From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Date: Sat, 14 Jan 2023 16:09:35 +0000 Subject: Re: [PATCH mm-unstable v1 01/26] mm/debug_vm_pgtable: more pte_swp_exclusive() sanity checks Message-Id: <6aaad548-cf48-77fa-9d6c-db83d724b2eb@redhat.com> List-Id: References: <20230113171026.582290-1-david@redhat.com> <20230113171026.582290-2-david@redhat.com> In-Reply-To: <20230113171026.582290-2-david@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-kernel@vger.kernel.org Cc: Andrew Morton , Hugh Dickins , John Hubbard , Jason Gunthorpe , Mike Rapoport , Yang Shi , Vlastimil Babka , Nadav Amit , Andrea Arcangeli , Peter Xu , linux-mm@kvack.org, x86@kernel.org, linux-alpha@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-hexagon@vger.kernel.org, linux-ia64@vger.kernel.org, loongarch@lists.linux.dev, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, openrisc@lists.librecores.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, linux-xtensa@linux-xtensa.org 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 > --- 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 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 Signed-off-by: David Hildenbrand --- 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)); -- 2.39.0 -- Thanks, David / dhildenb