On Wed, Sep 17, 2025 at 02:48:38PM -0700, Jim Mattson wrote:
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
.../testing/selftests/kvm/lib/x86/processor.c | 21 +++++++------------ 1 file changed, 8 insertions(+), 13 deletions(-)
diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c b/tools/testing/selftests/kvm/lib/x86/processor.c index 0238e674709d..433365c8196d 100644 --- a/tools/testing/selftests/kvm/lib/x86/processor.c +++ b/tools/testing/selftests/kvm/lib/x86/processor.c @@ -270,7 +270,8 @@ 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"); @@ -291,19 +292,13 @@ 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 > 0; current_level--) {
This should be current_level >= PG_LEVEL_4K. It's the same, but easier to read.
pte = virt_get_pte(vm, pte, vaddr, current_level);if (vm_is_target_pte(pte, level, current_level))
Seems like vm_is_target_pte() is written with the assumption that it operates on an upper-level PTE, but I think it works on 4K PTEs as well.
return pte;- }
- return virt_get_pte(vm, pde, vaddr, PG_LEVEL_4K);
- return pte;
} uint64_t *vm_get_page_table_entry(struct kvm_vm *vm, uint64_t vaddr) -- 2.51.0.470.ga7dc726c21-goog