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parisc: fixes and cleanups in page cache flushing (4/4)

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CONFIG_PARISC_TMPALIAS enables clear_user_highpage and copy_user_highpage.
These are essentially alternative implementations of clear_user_page and
copy_user_page.  They don't have anything to do with x86 high pages, but they
build on the infrastructure to save a few instructions.  Read the comment in
clear_user_highpage as it is very important to the implementation.  For this
reason, there isn't any gain in using the TMPALIAS/highpage approach.

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
John David Anglin 2013-02-03 23:02:49 +00:00 committed by Helge Deller
parent 6d2439d955
commit cca8e90260
1 changed files with 64 additions and 0 deletions
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64
arch/parisc/kernel/cache.c
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@ -596,3 +596,67 @@ flush_cache_page(struct vm_area_struct *vma, unsigned long vmaddr, unsigned long
__flush_cache_page(vma, vmaddr, page_to_phys(pfn_to_page(pfn)));
}
#ifdef CONFIG_PARISC_TMPALIAS
void clear_user_highpage(struct page *page, unsigned long vaddr)
{
void *vto;
unsigned long flags;
/* Clear using TMPALIAS region. The page doesn't need to
be flushed but the kernel mapping needs to be purged. */
vto = kmap_atomic(page, KM_USER0);
/* The PA-RISC 2.0 Architecture book states on page F-6:
"Before a write-capable translation is enabled, *all*
non-equivalently-aliased translations must be removed
from the page table and purged from the TLB. (Note
that the caches are not required to be flushed at this
time.) Before any non-equivalent aliased translation
is re-enabled, the virtual address range for the writeable
page (the entire page) must be flushed from the cache,
and the write-capable translation removed from the page
table and purged from the TLB." */
purge_kernel_dcache_page_asm((unsigned long)vto);
purge_tlb_start(flags);
pdtlb_kernel(vto);
purge_tlb_end(flags);
preempt_disable();
clear_user_page_asm(vto, vaddr);
preempt_enable();
pagefault_enable(); /* kunmap_atomic(addr, KM_USER0); */
}
void copy_user_highpage(struct page *to, struct page *from,
unsigned long vaddr, struct vm_area_struct *vma)
{
void *vfrom, *vto;
unsigned long flags;
/* Copy using TMPALIAS region. This has the advantage
that the `from' page doesn't need to be flushed. However,
the `to' page must be flushed in copy_user_page_asm since
it can be used to bring in executable code. */
vfrom = kmap_atomic(from, KM_USER0);
vto = kmap_atomic(to, KM_USER1);
purge_kernel_dcache_page_asm((unsigned long)vto);
purge_tlb_start(flags);
pdtlb_kernel(vto);
pdtlb_kernel(vfrom);
purge_tlb_end(flags);
preempt_disable();
copy_user_page_asm(vto, vfrom, vaddr);
flush_dcache_page_asm(__pa(vto), vaddr);
preempt_enable();
pagefault_enable(); /* kunmap_atomic(addr, KM_USER1); */
pagefault_enable(); /* kunmap_atomic(addr, KM_USER0); */
}
#endif /* CONFIG_PARISC_TMPALIAS */