arm64: Avoid cache flushing in flush_dcache_page()
commit b5b6c9e9149d8a7c3f1d7b9d0c046c6184e1dd17 upstream.
The flush_dcache_page() function is called when the kernel modified a
page cache page. Since the D-cache on AArch64 does not have aliases
this function can simply mark the page as dirty for later flushing via
set_pte_at()/__sync_icache_dcache() if the page is executable (to ensure
the I-D cache coherency).
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Will Deacon <will.deacon@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 1e616427f20943c9966296dfff9e7a2b825846aa)
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index 88611c3..b9cd7a4 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -94,28 +94,14 @@
}
/*
- * Ensure cache coherency between kernel mapping and userspace mapping of this
- * page.
+ * This function is called when a page has been modified by the kernel. Mark
+ * it as dirty for later flushing when mapped in user space (if executable,
+ * see __sync_icache_dcache).
*/
void flush_dcache_page(struct page *page)
{
- struct address_space *mapping;
-
- /*
- * The zero page is never written to, so never has any dirty cache
- * lines, and therefore never needs to be flushed.
- */
- if (page == ZERO_PAGE(0))
- return;
-
- mapping = page_mapping(page);
- if (mapping && mapping_mapped(mapping)) {
- __flush_dcache_page(page);
- __flush_icache_all();
- set_bit(PG_dcache_clean, &page->flags);
- } else {
+ if (test_bit(PG_dcache_clean, &page->flags))
clear_bit(PG_dcache_clean, &page->flags);
- }
}
EXPORT_SYMBOL(flush_dcache_page);