On Tue, Oct 21, 2025 at 03:11:56PM -0700, Jim Mattson wrote: > On Mon, Oct 20, 2025 at 10:21 AM Yosry Ahmed <[email protected]> wrote: > > > > 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 <[email protected]> > > > --- > > > .../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. > > I believe it does. Would you prefer that I exit the loop before > PG_LEVEL_4K and restore the virt_get_pte() below?
Slightly. Only because virt_get_pte() checks the large bit and uses terminology like "hugepage", so I think using it for 4K PTEs is a bit confusing. Not a big deal either way tho. > > > > + 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 > > >
