Commit 39ac11c1 authored by Stuart Menefy's avatar Stuart Menefy Committed by Paul Mundt
Browse files

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: default avatarStuart Menefy <stuart.menefy@st.com>
Signed-off-by: default avatarPaul Mundt <lethal@linux-sh.org>
parent 49fb2cd2

arch/sh/include/asm/fixmap.h

+7 −1
Original line number Diff line number Diff line
@@ -46,9 +46,15 @@ 
 * fix-mapped?

 */

enum fixed_addresses {

	/*

	 * The FIX_CMAP entries are used by kmap_coherent() to get virtual

	 * addresses which are of a known color, and so their values are

	 * important. __fix_to_virt(FIX_CMAP_END - n) must give an address

	 * which is the same color as a page (n<<PAGE_SHIFT).

	 */

#define FIX_N_COLOURS 8

	FIX_CMAP_BEGIN,

	FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS),

	FIX_CMAP_END = FIX_CMAP_BEGIN + (FIX_N_COLOURS * NR_CPUS) - 1,

	FIX_UNCACHED,

#ifdef CONFIG_HIGHMEM

	FIX_KMAP_BEGIN,	/* reserved pte's for temporary kernel mappings */

arch/sh/mm/cache.c

+53 −13
Original line number Diff line number Diff line
@@ -46,6 +46,18 @@ static inline void cacheop_on_each_cpu(void (*func) (void *info), void *info, 
	preempt_enable();

}



/*

 * copy_to_user_page

 * @vma: vm_area_struct holding the pages

 * @page: struct page

 * @vaddr: user space address

 * @dst: address of page in kernel space (possibly from kmap)

 * @src: source address in kernel logical memory

 * @len: length of data in bytes (may be less than PAGE_SIZE)

 *

 * Copy data into the address space of a process other than the current

 * process (eg for ptrace).

 */

void copy_to_user_page(struct vm_area_struct *vma, struct page *page,

		       unsigned long vaddr, void *dst, const void *src,

		       unsigned long len)
@@ -81,28 +93,49 @@ void copy_from_user_page(struct vm_area_struct *vma, struct page *page, 
	}

}



/*

 * copy_user_highpage

 * @to: destination page

 * @from: source page

 * @vaddr: address of pages in user address space

 * @vma: vm_area_struct holding the pages

 *

 * This is used in COW implementation to copy data from page @from to

 * page @to. @from was previousl mapped at @vaddr, and @to will be.

 * As this is used only in the COW implementation, this means that the

 * source is unmodified, and so we don't have to worry about cache

 * aliasing on that side.

 */

#ifdef CONFIG_HIGHMEM

/*

 * If we ever have a real highmem system, this code will need fixing

 * (as will clear_user/clear_user_highmem), because the kmap potentitally

 * creates another alias risk.

 */

#error This code is broken with real HIGHMEM

#endif

void copy_user_highpage(struct page *to, struct page *from,

			unsigned long vaddr, struct vm_area_struct *vma)

{

	void *vfrom, *vto;



	vto = kmap_atomic(to, KM_USER1);

	vfrom = kmap_atomic(from, KM_USER0);



	if (pages_do_alias((unsigned long)vto, vaddr & PAGE_MASK))

		__flush_invalidate_region(vto, PAGE_SIZE);



	if (boot_cpu_data.dcache.n_aliases && page_mapped(from) &&

	    !test_bit(PG_dcache_dirty, &from->flags)) {

		vfrom = kmap_coherent(from, vaddr);

		copy_page(vto, vfrom);

		kunmap_coherent(vfrom);

	} else {

		vfrom = kmap_atomic(from, KM_USER0);

		void *vto_coloured = kmap_coherent(to, vaddr);

		copy_page(vto_coloured, vfrom);

		kunmap_coherent(vto_coloured);

	} else

		copy_page(vto, vfrom);

		kunmap_atomic(vfrom, KM_USER0);

	}



	if (pages_do_alias((unsigned long)vto, vaddr & PAGE_MASK))

		__flush_purge_region(vto, PAGE_SIZE);



	kunmap_atomic(vfrom, KM_USER0);

	kunmap_atomic(vto, KM_USER1);



	/* Make sure this page is cleared on other CPU's too before using it */

	smp_wmb();

}
@@ -112,10 +145,17 @@ void clear_user_highpage(struct page *page, unsigned long vaddr) 
{

	void *kaddr = kmap_atomic(page, KM_USER0);



	clear_page(kaddr);

	if (pages_do_alias((unsigned long)kaddr, vaddr & PAGE_MASK)) {

		void *vto;



		/* Kernel alias may have modified data in the cache. */

		__flush_invalidate_region(kaddr, PAGE_SIZE);



	if (pages_do_alias((unsigned long)kaddr, vaddr & PAGE_MASK))

		__flush_purge_region(kaddr, PAGE_SIZE);

		vto = kmap_coherent(page, vaddr);

		clear_page(vto);

		kunmap_coherent(vto);

	} else

		clear_page(kaddr);



	kunmap_atomic(kaddr, KM_USER0);

}