arm64: Do not flush the D-cache for anonymous pages

The D-cache on AArch64 is VIPT non-aliasing, so there is no need to
flush it for anonymous pages.

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>

2 files changed, 3 insertions, 6 deletions

diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index b9cd7a4deeca..7c716634a671 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -77,14 +77,12 @@ void __flush_dcache_page(struct page *page)
 
 void __sync_icache_dcache(pte_t pte, unsigned long addr)
 {
-        unsigned long pfn;
-        struct page *page;
+        struct page *page = pte_page(pte);
 
-        pfn = pte_pfn(pte);
-        if (!pfn_valid(pfn))
+        /* no flushing needed for anonymous pages */
+        if (!page_mapping(page))
                 return;
 
-        page = pfn_to_page(pfn);
         if (!test_and_set_bit(PG_dcache_clean, &page->flags)) {
                 __flush_dcache_page(page);
                 __flush_icache_all();
diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index eeecc9c8ed68..80a369eab637 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -339,7 +339,6 @@ void __init paging_init(void)
         bootmem_init();
 
         empty_zero_page = virt_to_page(zero_page);
-        __flush_dcache_page(empty_zero_page);
 
         /*
          * TTBR0 is only used for the identity mapping at this stage. Make it