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ARC: [mm] Aliasing VIPT dcache support 2/4

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This is the meat of the series which prevents any dcache alias creation
by always keeping the U and K mapping of a page congruent.
If a mapping already exists, and other tries to access the page, prev
one is flushed to physical page (wback+inv)

Essentially flush_dcache_page()/copy_user_highpage() create K-mapping
of a page, but try to defer flushing, unless U-mapping exist.
When page is actually mapped to userspace, update_mmu_cache() flushes
the K-mapping (in certain cases this can be optimised out)

Additonally flush_cache_mm(), flush_cache_range(), flush_cache_page()
handle the puring of stale userspace mappings on exit/munmap...

flush_anon_page() handles the existing U-mapping for anon page before
kernel reads it via the GUP path.

Note that while not complete, this is enough to boot a simple
dynamically linked Busybox based rootfs

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
This commit is contained in:
Vineet Gupta
2013-05-09 21:54:51 +05:30
parent 6ec18a81b2
commit 4102b53392
6 changed files with 223 additions and 22 deletions
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27
arch/arc/mm/tlb.c
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@@ -421,25 +421,40 @@ void create_tlb(struct vm_area_struct *vma, unsigned long address, pte_t *ptep)
/*
* Called at the end of pagefault, for a userspace mapped page
* -pre-install the corresponding TLB entry into MMU
* -Finalize the delayed D-cache flush (wback+inv kernel mapping)
* -Finalize the delayed D-cache flush of kernel mapping of page due to
* flush_dcache_page(), copy_user_page()
*
* Note that flush (when done) involves both WBACK - so physical page is
* in sync as well as INV - so any non-congruent aliases don't remain
*/
void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddr_unaligned,
pte_t *ptep)
{
unsigned long vaddr = vaddr_unaligned & PAGE_MASK;
unsigned long paddr = pte_val(*ptep) & PAGE_MASK;
create_tlb(vma, vaddr, ptep);
/* icache doesn't snoop dcache, thus needs to be made coherent here */
if (vma->vm_flags & VM_EXEC) {
/*
* Exec page : Independent of aliasing/page-color considerations,
* since icache doesn't snoop dcache on ARC, any dirty
* K-mapping of a code page needs to be wback+inv so that
* icache fetch by userspace sees code correctly.
* !EXEC page: If K-mapping is NOT congruent to U-mapping, flush it
* so userspace sees the right data.
* (Avoids the flush for Non-exec + congruent mapping case)
*/
if (vma->vm_flags & VM_EXEC || addr_not_cache_congruent(paddr, vaddr)) {
struct page *page = pfn_to_page(pte_pfn(*ptep));
/* if page was dcache dirty, flush now */
int dirty = test_and_clear_bit(PG_arch_1, &page->flags);
if (dirty) {
unsigned long paddr = pte_val(*ptep) & PAGE_MASK;
/* wback + inv dcache lines */
__flush_dcache_page(paddr, paddr);
__inv_icache_page(paddr, vaddr);
/* invalidate any existing icache lines */
if (vma->vm_flags & VM_EXEC)
__inv_icache_page(paddr, vaddr);
}
}
}