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 1Jxs4fxV 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insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h >> index d18e5c332cb9..03e3c69fc427 100644 >> --- a/arch/x86/include/asm/page.h >> +++ b/arch/x86/include/asm/page.h >> @@ -28,6 +28,12 @@ static inline void clear_user_page(void *page, unsigned long vaddr, >> clear_page(page); >> } >> >> +static inline void clear_user_pages(void *page, unsigned long vaddr, >> + struct page *pg, unsigned int nsubpages) >> +{ >> + clear_pages(page, nsubpages); >> +} > > This seems dodgy, clear_user* has slightly different semantics. It needs > the access_ok() and stac/clac thing on at the very least. That can't be right. On x86, clear_user_page(), copy_user_page() (and now the multi-page versions) only write to kernel maps of user pages. That's why they can skip the access_ok(), stac/clac or uacess exception handling. >From core-api/cachetlb.rst: ``void copy_user_page(void *to, void *from, unsigned long addr, struct page *page)`` ``void clear_user_page(void *to, unsigned long addr, struct page *page)`` These two routines store data in user anonymous or COW pages. It allows a port to efficiently avoid D-cache alias issues between userspace and the kernel. For example, a port may temporarily map 'from' and 'to' to kernel virtual addresses during the copy. The virtual address for these two pages is chosen in such a way that the kernel load/store instructions happen to virtual addresses which are of the same "color" as the user mapping of the page. Sparc64 for example, uses this technique. The 'addr' parameter tells the virtual address where the user will ultimately have this page mapped, and the 'page' parameter gives a pointer to the struct page of the target. The naming OTOH does seems dodgy. Especially because as you say it suggests semantics similar to clear_user() etc. On x86, I think it is definitely a mistake for clear_huge_page() to be calling clear_user_page*() (especially given that it is getting the kernel map.) Will fix that. Even for non-x86, I see just two users in common code: highmem.h: copy_user_highpage(), clear_user_highpage() fs/dax.c: copy_cow_page_dax() All of them do a kmap_atomic() so there's really no "may" as documented above: For example, a port may temporarily map 'from' and 'to' to kernel virtual addresses during the copy. The virtual address Maybe a name change is warranted, if nothing else? >> + >> static inline void copy_user_page(void *to, void *from, unsigned long vaddr, >> struct page *topage) >> { >> diff --git a/arch/x86/include/asm/page_32.h b/arch/x86/include/asm/page_32.h >> index 580d71aca65a..3523d1150cfc 100644 >> --- a/arch/x86/include/asm/page_32.h >> +++ b/arch/x86/include/asm/page_32.h >> @@ -22,6 +22,12 @@ static inline void clear_page(void *page) >> memset(page, 0, PAGE_SIZE); >> } >> >> +static inline void clear_pages(void *page, unsigned int nsubpages) >> +{ >> + for (int i = 0; i < nsubpages; i++) >> + clear_page(page + i * PAGE_SIZE); > > cond_resched() ? Missed that. Thanks. Will fix. -- ankur