Re: [PATCH 10/10] arm64: use the generic swiotlb_dma_ops

Christoph Hellwig
2018-10-12T14:40:54Z

On Fri, Oct 12, 2018 at 02:01:00PM +0100, Robin Murphy wrote:
> On 08/10/18 09:02, Christoph Hellwig wrote:
>> Now that the generic swiotlb code supports non-coherent DMA we can switch
>> to it for arm64. For that we need to refactor the existing
>> alloc/free/mmap/pgprot helpers to be used as the architecture hooks,
>> and implement the standard arch_sync_dma_for_{device,cpu} hooks for
>> cache maintaincance in the streaming dma hooks, which also implies
>> using the generic dma_coherent flag in struct device.
>>
>> Note that we need to keep the old is_device_dma_coherent function around
>> for now, so that the shared arm/arm64 Xen code keeps working.
>
> OK, so when I said last night that it boot-tested OK, that much was true,
> but then I shut the board down as I left and got a megasplosion of bad page
> state BUGs, e.g.:

I think this is because I am passing the wrong address to
dma_direct_free_pages. Please try this patch on top:

diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
index 3c75d69b54e7..4f0f92856c4c 100644
--- a/arch/arm64/mm/dma-mapping.c
+++ b/arch/arm64/mm/dma-mapping.c
@@ -126,10 +126,12 @@ void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
void arch_dma_free(struct device *dev, size_t size, void *vaddr,
dma_addr_t dma_handle, unsigned long attrs)
{
- if (__free_from_pool(vaddr, PAGE_ALIGN(size)))
- return;
- vunmap(vaddr);
- dma_direct_free_pages(dev, size, vaddr, dma_handle, attrs);
+ if (!__free_from_pool(vaddr, PAGE_ALIGN(size)))
+ void *kaddr = phys_to_virt(dma_to_phys(dev, dma_handle));
+
+ vunmap(vaddr);
+ dma_direct_free_pages(dev, size, kaddr, dma_handle, attrs);
+ }
}

long arch_dma_coherent_to_pfn(struct device *dev, void *cpu_addr,