Re: [PATCH v3 0/9] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths

[Mostafa Saleh]

On Fri, May 08, 2026 at 06:28:11PM +0100, Catalin Marinas wrote:
> On Mon, Apr 27, 2026 at 11:25:00AM +0530, Aneesh Kumar K.V (Arm) wrote:
> > This series propagates DMA_ATTR_CC_SHARED through the dma-direct,
> > dma-pool, and swiotlb paths so that encrypted and decrypted DMA buffers
> > are handled consistently.
> 
> I think this series makes sense, using DMA_ATTR_CC_SHARED throughout the
> DMA API, either for alloc or for streaming to decide/check what bouncing
> does. Sashiko has a few interesting reports, it probably breaks s390 as
> well (it might be similar to the pKVM case).

I have this series on my review list, I believe there is an overlap with
my series, I can rebase mine on top of this if that makes sense, I will
probably wait for a new version to address the current comments and
Sashiko notes.

Thanks,
Mostafa

> 
> I don't think it addresses earlier Mostafa's issues with pKVM, although
> I'd rather base additional pKVM related fixes on top of this series.
> With pKVM, cc_platform_has(CC_ATTR_MEM_ENCRYPT) returns false, as does
> force_dma_unencrypted(). I think we should update protected guests to
> return true for these if they need shared buffers (the whole
> decrypted/shared terminology is messy but in most places it just means
> buffer not private to the protected guest, whether encryption is
> available or not).
> 
> That said, does CC_ATTR_GUEST_MEM_ENCRYPT actually make more sense than
> CC_ATTR_MEM_ENCRYPT throughout this series? We'd need to change arm64
> realms as well to use this one.
> 
> -- 
> Catalin