search for: flush_dcache_pag

...nything different that you worry? > > If caches have virtual tags then kernel and userspace view of memory > might not be automatically in sync if they access memory > through different virtual addresses. You need to do things like > flush_cache_page, probably multiple times. "flush_dcache_page()"

...nything different that you worry? > > If caches have virtual tags then kernel and userspace view of memory > might not be automatically in sync if they access memory > through different virtual addresses. You need to do things like > flush_cache_page, probably multiple times. "flush_dcache_page()"

...al tags then kernel and userspace view of >>>> memory >>>> might not be automatically in sync if they access memory >>>> through different virtual addresses. You need to do things like >>>> flush_cache_page, probably multiple times. >>> "flush_dcache_page()" >> >> I get this. Then I think the current set_bit_to_user() is suspicious, >> we >> probably miss a flush_dcache_page() there: >> >> >> static int set_bit_to_user(int nr, void __user *addr) >> { >> unsigned long log = (unsign...

...> If caches have virtual tags then kernel and userspace view of memory > > > might not be automatically in sync if they access memory > > > through different virtual addresses. You need to do things like > > > flush_cache_page, probably multiple times. > > "flush_dcache_page()" > > > I get this. Then I think the current set_bit_to_user() is suspicious, we > probably miss a flush_dcache_page() there: > > > static int set_bit_to_user(int nr, void __user *addr) > { > ??????? unsigned long log = (unsigned long)addr; > ??????? struct...

...> If caches have virtual tags then kernel and userspace view of memory > > > might not be automatically in sync if they access memory > > > through different virtual addresses. You need to do things like > > > flush_cache_page, probably multiple times. > > "flush_dcache_page()" > > > I get this. Then I think the current set_bit_to_user() is suspicious, we > probably miss a flush_dcache_page() there: > > > static int set_bit_to_user(int nr, void __user *addr) > { > ??????? unsigned long log = (unsigned long)addr; > ??????? struct...

...-git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 351af88231ad..34a1cedbc5ba 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1711,6 +1711,7 @@ static int set_bit_to_user(int nr, void __user *addr) base = kmap_atomic(page); set_bit(bit, base); kunmap_atomic(base); + flush_dcache_page(page); set_page_dirty_lock(page); put_page(page); return 0; -- 2.19.1

...-git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index 351af88231ad..34a1cedbc5ba 100644 --- a/drivers/vhost/vhost.c +++ b/drivers/vhost/vhost.c @@ -1711,6 +1711,7 @@ static int set_bit_to_user(int nr, void __user *addr) base = kmap_atomic(page); set_bit(bit, base); kunmap_atomic(base); + flush_dcache_page(page); set_page_dirty_lock(page); put_page(page); return 0; -- 2.19.1

...; > See James's reply - I stand corrected we do kunmap so no need to > > flush. > > Well, I said that's what we do on Parisc. The cachetlb document > definitely says if you alter the data between kmap and kunmap you are > responsible for the flush. It's just that flush_dcache_page() is a no- > op on x86 so they never remember to add it and since it will crash > parisc if you get it wrong we finally gave up trying to make them. > > But that's the point: it is a no-op on your favourite architecture so > it costs you nothing to add it. Yes, the fact Parisc...

On Tue, Mar 12, 2019 at 02:19:15PM -0700, James Bottomley wrote: > I mean in the sequence > > flush_dcache_page(page); > flush_dcache_page(page); > > The first flush_dcache_page did all the work and the second it a > tightly pipelined no-op. That's what I mean by there not really being > a double hit. Ok I wasn't sure it was clear there was a double (profiling) hit on that function...

...or all architectures > > that need cache flushing and then remove the explicit flushing in > > the callers.. > > Well, it's already done on parisc ... I can help with this if we agree > it's the best way forward. It's really only architectures that > implement flush_dcache_page that would need modifying. > > It may also improve performance because some kmap/use/flush/kunmap > sequences have flush_dcache_page() instead of > flush_kernel_dcache_page() and the former is hugely expensive and > usually unnecessary because GUP already flushed all the user alias...

...ge, i, offset, count); - pagefault_enable(); + if (unlikely(iov_iter_fault_in_readable(i, count))) + return -EFAULT; + + /* Copy data from userspace to the current page */ + copied = iov_iter_copy_from_user(page, i, offset, count); /* Flush processor''s dcache for this page */ flush_dcache_page(page); @@ -978,15 +974,6 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb, if (ret) goto out; - /* - * fault pages before locking them in prepare_pages - * to avoid recursive lock - */ - if (unlikely(iov_iter_fault_in_readable(&i, write_bytes))) { -...

...ent that you worry? >> If caches have virtual tags then kernel and userspace view of memory >> might not be automatically in sync if they access memory >> through different virtual addresses. You need to do things like >> flush_cache_page, probably multiple times. > "flush_dcache_page()" I get this. Then I think the current set_bit_to_user() is suspicious, we probably miss a flush_dcache_page() there: static int set_bit_to_user(int nr, void __user *addr) { ??????? unsigned long log = (unsigned long)addr; ??????? struct page *page; ??????? void *base; ??????? int b...

...caches have virtual tags then kernel and userspace view of memory >>>> might not be automatically in sync if they access memory >>>> through different virtual addresses. You need to do things like >>>> flush_cache_page, probably multiple times. >>> "flush_dcache_page()" >> >> I get this. Then I think the current set_bit_to_user() is suspicious, we >> probably miss a flush_dcache_page() there: >> >> >> static int set_bit_to_user(int nr, void __user *addr) >> { >> ??????? unsigned long log = (unsigned long)ad...

...host/vhost.c > index 351af88231ad..34a1cedbc5ba 100644 > --- a/drivers/vhost/vhost.c > +++ b/drivers/vhost/vhost.c > @@ -1711,6 +1711,7 @@ static int set_bit_to_user(int nr, void __user *addr) > base = kmap_atomic(page); > set_bit(bit, base); > kunmap_atomic(base); > + flush_dcache_page(page); > set_page_dirty_lock(page); > put_page(page); > return 0; Ignoring the question of whether this actually helps, I doubt flush_dcache_page is appropriate here. Pls take a look at Documentation/core-api/cachetlb.rst as well as the actual implementation. I think you meant fl...

...ot bother zeroing the page. Invalidate + * it instead so that writeback does not get confused + * put page & buffer dirty bits into inconsistent + * state. + */ + block_invalidate_folio(page_folio(wc->w_target_page), + 0, PAGE_SIZE); + } } if (wc->w_target_page) flush_dcache_page(wc->w_target_page); -- 2.35.3

...the cache flushing on copy_to_user_page and copy_user_page, not on kunmap. #define copy_user_page(to,from,vaddr,pg) __cpu_copy_user_page(to, from, vaddr) void __cpu_copy_user_page(void *kto, const void *kfrom, unsigned long vaddr) { struct page *page = virt_to_page(kto); copy_page(kto, kfrom); flush_dcache_page(page); } #define copy_user_page(to, from, vaddr, page) \ do { copy_page(to, from); \ sparc_flush_page_to_ram(page); \ } while (0) And they do nothing on kunmap: static inline void kunmap(struct page *page) { BUG_ON(in_interrupt()); if (!PageHighMem(page)) return; kunmap_high(page); } v...

...asm-ia64/page.h Linus Torvalds 2005-04-16 68 /* ^1da177e4c3f41 include/asm-ia64/page.h Linus Torvalds 2005-04-16 69 * clear_user_page() and copy_user_page() can't be inline functions because ^1da177e4c3f41 include/asm-ia64/page.h Linus Torvalds 2005-04-16 70 * flush_dcache_page() can't be defined until later... ^1da177e4c3f41 include/asm-ia64/page.h Linus Torvalds 2005-04-16 71 */ ^1da177e4c3f41 include/asm-ia64/page.h Linus Torvalds 2005-04-16 72 #define clear_user_page(addr, vaddr, page) \ ^1da177e4c3f41 include/asm-ia64/page.h Linus Tor...

...ot bother zeroing the page. Invalidate + * it instead so that writeback does not get confused + * put page & buffer dirty bits into inconsistent + * state. + */ + block_invalidate_folio(page_folio(wc->w_target_page), + 0, PAGE_SIZE); + } } if (wc->w_target_page) flush_dcache_page(wc->w_target_page);

...ot bother zeroing the page. Invalidate + * it instead so that writeback does not get confused + * put page & buffer dirty bits into inconsistent + * state. + */ + block_invalidate_folio(page_folio(wc->w_target_page), + 0, PAGE_SIZE); + } } if (wc->w_target_page) flush_dcache_page(wc->w_target_page);

...mem += vec.bv_len; + transfered += vec.bv_len; } bio_endio(bio, 0); } diff --git a/block/blk-core.c b/block/blk-core.c index 5c2ab2c..5da8e90 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2746,10 +2746,10 @@ void blk_rq_bio_prep(struct request_queue *q, struct request *rq, void rq_flush_dcache_pages(struct request *rq) { struct req_iterator iter; - struct bio_vec *bvec; + struct bio_vec bvec; rq_for_each_segment(bvec, rq, iter) - flush_dcache_page(bvec->bv_page); + flush_dcache_page(bvec.bv_page); } EXPORT_SYMBOL_GPL(rq_flush_dcache_pages); #endif diff --git a/block/blk-merge....