From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Thu, 17 Jul 2014 18:15:50 +0100 Subject: [PATCH] ARM: DMA: ensure that old section mappings are flushed from the TLB In-Reply-To: References: Message-ID: <20140717171550.GA4844@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jul 17, 2014 at 04:38:17PM +0100, Russell King wrote: > When setting up the CMA region, we must ensure that the old section > mappings are flushed from the TLB before replacing them with page > tables, otherwise we can suffer from mismatched aliases if the CPU > speculatively prefetches from these mappings at an inopportune time. > > A mismatched alias can occur when the TLB contains a section mapping, > but a subsequent prefetch causes it to load a page table mapping, > resulting in the possibility of the TLB containing two matching > mappings for the same virtual address region. > > Signed-off-by: Russell King Acked-by: Will Deacon Will > --- > arch/arm/mm/dma-mapping.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index 4c88935654ca..1f88db06b133 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -461,12 +461,21 @@ void __init dma_contiguous_remap(void) > map.type = MT_MEMORY_DMA_READY; > > /* > - * Clear previous low-memory mapping > + * Clear previous low-memory mapping to ensure that the > + * TLB does not see any conflicting entries, then flush > + * the TLB of the old entries before creating new mappings. > + * > + * This ensures that any speculatively loaded TLB entries > + * (even though they may be rare) can not cause any problems, > + * and ensures that this code is architecturally compliant. > */ > for (addr = __phys_to_virt(start); addr < __phys_to_virt(end); > addr += PMD_SIZE) > pmd_clear(pmd_off_k(addr)); > > + flush_tlb_kernel_range(__phys_to_virt(start), > + __phys_to_virt(end)); > + > iotable_init(&map, 1); > } > } > -- > 1.8.3.1 > >