| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <11f86b1c-a12e-4cd3-8b4e-a8a34c64fbf1@arm.com>
Date: Wed, 30 Apr 2025 11:12:45 +0530
From: Dev Jain <dev.jain@....com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org,
ryan.roberts@....com, david@...hat.com, willy@...radead.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org, catalin.marinas@....com,
will@...nel.org, Liam.Howlett@...cle.com, vbabka@...e.cz, jannh@...gle.com,
anshuman.khandual@....com, peterx@...hat.com, joey.gouly@....com,
ioworker0@...il.com, baohua@...nel.org, kevin.brodsky@....com,
quic_zhenhuah@...cinc.com, christophe.leroy@...roup.eu,
yangyicong@...ilicon.com, linux-arm-kernel@...ts.infradead.org,
namit@...are.com, hughd@...gle.com, yang@...amperecomputing.com,
ziy@...dia.com
Subject: Re: [PATCH v2 0/7] Optimize mprotect for large folios
On 29/04/25 4:11 pm, Lorenzo Stoakes wrote:
> FWIW can confirm the same thing. Lance's fixes sort most of it out, but I also
> get this error:
>
> mm/mprotect.c: In function ‘can_change_ptes_writable’:
> mm/mprotect.c:46:22: error: unused variable ‘page’ [-Werror=unused-variable]
> 46 | struct page *page;
> | ^~~~
>
> So you also need to remove this unused variable at the stop of
> can_change_ptes_writable().
Strange that my build didn't catch this.
>
> Cheers, Lorenzo
>
> On Tue, Apr 29, 2025 at 02:32:59PM +0530, Dev Jain wrote:
>>
>>
>> On 29/04/25 12:36 pm, Lance Yang wrote:
>>> Hey Dev,
>>>
>>> Hmm... I also hit the same compilation errors:
>>>
>>> In file included from ./include/linux/kasan.h:37,
>>> from ./include/linux/slab.h:260,
>>> from ./include/linux/crypto.h:19,
>>> from arch/x86/kernel/asm-offsets.c:9:
>>> ./include/linux/pgtable.h: In function ‘modify_prot_start_ptes’:
>>> ./include/linux/pgtable.h:905:15: error: implicit declaration of
>>> function ‘ptep_modify_prot_start’
>>> [-Werror=implicit-function-declaration]
>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:905:15: error: incompatible types when
>>> assigning to type ‘pte_t’ from type ‘int’
>>> ./include/linux/pgtable.h:909:27: error: incompatible types when
>>> assigning to type ‘pte_t’ from type ‘int’
>>> 909 | tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h: In function ‘modify_prot_commit_ptes’:
>>> ./include/linux/pgtable.h:925:17: error: implicit declaration of
>>> function ‘ptep_modify_prot_commit’
>>> [-Werror=implicit-function-declaration]
>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>> old_pte, pte);
>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h: At top level:
>>> ./include/linux/pgtable.h:1360:21: error: conflicting types for
>>> ‘ptep_modify_prot_start’; have ‘pte_t(struct vm_area_struct *, long
>>> unsigned int, pte_t *)’
>>> 1360 | static inline pte_t ptep_modify_prot_start(struct
>>> vm_area_struct *vma,
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:905:15: note: previous implicit declaration of
>>> ‘ptep_modify_prot_start’ with type ‘int()’
>>> 905 | pte = ptep_modify_prot_start(vma, addr, ptep);
>>> | ^~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:1371:20: warning: conflicting types for
>>> ‘ptep_modify_prot_commit’; have ‘void(struct vm_area_struct *, long
>>> unsigned int, pte_t *, pte_t, pte_t)’
>>> 1371 | static inline void ptep_modify_prot_commit(struct
>>> vm_area_struct *vma,
>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>> ./include/linux/pgtable.h:1371:20: error: static declaration of
>>> ‘ptep_modify_prot_commit’ follows non-static declaration
>>> ./include/linux/pgtable.h:925:17: note: previous implicit declaration of
>>> ‘ptep_modify_prot_commit’ with type ‘void(struct vm_area_struct *, long
>>> unsigned int, pte_t *, pte_t, pte_t)’
>>> 925 | ptep_modify_prot_commit(vma, addr, ptep,
>>> old_pte, pte);
>>> | ^~~~~~~~~~~~~~~~~~~~~~~
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> libstring.o
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> libctype.o
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> str_error_r.o
>>> CC /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> librbtree.o
>>> cc1: some warnings being treated as errors
>>> make[2]: *** [scripts/Makefile.build:98: arch/x86/kernel/asm-offsets.s]
>>> Error 1
>>> make[1]: *** [/home/runner/work/mm-test-robot/mm-test-robot/linux/
>>> Makefile:1280: prepare0] Error 2
>>> make[1]: *** Waiting for unfinished jobs....
>>> LD /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/objtool/
>>> objtool-in.o
>>> LINK /home/runner/work/mm-test-robot/mm-test-robot/linux/tools/
>>> objtool/objtool
>>> make: *** [Makefile:248: __sub-make] Error 2
>>>
>>> Well, modify_prot_start_ptes() calls ptep_modify_prot_start(), but x86
>>> does not define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION. To avoid
>>> implicit declaration errors, the architecture-independent
>>> ptep_modify_prot_start() must be defined before modify_prot_start_ptes().
>>>
>>> With the changes below, things work correctly now ;)
>>
>> Ah thanks! My bad :(
>>
>>>
>>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>>> index 10cdb87ccecf..d9d6c49bb914 100644
>>> --- a/include/linux/pgtable.h
>>> +++ b/include/linux/pgtable.h
>>> @@ -895,44 +895,6 @@ static inline void wrprotect_ptes(struct mm_struct
>>> *mm, unsigned long addr,
>>> }
>>> #endif
>>>
>>> -/* See the comment for ptep_modify_prot_start */
>>> -#ifndef modify_prot_start_ptes
>>> -static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
>>> - unsigned long addr, pte_t *ptep, unsigned int nr)
>>> -{
>>> - pte_t pte, tmp_pte;
>>> -
>>> - pte = ptep_modify_prot_start(vma, addr, ptep);
>>> - while (--nr) {
>>> - ptep++;
>>> - addr += PAGE_SIZE;
>>> - tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>> - if (pte_dirty(tmp_pte))
>>> - pte = pte_mkdirty(pte);
>>> - if (pte_young(tmp_pte))
>>> - pte = pte_mkyoung(pte);
>>> - }
>>> - return pte;
>>> -}
>>> -#endif
>>> -
>>> -/* See the comment for ptep_modify_prot_commit */
>>> -#ifndef modify_prot_commit_ptes
>>> -static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
>>> unsigned long addr,
>>> - pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>> -{
>>> - for (;;) {
>>> - ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>> - if (--nr == 0)
>>> - break;
>>> - ptep++;
>>> - addr += PAGE_SIZE;
>>> - old_pte = pte_next_pfn(old_pte);
>>> - pte = pte_next_pfn(pte);
>>> - }
>>> -}
>>> -#endif
>>> -
>>> /*
>>> * On some architectures hardware does not set page access bit when
>>> accessing
>>> * memory page, it is responsibility of software setting this bit. It
>>> brings
>>> @@ -1375,6 +1337,45 @@ static inline void ptep_modify_prot_commit(struct
>>> vm_area_struct *vma,
>>> __ptep_modify_prot_commit(vma, addr, ptep, pte);
>>> }
>>> #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
>>> +
>>> +/* See the comment for ptep_modify_prot_start */
>>> +#ifndef modify_prot_start_ptes
>>> +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
>>> + unsigned long addr, pte_t *ptep, unsigned int nr)
>>> +{
>>> + pte_t pte, tmp_pte;
>>> +
>>> + pte = ptep_modify_prot_start(vma, addr, ptep);
>>> + while (--nr) {
>>> + ptep++;
>>> + addr += PAGE_SIZE;
>>> + tmp_pte = ptep_modify_prot_start(vma, addr, ptep);
>>> + if (pte_dirty(tmp_pte))
>>> + pte = pte_mkdirty(pte);
>>> + if (pte_young(tmp_pte))
>>> + pte = pte_mkyoung(pte);
>>> + }
>>> + return pte;
>>> +}
>>> +#endif
>>> +
>>> +/* See the comment for ptep_modify_prot_commit */
>>> +#ifndef modify_prot_commit_ptes
>>> +static inline void modify_prot_commit_ptes(struct vm_area_struct *vma,
>>> unsigned long addr,
>>> + pte_t *ptep, pte_t old_pte, pte_t pte, unsigned int nr)
>>> +{
>>> + for (;;) {
>>> + ptep_modify_prot_commit(vma, addr, ptep, old_pte, pte);
>>> + if (--nr == 0)
>>> + break;
>>> + ptep++;
>>> + addr += PAGE_SIZE;
>>> + old_pte = pte_next_pfn(old_pte);
>>> + pte = pte_next_pfn(pte);
>>> + }
>>> +}
>>> +#endif
>>> +
>>> #endif /* CONFIG_MMU */
>>>
>>> /*
>>> --
>>>
>>> Thanks,
>>> Lance
>>>
>>> On 2025/4/29 13:23, Dev Jain wrote:
>>>> This patchset optimizes the mprotect() system call for large folios
>>>> by PTE-batching.
>>>>
>>>> We use the following test cases to measure performance, mprotect()'ing
>>>> the mapped memory to read-only then read-write 40 times:
>>>>
>>>> Test case 1: Mapping 1G of memory, touching it to get PMD-THPs, then
>>>> pte-mapping those THPs
>>>> Test case 2: Mapping 1G of memory with 64K mTHPs
>>>> Test case 3: Mapping 1G of memory with 4K pages
>>>>
>>>> Average execution time on arm64, Apple M3:
>>>> Before the patchset:
>>>> T1: 7.9 seconds T2: 7.9 seconds T3: 4.2 seconds
>>>>
>>>> After the patchset:
>>>> T1: 2.1 seconds T2: 2.2 seconds T3: 4.2 seconds
>>>>
>>>> Observing T1/T2 and T3 before the patchset, we also remove the regression
>>>> introduced by ptep_get() on a contpte block. And, for large folios we get
>>>> an almost 74% performance improvement.
>>>>
>>>> v1->v2:
>>>> - Rebase onto mm-unstable (6ebffe676fcf: util_macros.h: make the
>>>> header more resilient)
>>>> - Abridge the anon-exclusive condition (Lance Yang)
>>>>
>>>> Dev Jain (7):
>>>> mm: Refactor code in mprotect
>>>> mm: Optimize mprotect() by batch-skipping PTEs
>>>> mm: Add batched versions of ptep_modify_prot_start/commit
>>>> arm64: Add batched version of ptep_modify_prot_start
>>>> arm64: Add batched version of ptep_modify_prot_commit
>>>> mm: Batch around can_change_pte_writable()
>>>> mm: Optimize mprotect() through PTE-batching
>>>>
>>>> arch/arm64/include/asm/pgtable.h | 10 ++
>>>> arch/arm64/mm/mmu.c | 21 +++-
>>>> include/linux/mm.h | 4 +-
>>>> include/linux/pgtable.h | 42 ++++++++
>>>> mm/gup.c | 2 +-
>>>> mm/huge_memory.c | 4 +-
>>>> mm/memory.c | 6 +-
>>>> mm/mprotect.c | 165 ++++++++++++++++++++-----------
>>>> mm/pgtable-generic.c | 16 ++-
>>>> 9 files changed, 198 insertions(+), 72 deletions(-)
>>>>
>>>
>>
Powered by blists - more mailing lists