Hi All,
On 2018-11-30 20:05, Robin Murphy wrote:
> On 05/11/2018 12:19, Christoph Hellwig wrote:
>> By using __dma_direct_alloc_pages we can deal entirely with struct page
>> instead of having to derive a kernel virtual address.
>
> Simple enough :)
>
> Reviewed-by: Robin Murphy <robin.mur...@arm.com>
This patch has landed linux-next yesterday and I've noticed that it
breaks operation of many drivers. The change looked simple, but a stupid
bug managed to slip into the code. After a short investigation I've
noticed that __dma_direct_alloc_pages() doesn't set dma_handle and zero
allocated memory, while dma_direct_alloc_pages() did. The other
difference is the lack of set_memory_decrypted() handling.
Following patch fixes the issue, but maybe it would be better to fix it
in kernel/dma/direct.c:
diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
index dcc82dd668f8..7765ddc56e4e 100644
--- a/kernel/dma/remap.c
+++ b/kernel/dma/remap.c
@@ -219,8 +219,14 @@ void *arch_dma_alloc(struct device *dev, size_t
size, dma_addr_t *dma_handle,
ret = dma_common_contiguous_remap(page, size, VM_USERMAP,
arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs),
__builtin_return_address(0));
- if (!ret)
+ if (!ret) {
__dma_direct_free_pages(dev, size, page);
+ return ret;
+ }
+
+ *dma_handle = phys_to_dma(dev, page_to_phys(page));
+ memset(ret, 0, size);
+
return ret;
}
>
>> Signed-off-by: Christoph Hellwig <h...@lst.de>
>> ---
>> kernel/dma/remap.c | 14 +++++++-------
>> 1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/kernel/dma/remap.c b/kernel/dma/remap.c
>> index bc42766f52df..8f1fca34b894 100644
>> --- a/kernel/dma/remap.c
>> +++ b/kernel/dma/remap.c
>> @@ -196,7 +196,7 @@ void *arch_dma_alloc(struct device *dev, size_t
>> size, dma_addr_t *dma_handle,
>> gfp_t flags, unsigned long attrs)
>> {
>> struct page *page = NULL;
>> - void *ret, *kaddr;
>> + void *ret;
>> size = PAGE_ALIGN(size);
>> @@ -208,10 +208,9 @@ void *arch_dma_alloc(struct device *dev,
>> size_t size, dma_addr_t *dma_handle,
>> return ret;
>> }
>> - kaddr = dma_direct_alloc_pages(dev, size, dma_handle, flags,
>> attrs);
>> - if (!kaddr)
>> + page = __dma_direct_alloc_pages(dev, size, dma_handle, flags,
>> attrs);
>> + if (!page)
>> return NULL;
>> - page = virt_to_page(kaddr);
>> /* remove any dirty cache lines on the kernel alias */
>> arch_dma_prep_coherent(page, size);
>> @@ -221,7 +220,7 @@ void *arch_dma_alloc(struct device *dev, size_t
>> size, dma_addr_t *dma_handle,
>> arch_dma_mmap_pgprot(dev, PAGE_KERNEL, attrs),
>> __builtin_return_address(0));
>> if (!ret)
>> - dma_direct_free_pages(dev, size, kaddr, *dma_handle, attrs);
>> + __dma_direct_free_pages(dev, size, page);
>> return ret;
>> }
>> @@ -229,10 +228,11 @@ void arch_dma_free(struct device *dev, size_t
>> size, void *vaddr,
>> dma_addr_t dma_handle, unsigned long attrs)
>> {
>> if (!dma_free_from_pool(vaddr, PAGE_ALIGN(size))) {
>> - void *kaddr = phys_to_virt(dma_to_phys(dev, dma_handle));
>> + phys_addr_t phys = dma_to_phys(dev, dma_handle);
>> + struct page *page = pfn_to_page(__phys_to_pfn(phys));
>> vunmap(vaddr);
>> - dma_direct_free_pages(dev, size, kaddr, dma_handle, attrs);
>> + __dma_direct_free_pages(dev, size, page);
>> }
>> }
>>
>
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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