = virt_get_pte(vm, pdpe, vaddr, PG_LEVEL_2M);
-       if (vm_is_target_pte(pde, level, PG_LEVEL_2M))
-               return pde;
+       for (current_level = vm->pgtable_levels;
+            current_level > PG_LEVEL_4K;
+            current_level--) {
+               pte = virt_get_pte(vm, pte, vaddr, current_level);
+               if (vm_is_target_pte(pte, level, current_level))
+                       return pte;
+       }
 
-       return virt_get_pte(vm, pde, vaddr, PG_LEVEL_4K);
+       return virt_get_pte(vm, pte, vaddr, PG_LEVEL_4K);
 }
 
 uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr)