Re: [PATCH v2] crypto: ccp - Allocate TEE ring and cmd buffer using DMA APIs

[Rijo Thomas <Rijo-john.Thomas@amd.com>]

On 12/30/2022 1:54 PM, Herbert Xu wrote:
> On Fri, Dec 23, 2022 at 05:45:24PM +0530, Rijo Thomas wrote:
>>
>>> dma_alloc_coherent memory is just as contiguous as __get_free_pages, and
>>> calling dma_alloc_coherent from a guest does not guarantee that the memory is
>>> contiguous in host memory either. The memory would look contiguous from the
>>> device point of view thanks to the IOMMU though (in both cases). So this is not
>>> about being contiguous but other properties that you might rely on (dma mask
>>> most likely, or coherent if you're not running this on x86?).
>>>
>>> Can you confirm why this fixes things and update the comment to reflect that.
>>
>> I see what you are saying.
>>
>> We verified this in Xen Dom0 PV guest, where dma_alloc_coherent() returned a memory
>> that is contiguous in machine address space, and the machine address was returned
>> in the dma handle (buf->dma).
> 
> So is this even relevant to the mainstream kernel or is this patch
> only needed for Xen Dom0?
> 
> Thanks,

Herbert,

This patch is no longer relevant to the mainstream kernel.

Thanks,
Rijo