search for: kmap_atomic

kmap_atomic() is deprecated in favor of kmap_local_page() since commit f3ba3c710ac5 ("mm/highmem: Provide kmap_local*"). With kmap_local_page() the mappings are per thread, CPU local, can take page-faults, and can be called from any context (including interrupts). Furthermore, the tasks can be preem...

...kunmap(struct page *page) +{ + might_sleep(); + if (!PageHighMem(page)) + return; + kunmap_high(page); +} + +static inline struct page *kmap_to_page(void *addr) +{ + return __kmap_to_page(addr); +} + +static inline void kmap_flush_unused(void) +{ + __kmap_flush_unused(); +} + +static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) +{ + preempt_disable(); + pagefault_disable(); + return __kmap_local_page_prot(page, prot); +} + +static inline void *kmap_atomic(struct page *page) +{ + return kmap_atomic_prot(page, kmap_prot); +} + +static inline void *kmap_atomic_pfn(unsigned long pfn) +{...

The kmap_atomic* interfaces in all architectures are pretty much the same except for post map operations (flush) and pre- and post unmap operations. Provide a generic variant for that. Signed-off-by: Thomas Gleixner <tglx at linutronix.de> Cc: Andrew Morton <akpm at linux-foundation.org> Cc: linux-mm...

...s obviously slow, but highmem is slow anyway. The kmap_local.*() functions can be invoked from both preemptible and atomic context. kmap local sections disable migration to keep the resulting virtual mapping address correct, but disable neither pagefaults nor preemption. A wholesale conversion of kmap_atomic to be fully preemptible is not possible because some of the usage sites might rely on the preemption disable for serialization or on the implicit pagefault disable. Needs to be done on a case by case basis. Signed-off-by: Thomas Gleixner <tglx at linutronix.de> --- V3: Move migrate disable i...

On Thu, Mar 16, 2023 at 10:13:39AM +0100, Fabio M. De Francesco wrote: >On gioved? 2 marzo 2023 12:34:16 CET Stefano Garzarella wrote: >> kmap_atomic() is deprecated in favor of kmap_local_page(). >> >> With kmap_local_page() the mappings are per thread, CPU local, can take >> page-faults, and can be called from any context (including interrupts). >> Furthermore, the tasks can be preempted and, when they are scheduled to...

...7 ----- 2 files changed, 5 insertions(+), 65 deletions(-) --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -86,31 +86,16 @@ static inline void kunmap(struct page *p * be used in IRQ contexts, so in some (very limited) cases we need * it. */ - -#ifndef CONFIG_KMAP_LOCAL -void *kmap_atomic_high_prot(struct page *page, pgprot_t prot); -void kunmap_atomic_high(void *kvaddr); - static inline void *kmap_atomic_prot(struct page *page, pgprot_t prot) { preempt_disable(); pagefault_disable(); - if (!PageHighMem(page)) - return page_address(page); - return kmap_atomic_high_prot(page,...

There is no reason to disable pagefaults and preemption as a side effect of kmap_atomic_prot(). Use kmap_local_page_prot() instead and document the reasoning for the mapping usage with the given pgprot. Remove the NULL pointer check for the map. These functions return a valid address for valid pages and the return was bogus anyway as it would have left preemption and pagefaults disa...

...arch/i386/mm/highmem-xen.c =================================================================== --- head-2008-10-24.orig/arch/i386/mm/highmem-xen.c 2008-10-27 11:56:39.000000000 +0100 +++ head-2008-10-24/arch/i386/mm/highmem-xen.c 2008-10-27 11:56:59.000000000 +0100 @@ -151,9 +151,56 @@ struct page *kmap_atomic_to_page(void *p return pte_page(*pte); } +void clear_highpage(struct page *page) +{ + void *kaddr; + + if (likely(xen_feature(XENFEAT_highmem_assist)) + && PageHighMem(page)) { + struct mmuext_op meo; + + meo.cmd = MMUEXT_CLEAR_PAGE; + meo.arg1.mfn = pfn_to_mfn(page_to_pfn(page)...

There is no reason to disable pagefaults and preemption as a side effect of kmap_atomic_prot(). Use kmap_local_page_prot() instead and document the reasoning for the mapping usage with the given pgprot. Remove the NULL pointer check for the map. These functions return a valid address for valid pages and the return was bogus anyway as it would have left preemption and pagefaults disa...

Following up to the discussion in: https://lore.kernel.org/r/20200914204209.256266093 at linutronix.de and the second version of this: https://lore.kernel.org/r/20201029221806.189523375 at linutronix.de this series provides a preemptible variant of kmap_atomic & related interfaces. This is achieved by: - Removing the RT dependency from migrate_disable/enable() - Consolidating all kmap atomic implementations in generic code including a useful version of the CONFIG_DEBUG_HIGHMEM which provides guard pages between the individual maps instead...

Following up to the discussion in: https://lore.kernel.org/r/20200914204209.256266093 at linutronix.de and the second version of this: https://lore.kernel.org/r/20201029221806.189523375 at linutronix.de this series provides a preemptible variant of kmap_atomic & related interfaces. This is achieved by: - Removing the RT dependency from migrate_disable/enable() - Consolidating all kmap atomic implementations in generic code including a useful version of the CONFIG_DEBUG_HIGHMEM which provides guard pages between the individual maps instead...

Following up to the discussion in: https://lore.kernel.org/r/20200914204209.256266093 at linutronix.de and the second version of this: https://lore.kernel.org/r/20201029221806.189523375 at linutronix.de this series provides a preemptible variant of kmap_atomic & related interfaces. This is achieved by: - Removing the RT dependency from migrate_disable/enable() - Consolidating all kmap atomic implementations in generic code including a useful version of the CONFIG_DEBUG_HIGHMEM which provides guard pages between the individual maps instead...

Don't implement native_kmap_atomic_pte for !HIGHPTE case; it is never needed, never called, and leaving it in is just plain confusing. Making it isolated to the config where it is used may help find bugs. Signed-off-by: Zachary Amsden <zach@vmware.com> diff -r 5c03805411a6 arch/i386/kernel/paravirt.c --- a/arch/i386/kernel/...

Don't implement native_kmap_atomic_pte for !HIGHPTE case; it is never needed, never called, and leaving it in is just plain confusing. Making it isolated to the config where it is used may help find bugs. Signed-off-by: Zachary Amsden <zach@vmware.com> diff -r 5c03805411a6 arch/i386/kernel/paravirt.c --- a/arch/i386/kernel/...

...e's just one page (or a few pages) in each vmap there's no need of vmap, the linearity vmap provides doesn't pay off in such case. So likely there's further room for improvement here that you can achieve in the current series by just dropping vmap/vunmap. You can just use kmap (or kmap_atomic if you're in preemptible section, should work from bh/irq). In short the mmu notifier to invalidate only sets a "struct page * userringpage" pointer to NULL without calls to vunmap. In all cases immediately after gup_fast returns you can always call put_page immediately (which expla...

...e's just one page (or a few pages) in each vmap there's no need of vmap, the linearity vmap provides doesn't pay off in such case. So likely there's further room for improvement here that you can achieve in the current series by just dropping vmap/vunmap. You can just use kmap (or kmap_atomic if you're in preemptible section, should work from bh/irq). In short the mmu notifier to invalidate only sets a "struct page * userringpage" pointer to NULL without calls to vunmap. In all cases immediately after gup_fast returns you can always call put_page immediately (which expla...

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has arch_futex_atomic_op_inuser() which could be used for setting a bit to user. Note ther...

Vhost log dirty pages directly to a userspace bitmap through GUP and kmap_atomic() since kernel doesn't have a set_bit_to_user() helper. This will cause issues for the arch that has virtually tagged caches. The way to fix is to keep using userspace virtual address. Fortunately, futex has arch_futex_atomic_op_inuser() which could be used for setting a bit to user. Note ther...

On Tue, Mar 12, 2019 at 03:02:54PM -0700, James Bottomley wrote: > I'm sure there must be workarounds elsewhere in the other arch code > otherwise things like this, which appear all over drivers/, wouldn't > work: > > drivers/scsi/isci/request.c:1430 > > kaddr = kmap_atomic(page); > memcpy(kaddr + sg->offset, src_addr, copy_len); > kunmap_atomic(kaddr); > Are you sure "page" is an userland page with an alias address? sg->page_link = (unsigned long)virt_to_page(addr); page_link seems to point to kernel memory. I found an apparent soluti...

Do you disable interrupts when lazy_mmu is active? Otherwise, it seems to me that drivers will have problems using kmap_atomic() within an interrupt routine... J