ARC: [mm] Aliasing VIPT dcache support 2/4
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>
diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c
index 5810c7a..066145b 100644
--- a/arch/arc/mm/tlb.c
+++ b/arch/arc/mm/tlb.c
@@ -421,25 +421,40 @@
/*
* 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);
}
}
}