sh: Improve performance of SH4 versions of copy/clear_user_highpage
The previous implementation of clear_user_highpage and copy_user_highpage checked to see if there was a D-cache aliasing issue between the user and kernel mappings of a page, but if there was they always did a flush with writeback on the dirtied kernel alias. However as we now have the ability to map a page into kernel space with the same cache colour as the user mapping, there is no need to write back this data. Currently we also invalidate the kernel alias as a precaution, however I'm not sure if this is actually required. Also correct the definition of FIX_CMAP_END so that the mappings created by kmap_coherent() are actually at the correct colour. Signed-off-by: Stuart Menefy <stuart.menefy@st.com> Signed-off-by: Paul Mundt <lethal@linux-sh.org>
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@ -46,9 +46,15 @@
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* fix-mapped?
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*/
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enum fixed_addresses {
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/*
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* The FIX_CMAP entries are used by kmap_coherent() to get virtual
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* addresses which are of a known color, and so their values are
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* important. __fix_to_virt(FIX_CMAP_END - n) must give an address
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* which is the same color as a page (n<<PAGE_SHIFT).
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*/
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#define FIX_N_COLOURS 8
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FIX_CMAP_BEGIN,
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FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS),
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FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS) - 1,
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FIX_UNCACHED,
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#ifdef CONFIG_HIGHMEM
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FIX_KMAP_BEGIN, /* reserved pte's for temporary kernel mappings */
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@ -46,6 +46,18 @@ static inline void cacheop_on_each_cpu(void (*func) (void *info), void *info,
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preempt_enable();
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}
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/*
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* copy_to_user_page
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* @vma: vm_area_struct holding the pages
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* @page: struct page
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* @vaddr: user space address
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* @dst: address of page in kernel space (possibly from kmap)
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* @src: source address in kernel logical memory
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* @len: length of data in bytes (may be less than PAGE_SIZE)
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*
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* Copy data into the address space of a process other than the current
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* process (eg for ptrace).
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*/
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void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
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unsigned long vaddr, void *dst, const void *src,
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unsigned long len)
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@ -81,28 +93,49 @@ void copy_from_user_page(struct vm_area_struct *vma, struct page *page,
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}
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}
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/*
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* copy_user_highpage
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* @to: destination page
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* @from: source page
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* @vaddr: address of pages in user address space
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* @vma: vm_area_struct holding the pages
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*
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* This is used in COW implementation to copy data from page @from to
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* page @to. @from was previousl mapped at @vaddr, and @to will be.
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* As this is used only in the COW implementation, this means that the
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* source is unmodified, and so we don't have to worry about cache
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* aliasing on that side.
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*/
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#ifdef CONFIG_HIGHMEM
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/*
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* If we ever have a real highmem system, this code will need fixing
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* (as will clear_user/clear_user_highmem), because the kmap potentitally
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* creates another alias risk.
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*/
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#error This code is broken with real HIGHMEM
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#endif
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void copy_user_highpage(struct page *to, struct page *from,
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unsigned long vaddr, struct vm_area_struct *vma)
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{
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void *vfrom, *vto;
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vto = kmap_atomic(to, KM_USER1);
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vfrom = kmap_atomic(from, KM_USER0);
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if (pages_do_alias((unsigned long)vto, vaddr & PAGE_MASK))
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__flush_invalidate_region(vto, PAGE_SIZE);
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if (boot_cpu_data.dcache.n_aliases && page_mapped(from) &&
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!test_bit(PG_dcache_dirty, &from->flags)) {
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vfrom = kmap_coherent(from, vaddr);
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void *vto_coloured = kmap_coherent(to, vaddr);
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copy_page(vto_coloured, vfrom);
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kunmap_coherent(vto_coloured);
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} else
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copy_page(vto, vfrom);
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kunmap_coherent(vfrom);
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} else {
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vfrom = kmap_atomic(from, KM_USER0);
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copy_page(vto, vfrom);
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kunmap_atomic(vfrom, KM_USER0);
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}
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if (pages_do_alias((unsigned long)vto, vaddr & PAGE_MASK))
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__flush_purge_region(vto, PAGE_SIZE);
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kunmap_atomic(vfrom, KM_USER0);
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kunmap_atomic(vto, KM_USER1);
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/* Make sure this page is cleared on other CPU's too before using it */
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smp_wmb();
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}
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@ -112,10 +145,17 @@ void clear_user_highpage(struct page *page, unsigned long vaddr)
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{
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void *kaddr = kmap_atomic(page, KM_USER0);
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clear_page(kaddr);
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if (pages_do_alias((unsigned long)kaddr, vaddr & PAGE_MASK)) {
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void *vto;
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if (pages_do_alias((unsigned long)kaddr, vaddr & PAGE_MASK))
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__flush_purge_region(kaddr, PAGE_SIZE);
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/* Kernel alias may have modified data in the cache. */
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__flush_invalidate_region(kaddr, PAGE_SIZE);
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vto = kmap_coherent(page, vaddr);
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clear_page(vto);
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kunmap_coherent(vto);
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} else
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clear_page(kaddr);
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kunmap_atomic(kaddr, KM_USER0);
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}
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