Re: [Linaro-mm-sig] [PATCH v3] staging: android: ion: Zero CMA allocated memory

[Laura Abbott]

On 01/26/2018 06:04 PM, Chen Feng wrote:



On 2018/1/27 1:48, Liam Mark wrote:

Since commit 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
the CMA API is now used directly and therefore the allocated memory is no
longer automatically zeroed.

Explicitly zero CMA allocated memory to ensure that no data is exposed to
userspace.

Fixes: 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
Signed-off-by: Liam Mark 
---
Changes in v2:
   - Clean up the commit message.
   - Add 'Fixes:'

Changes in v3:
  - Add support for highmem pages

  drivers/staging/android/ion/ion_cma_heap.c | 17 +
  1 file changed, 17 insertions(+)

diff --git a/drivers/staging/android/ion/ion_cma_heap.c 
b/drivers/staging/android/ion/ion_cma_heap.c
index 86196ffd2faf..fa3e4b7e0c9f 100644
--- a/drivers/staging/android/ion/ion_cma_heap.c
+++ b/drivers/staging/android/ion/ion_cma_heap.c
@@ -21,6 +21,7 @@
  #include 
  #include 
  #include 
+#include 
  
  #include "ion.h"
  
@@ -51,6 +52,22 @@ static int ion_cma_allocate(struct ion_heap *heap, struct ion_buffer *buffer,

if (!pages)
return -ENOMEM;
  
+	if (PageHighMem(pages)) {

+   unsigned long nr_clear_pages = nr_pages;
+   struct page *page = pages;
+
+   while (nr_clear_pages > 0) {
+   void *vaddr = kmap_atomic(page);
+
+   memset(vaddr, 0, PAGE_SIZE);
+   kunmap_atomic(vaddr);


Here. This way may cause performance latency at mapping-memset-umap page one 
bye one.

Take a look at ion_heap_pages_zero.

Not very critical, arm64 always have linear mapping.



This is under a PageHighMem check so arm64 isn't affected. It's also
the same algorithm arm32 dma-mapping.c uses so I'd like to see some
data about the performance improvement before we go changing things
too much.

Thanks,
Laura




+   page++;
+   nr_clear_pages--;
+   }
+   } else {
+   memset(page_address(pages), 0, size);
+   }
+
table = kmalloc(sizeof(*table), GFP_KERNEL);
if (!table)
goto err;





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Re: [Linaro-mm-sig] [PATCH v3] staging: android: ion: Zero CMA allocated memory

[Chen Feng]

On 2018/1/27 1:48, Liam Mark wrote:
> Since commit 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
> the CMA API is now used directly and therefore the allocated memory is no
> longer automatically zeroed.
> 
> Explicitly zero CMA allocated memory to ensure that no data is exposed to
> userspace.
> 
> Fixes: 204f672255c2 ("staging: android: ion: Use CMA APIs directly")
> Signed-off-by: Liam Mark 
> ---
> Changes in v2:
>   - Clean up the commit message.
>   - Add 'Fixes:'
> 
> Changes in v3:
>  - Add support for highmem pages
> 
>  drivers/staging/android/ion/ion_cma_heap.c | 17 +
>  1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/staging/android/ion/ion_cma_heap.c 
> b/drivers/staging/android/ion/ion_cma_heap.c
> index 86196ffd2faf..fa3e4b7e0c9f 100644
> --- a/drivers/staging/android/ion/ion_cma_heap.c
> +++ b/drivers/staging/android/ion/ion_cma_heap.c
> @@ -21,6 +21,7 @@
>  #include 
>  #include 
>  #include 
> +#include 
>  
>  #include "ion.h"
>  
> @@ -51,6 +52,22 @@ static int ion_cma_allocate(struct ion_heap *heap, struct 
> ion_buffer *buffer,
>   if (!pages)
>   return -ENOMEM;
>  
> + if (PageHighMem(pages)) {
> + unsigned long nr_clear_pages = nr_pages;
> + struct page *page = pages;
> +
> + while (nr_clear_pages > 0) {
> + void *vaddr = kmap_atomic(page);
> +
> + memset(vaddr, 0, PAGE_SIZE);
> + kunmap_atomic(vaddr);

Here. This way may cause performance latency at mapping-memset-umap page one 
bye one.

Take a look at ion_heap_pages_zero.

Not very critical, arm64 always have linear mapping.


> + page++;
> + nr_clear_pages--;
> + }
> + } else {
> + memset(page_address(pages), 0, size);
> + }
> +
>   table = kmalloc(sizeof(*table), GFP_KERNEL);
>   if (!table)
>   goto err;
> 

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