From: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
To: Jason Gunthorpe <jgg@ziepe.ca>,
Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
robin.murphy@arm.com, m.szyprowski@samsung.com, will@kernel.org,
maz@kernel.org, catalin.marinas@arm.com, jiri@resnulli.us,
Mostafa Saleh <smostafa@google.com>
Subject: Re: [PATCH v2 7/8] dma-direct: set decrypted flag for remapped DMA allocations
Date: Wed, 22 Apr 2026 10:54:26 +0530 [thread overview]
Message-ID: <yq5atst3d0tx.fsf@kernel.org> (raw)
In-Reply-To: <20260421135311.GH3611611@ziepe.ca>
Jason Gunthorpe <jgg@ziepe.ca> writes:
> On Tue, Apr 21, 2026 at 01:54:52PM +0100, Suzuki K Poulose wrote:
>> On 21/04/2026 13:34, Jason Gunthorpe wrote:
>> > On Mon, Apr 20, 2026 at 11:44:14AM +0530, Aneesh Kumar K.V (Arm) wrote:
>> > > Devices that are DMA non-coherent and require a remap were skipping
>> > > dma_set_decrypted(), leaving DMA buffers encrypted even when the device
>> > > requires unencrypted access. Move the call after the if (remap) branch
>> > > so that both the direct and remapped allocation paths correctly mark the
>> > > allocation as decrypted (or fail cleanly) before use.
>> > >
>> > > Architectures such as arm64 cannot mark vmap addresses as decrypted, and
>> > > highmem pages necessarily require a vmap remap.
>> >
>> > I don't think I saw an aswer for this, why can't arm accept
>> > pgprot_decrypted() for vmap? It really should, I don't think we should
>> > have these minor pointless arch differences.
>> >
>> > Suzuki? You mentioned it, can you elaborate?
>>
>> We can accept pgprot_decrypted(), but this must be done carefully
>> as the backing pages must be first converted to "decrypted" in the
>> linear map (set_memory_decrypted()).
>
> Isn't that the case for any use of pgprot_decrypted? I think that is
> fine and followed by the dma api.
>
>> With that in place, it should be fine. It is,
>> set_memory_decrypted(vmalloc_address) is we don't support.
>
> That makes more sense. Nothing should do that, changing the state of
> memory that is mapped any place other than the linear map is not
> allowed. I understand this is the condition where Intel will machine
> check..
>
> So with that clarification at least the commit message should be
> revised in this patch to not mention vmap.
>
I will update the commit message to clarify this further.
-aneesh
next prev parent reply other threads:[~2026-04-22 5:24 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-20 6:14 [PATCH v2 0/8] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Aneesh Kumar K.V (Arm)
2026-04-20 6:14 ` [PATCH v2 1/8] dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages Aneesh Kumar K.V (Arm)
2026-04-20 6:14 ` [PATCH v2 2/8] dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths Aneesh Kumar K.V (Arm)
2026-04-20 6:14 ` [PATCH v2 3/8] dma-pool: track decrypted atomic pools and select them via attrs Aneesh Kumar K.V (Arm)
2026-04-20 6:14 ` [PATCH v2 4/8] dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-04-20 6:14 ` [PATCH v2 5/8] dma-mapping: make dma_pgprot() " Aneesh Kumar K.V (Arm)
2026-04-20 6:14 ` [PATCH v2 6/8] dma-direct: make dma_direct_map_phys() " Aneesh Kumar K.V (Arm)
2026-04-21 12:29 ` Jason Gunthorpe
2026-04-22 5:50 ` Aneesh Kumar K.V
2026-04-22 6:16 ` Aneesh Kumar K.V
2026-04-20 6:14 ` [PATCH v2 7/8] dma-direct: set decrypted flag for remapped DMA allocations Aneesh Kumar K.V (Arm)
2026-04-21 12:34 ` Jason Gunthorpe
2026-04-21 12:54 ` Suzuki K Poulose
2026-04-21 13:53 ` Jason Gunthorpe
2026-04-22 5:24 ` Aneesh Kumar K.V [this message]
2026-04-20 6:14 ` [PATCH v2 8/8] dma-direct: select DMA address encoding from DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-04-21 12:40 ` [PATCH v2 0/8] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Jason Gunthorpe
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