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

Walk the guest page tables via a loop when creating new mappings,
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/20251028225827.2269128-2-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 b418502c5ecc675b8e8afbe0bec9538be0399334..738f2a44083facfe710de7abd36809c013a004cb 100644 (file)
--- a/tools/testing/selftests/kvm/lib/x86/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86/processor.c
@@ -218,8 +218,8 @@ static uint64_t *virt_create_upper_pte(struct kvm_vm *vm,
 void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level)
 {
        const uint64_t pg_size = PG_LEVEL_SIZE(level);
-       uint64_t *pml4e, *pdpe, *pde;
-       uint64_t *pte;
+       uint64_t *pte = &vm->pgd;
+       int current_level;
 
        TEST_ASSERT(vm->mode == VM_MODE_PXXV48_4K,
                    "Unknown or unsupported guest mode, mode: 0x%x", vm->mode);
@@ -243,20 +243,17 @@ void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr, int level)
         * Allocate upper level page tables, if not already present.  Return
         * early if a hugepage was created.
         */
-       pml4e = virt_create_upper_pte(vm, &vm->pgd, vaddr, paddr, PG_LEVEL_512G, level);
-       if (*pml4e & PTE_LARGE_MASK)
-               return;
-
-       pdpe = virt_create_upper_pte(vm, pml4e, vaddr, paddr, PG_LEVEL_1G, level);
-       if (*pdpe & PTE_LARGE_MASK)
-               return;
-
-       pde = virt_create_upper_pte(vm, pdpe, vaddr, paddr, PG_LEVEL_2M, level);
-       if (*pde & PTE_LARGE_MASK)
-               return;
+       for (current_level = vm->pgtable_levels;
+            current_level > PG_LEVEL_4K;
+            current_level--) {
+               pte = virt_create_upper_pte(vm, pte, vaddr, paddr,
+                                           current_level, level);
+               if (*pte & PTE_LARGE_MASK)
+                       return;
+       }
 
        /* Fill in page table entry. */
-       pte = virt_get_pte(vm, pde, vaddr, PG_LEVEL_4K);
+       pte = virt_get_pte(vm, pte, vaddr, PG_LEVEL_4K);
        TEST_ASSERT(!(*pte & PTE_PRESENT_MASK),
                    "PTE already present for 4k page at vaddr: 0x%lx", vaddr);
        *pte = PTE_PRESENT_MASK | PTE_WRITABLE_MASK | (paddr & PHYSICAL_PAGE_MASK);