| Message ID | 20230113171026.582290-2-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures with swap PTEs | expand |
On 13.01.23 18:10, David Hildenbrand wrote: > We want to implement __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures. > Let's extend our sanity checks, especially testing that our PTE bit > does not affect: > * is_swap_pte() -> pte_present() and pte_none() > * the swap entry + type > * pte_swp_soft_dirty() > > Especially, the pfn_pte() is dodgy when the swap PTE layout differs > heavily from ordinary PTEs. Let's properly construct a swap PTE from > swap type+offset. > > Signed-off-by: David Hildenbrand <david@redhat.com> > --- The following fixup for !CONFIG_SWAP on top, which makes it compile for me and passes when booting on x86_64 with CONFIG_DEBUG_VM_PGTABLE: ... [ 0.347112] Loaded X.509 cert 'Build time autogenerated kernel key: ee6afc0578f6475656fec8a4f9d02832' [ 0.350112] debug_vm_pgtable: [debug_vm_pgtable ]: Validating architecture page table helpers [ 0.351217] page_owner is disabled ... From 6a6162e8af62a4b3f7b9d823fdfae86de3f34a9d Mon Sep 17 00:00:00 2001 From: David Hildenbrand <david@redhat.com> Date: Sat, 14 Jan 2023 16:47:12 +0100 Subject: [PATCH] fixup: mm/debug_vm_pgtable: more pte_swp_exclusive() sanity checks generic_max_swapfile_size() is only available with CONFIG_SWAP -- which makes sense, because without SWAP there are no swap files. Let's simply probe manually which bits we can obtain after storing them in a PTE, and properly call it "max swap offset", which is more generic for a swap entry. Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/debug_vm_pgtable.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index 3da0cc380c35..af59cc7bd307 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -810,15 +810,17 @@ static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) { static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args) { - unsigned long max_swapfile_size = generic_max_swapfile_size(); + unsigned long max_swap_offset; swp_entry_t entry, entry2; pte_t pte; pr_debug("Validating PTE swap exclusive\n"); + /* See generic_max_swapfile_size(): probe the maximum offset */ + max_swap_offset = swp_offset(pte_to_swp_entry(swp_entry_to_pte(swp_entry(0, ~0UL)))); + /* Create a swp entry with all possible bits set */ - entry = swp_entry((1 << MAX_SWAPFILES_SHIFT) - 1, - max_swapfile_size - 1); + entry = swp_entry((1 << MAX_SWAPFILES_SHIFT) - 1, max_swap_offset); pte = swp_entry_to_pte(entry); WARN_ON(pte_swp_exclusive(pte));
diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c index bb3328f46126..a0730beffd78 100644 --- a/mm/debug_vm_pgtable.c +++ b/mm/debug_vm_pgtable.c @@ -811,13 +811,34 @@ static void __init pmd_swap_soft_dirty_tests(struct pgtable_debug_args *args) { static void __init pte_swap_exclusive_tests(struct pgtable_debug_args *args) { #ifdef __HAVE_ARCH_PTE_SWP_EXCLUSIVE - pte_t pte = pfn_pte(args->fixed_pte_pfn, args->page_prot); + unsigned long max_swapfile_size = generic_max_swapfile_size(); + swp_entry_t entry, entry2; + pte_t pte; pr_debug("Validating PTE swap exclusive\n"); + + /* Create a swp entry with all possible bits set */ + entry = swp_entry((1 << MAX_SWAPFILES_SHIFT) - 1, + max_swapfile_size - 1); + + pte = swp_entry_to_pte(entry); + WARN_ON(pte_swp_exclusive(pte)); + WARN_ON(!is_swap_pte(pte)); + entry2 = pte_to_swp_entry(pte); + WARN_ON(memcmp(&entry, &entry2, sizeof(entry))); + pte = pte_swp_mkexclusive(pte); WARN_ON(!pte_swp_exclusive(pte)); + WARN_ON(!is_swap_pte(pte)); + WARN_ON(pte_swp_soft_dirty(pte)); + entry2 = pte_to_swp_entry(pte); + WARN_ON(memcmp(&entry, &entry2, sizeof(entry))); + pte = pte_swp_clear_exclusive(pte); WARN_ON(pte_swp_exclusive(pte)); + WARN_ON(!is_swap_pte(pte)); + entry2 = pte_to_swp_entry(pte); + WARN_ON(memcmp(&entry, &entry2, sizeof(entry))); #endif /* __HAVE_ARCH_PTE_SWP_EXCLUSIVE */ }
We want to implement __HAVE_ARCH_PTE_SWP_EXCLUSIVE on all architectures. Let's extend our sanity checks, especially testing that our PTE bit does not affect: * is_swap_pte() -> pte_present() and pte_none() * the swap entry + type * pte_swp_soft_dirty() Especially, the pfn_pte() is dodgy when the swap PTE layout differs heavily from ordinary PTEs. Let's properly construct a swap PTE from swap type+offset. Signed-off-by: David Hildenbrand <david@redhat.com> --- mm/debug_vm_pgtable.c | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-)