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linux/arch/arm/include/asm/highmem.h

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[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-15 20:44:55 +00:00
#ifndef _ASM_HIGHMEM_H
#define _ASM_HIGHMEM_H
#include <asm/kmap_types.h>
#define PKMAP_BASE (PAGE_OFFSET - PMD_SIZE)
#define LAST_PKMAP PTRS_PER_PTE
#define LAST_PKMAP_MASK (LAST_PKMAP - 1)
#define PKMAP_NR(virt) (((virt) - PKMAP_BASE) >> PAGE_SHIFT)
#define PKMAP_ADDR(nr) (PKMAP_BASE + ((nr) << PAGE_SHIFT))
#define kmap_prot PAGE_KERNEL
ARM: 6007/1: fix highmem with VIPT cache and DMA The VIVT cache of a highmem page is always flushed before the page is unmapped. This cache flush is explicit through flush_cache_kmaps() in flush_all_zero_pkmaps(), or through __cpuc_flush_dcache_area() in kunmap_atomic(). There is also an implicit flush of those highmem pages that were part of a process that just terminated making those pages free as the whole VIVT cache has to be flushed on every task switch. Hence unmapped highmem pages need no cache maintenance in that case. However unmapped pages may still be cached with a VIPT cache because the cache is tagged with physical addresses. There is no need for a whole cache flush during task switching for that reason, and despite the explicit cache flushes in flush_all_zero_pkmaps() and kunmap_atomic(), some highmem pages that were mapped in user space end up still cached even when they become unmapped. So, we do have to perform cache maintenance on those unmapped highmem pages in the context of DMA when using a VIPT cache. Unfortunately, it is not possible to perform that cache maintenance using physical addresses as all the L1 cache maintenance coprocessor functions accept virtual addresses only. Therefore we have no choice but to set up a temporary virtual mapping for that purpose. And of course the explicit cache flushing when unmapping a highmem page on a system with a VIPT cache now can go, which should increase performance. While at it, because the code in __flush_dcache_page() has to be modified anyway, let's also make sure the mapped highmem pages are pinned with kmap_high_get() for the duration of the cache maintenance operation. Because kunmap() does unmap highmem pages lazily, it was reported by Gary King <GKing@nvidia.com> that those pages ended up being unmapped during cache maintenance on SMP causing segmentation faults. Signed-off-by: Nicolas Pitre <nico@marvell.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-03-29 20:46:02 +00:00
#define flush_cache_kmaps() \
do { \
if (cache_is_vivt()) \
flush_cache_all(); \
} while (0)
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-15 20:44:55 +00:00
extern pte_t *pkmap_page_table;
ARM: 6639/1: allow highmem on SMP platforms without h/w TLB ops broadcast In commit e616c591405c168f6dc3dfd1221e105adfe49b8d, highmem support was deactivated for SMP platforms without hardware TLB ops broadcast because usage of kmap_high_get() requires that IRQs be disabled when kmap_lock is locked which is incompatible with the IPI mechanism used by the software TLB ops broadcast invoked through flush_all_zero_pkmaps(). The reason for kmap_high_get() is to ensure that the currently kmap'd page usage count does not decrease to zero while we're using its existing virtual mapping in an atomic context. With a VIVT cache this is essential to do due to cache coherency issues, but with a VIPT cache this is only an optimization so not to pay the price of establishing a second mapping if an existing one can be used. However, on VIPT platforms without hardware TLB maintenance we can give up on that optimization in order to be able to use highmem. From ARMv7 onwards the TLB ops are broadcasted in hardware, so let's disable ARCH_NEEDS_KMAP_HIGH_GET only when CONFIG_SMP and CONFIG_CPU_TLB_V6 are defined. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org> Tested-by: Saeed Bishara <saeed.bishara@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-01-25 20:35:38 +00:00
extern void *kmap_high(struct page *page);
extern void kunmap_high(struct page *page);
/*
* The reason for kmap_high_get() is to ensure that the currently kmap'd
* page usage count does not decrease to zero while we're using its
* existing virtual mapping in an atomic context. With a VIVT cache this
* is essential to do, but with a VIPT cache this is only an optimization
* so not to pay the price of establishing a second mapping if an existing
* one can be used. However, on platforms without hardware TLB maintenance
* broadcast, we simply cannot use ARCH_NEEDS_KMAP_HIGH_GET at all since
* the locking involved must also disable IRQs which is incompatible with
* the IPI mechanism used by global TLB operations.
*/
[ARM] introduce dma_cache_maint_page() This is a helper to be used by the DMA mapping API to handle cache maintenance for memory identified by a page structure instead of a virtual address. Those pages may or may not be highmem pages, and when they're highmem pages, they may or may not be virtually mapped. When they're not mapped then there is no L1 cache to worry about. But even in that case the L2 cache must be processed since unmapped highmem pages can still be L2 cached. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2009-03-13 02:52:09 +00:00
#define ARCH_NEEDS_KMAP_HIGH_GET
ARM: 6639/1: allow highmem on SMP platforms without h/w TLB ops broadcast In commit e616c591405c168f6dc3dfd1221e105adfe49b8d, highmem support was deactivated for SMP platforms without hardware TLB ops broadcast because usage of kmap_high_get() requires that IRQs be disabled when kmap_lock is locked which is incompatible with the IPI mechanism used by the software TLB ops broadcast invoked through flush_all_zero_pkmaps(). The reason for kmap_high_get() is to ensure that the currently kmap'd page usage count does not decrease to zero while we're using its existing virtual mapping in an atomic context. With a VIVT cache this is essential to do due to cache coherency issues, but with a VIPT cache this is only an optimization so not to pay the price of establishing a second mapping if an existing one can be used. However, on VIPT platforms without hardware TLB maintenance we can give up on that optimization in order to be able to use highmem. From ARMv7 onwards the TLB ops are broadcasted in hardware, so let's disable ARCH_NEEDS_KMAP_HIGH_GET only when CONFIG_SMP and CONFIG_CPU_TLB_V6 are defined. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org> Tested-by: Saeed Bishara <saeed.bishara@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-01-25 20:35:38 +00:00
#if defined(CONFIG_SMP) && defined(CONFIG_CPU_TLB_V6)
#undef ARCH_NEEDS_KMAP_HIGH_GET
#if defined(CONFIG_HIGHMEM) && defined(CONFIG_CPU_CACHE_VIVT)
#error "The sum of features in your kernel config cannot be supported together"
#endif
#endif
[ARM] introduce dma_cache_maint_page() This is a helper to be used by the DMA mapping API to handle cache maintenance for memory identified by a page structure instead of a virtual address. Those pages may or may not be highmem pages, and when they're highmem pages, they may or may not be virtually mapped. When they're not mapped then there is no L1 cache to worry about. But even in that case the L2 cache must be processed since unmapped highmem pages can still be L2 cached. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2009-03-13 02:52:09 +00:00
ARM: 6639/1: allow highmem on SMP platforms without h/w TLB ops broadcast In commit e616c591405c168f6dc3dfd1221e105adfe49b8d, highmem support was deactivated for SMP platforms without hardware TLB ops broadcast because usage of kmap_high_get() requires that IRQs be disabled when kmap_lock is locked which is incompatible with the IPI mechanism used by the software TLB ops broadcast invoked through flush_all_zero_pkmaps(). The reason for kmap_high_get() is to ensure that the currently kmap'd page usage count does not decrease to zero while we're using its existing virtual mapping in an atomic context. With a VIVT cache this is essential to do due to cache coherency issues, but with a VIPT cache this is only an optimization so not to pay the price of establishing a second mapping if an existing one can be used. However, on VIPT platforms without hardware TLB maintenance we can give up on that optimization in order to be able to use highmem. From ARMv7 onwards the TLB ops are broadcasted in hardware, so let's disable ARCH_NEEDS_KMAP_HIGH_GET only when CONFIG_SMP and CONFIG_CPU_TLB_V6 are defined. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org> Tested-by: Saeed Bishara <saeed.bishara@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-01-25 20:35:38 +00:00
#ifdef ARCH_NEEDS_KMAP_HIGH_GET
[ARM] introduce dma_cache_maint_page() This is a helper to be used by the DMA mapping API to handle cache maintenance for memory identified by a page structure instead of a virtual address. Those pages may or may not be highmem pages, and when they're highmem pages, they may or may not be virtually mapped. When they're not mapped then there is no L1 cache to worry about. But even in that case the L2 cache must be processed since unmapped highmem pages can still be L2 cached. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2009-03-13 02:52:09 +00:00
extern void *kmap_high_get(struct page *page);
ARM: 6639/1: allow highmem on SMP platforms without h/w TLB ops broadcast In commit e616c591405c168f6dc3dfd1221e105adfe49b8d, highmem support was deactivated for SMP platforms without hardware TLB ops broadcast because usage of kmap_high_get() requires that IRQs be disabled when kmap_lock is locked which is incompatible with the IPI mechanism used by the software TLB ops broadcast invoked through flush_all_zero_pkmaps(). The reason for kmap_high_get() is to ensure that the currently kmap'd page usage count does not decrease to zero while we're using its existing virtual mapping in an atomic context. With a VIVT cache this is essential to do due to cache coherency issues, but with a VIPT cache this is only an optimization so not to pay the price of establishing a second mapping if an existing one can be used. However, on VIPT platforms without hardware TLB maintenance we can give up on that optimization in order to be able to use highmem. From ARMv7 onwards the TLB ops are broadcasted in hardware, so let's disable ARCH_NEEDS_KMAP_HIGH_GET only when CONFIG_SMP and CONFIG_CPU_TLB_V6 are defined. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org> Tested-by: Saeed Bishara <saeed.bishara@gmail.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2011-01-25 20:35:38 +00:00
#else
static inline void *kmap_high_get(struct page *page)
{
return NULL;
}
#endif
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-15 20:44:55 +00:00
ARM: 6007/1: fix highmem with VIPT cache and DMA The VIVT cache of a highmem page is always flushed before the page is unmapped. This cache flush is explicit through flush_cache_kmaps() in flush_all_zero_pkmaps(), or through __cpuc_flush_dcache_area() in kunmap_atomic(). There is also an implicit flush of those highmem pages that were part of a process that just terminated making those pages free as the whole VIVT cache has to be flushed on every task switch. Hence unmapped highmem pages need no cache maintenance in that case. However unmapped pages may still be cached with a VIPT cache because the cache is tagged with physical addresses. There is no need for a whole cache flush during task switching for that reason, and despite the explicit cache flushes in flush_all_zero_pkmaps() and kunmap_atomic(), some highmem pages that were mapped in user space end up still cached even when they become unmapped. So, we do have to perform cache maintenance on those unmapped highmem pages in the context of DMA when using a VIPT cache. Unfortunately, it is not possible to perform that cache maintenance using physical addresses as all the L1 cache maintenance coprocessor functions accept virtual addresses only. Therefore we have no choice but to set up a temporary virtual mapping for that purpose. And of course the explicit cache flushing when unmapping a highmem page on a system with a VIPT cache now can go, which should increase performance. While at it, because the code in __flush_dcache_page() has to be modified anyway, let's also make sure the mapped highmem pages are pinned with kmap_high_get() for the duration of the cache maintenance operation. Because kunmap() does unmap highmem pages lazily, it was reported by Gary King <GKing@nvidia.com> that those pages ended up being unmapped during cache maintenance on SMP causing segmentation faults. Signed-off-by: Nicolas Pitre <nico@marvell.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-03-29 20:46:02 +00:00
/*
* The following functions are already defined by <linux/highmem.h>
* when CONFIG_HIGHMEM is not set.
*/
#ifdef CONFIG_HIGHMEM
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-15 20:44:55 +00:00
extern void *kmap(struct page *page);
extern void kunmap(struct page *page);
mm: stack based kmap_atomic() Keep the current interface but ignore the KM_type and use a stack based approach. The advantage is that we get rid of crappy code like: #define __KM_PTE \ (in_nmi() ? KM_NMI_PTE : \ in_irq() ? KM_IRQ_PTE : \ KM_PTE0) and in general can stop worrying about what context we're in and what kmap slots might be appropriate for that. The downside is that FRV kmap_atomic() gets more expensive. For now we use a CPP trick suggested by Andrew: #define kmap_atomic(page, args...) __kmap_atomic(page) to avoid having to touch all kmap_atomic() users in a single patch. [ not compiled on: - mn10300: the arch doesn't actually build with highmem to begin with ] [akpm@linux-foundation.org: coding-style fixes] [akpm@linux-foundation.org: fix up drivers/gpu/drm/i915/intel_overlay.c] Acked-by: Rik van Riel <riel@redhat.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Chris Metcalf <cmetcalf@tilera.com> Cc: David Howells <dhowells@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Ralf Baechle <ralf@linux-mips.org> Cc: David Miller <davem@davemloft.net> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Dave Airlie <airlied@linux.ie> Cc: Li Zefan <lizf@cn.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2010-10-26 21:21:51 +00:00
extern void *__kmap_atomic(struct page *page);
extern void __kunmap_atomic(void *kvaddr);
extern void *kmap_atomic_pfn(unsigned long pfn);
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-15 20:44:55 +00:00
extern struct page *kmap_atomic_to_page(const void *ptr);
ARM: 6007/1: fix highmem with VIPT cache and DMA The VIVT cache of a highmem page is always flushed before the page is unmapped. This cache flush is explicit through flush_cache_kmaps() in flush_all_zero_pkmaps(), or through __cpuc_flush_dcache_area() in kunmap_atomic(). There is also an implicit flush of those highmem pages that were part of a process that just terminated making those pages free as the whole VIVT cache has to be flushed on every task switch. Hence unmapped highmem pages need no cache maintenance in that case. However unmapped pages may still be cached with a VIPT cache because the cache is tagged with physical addresses. There is no need for a whole cache flush during task switching for that reason, and despite the explicit cache flushes in flush_all_zero_pkmaps() and kunmap_atomic(), some highmem pages that were mapped in user space end up still cached even when they become unmapped. So, we do have to perform cache maintenance on those unmapped highmem pages in the context of DMA when using a VIPT cache. Unfortunately, it is not possible to perform that cache maintenance using physical addresses as all the L1 cache maintenance coprocessor functions accept virtual addresses only. Therefore we have no choice but to set up a temporary virtual mapping for that purpose. And of course the explicit cache flushing when unmapping a highmem page on a system with a VIPT cache now can go, which should increase performance. While at it, because the code in __flush_dcache_page() has to be modified anyway, let's also make sure the mapped highmem pages are pinned with kmap_high_get() for the duration of the cache maintenance operation. Because kunmap() does unmap highmem pages lazily, it was reported by Gary King <GKing@nvidia.com> that those pages ended up being unmapped during cache maintenance on SMP causing segmentation faults. Signed-off-by: Nicolas Pitre <nico@marvell.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-03-29 20:46:02 +00:00
#endif
[ARM] kmap support The kmap virtual area borrows a 2MB range at the top of the 16MB area below PAGE_OFFSET currently reserved for kernel modules and/or the XIP kernel. This 2MB corresponds to the range covered by 2 consecutive second-level page tables, or a single pmd entry as seen by the Linux page table abstraction. Because XIP kernels are unlikely to be seen on systems needing highmem support, there shouldn't be any shortage of VM space for modules (14 MB for modules is still way more than twice the typical usage). Because the virtual mapping of highmem pages can go away at any moment after kunmap() is called on them, we need to bypass the delayed cache flushing provided by flush_dcache_page() in that case. The atomic kmap versions are based on fixmaps, and __cpuc_flush_dcache_page() is used directly in that case. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-15 20:44:55 +00:00
#endif
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