From: Aneesh Kumar K.V <aneesh.kumar@kernel•org>
To: Jason Gunthorpe <jgg@ziepe•ca>, Mostafa Saleh <smostafa@google•com>
Cc: iommu@lists•linux.dev, linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, linux-coco@lists•linux.dev,
Robin Murphy <robin.murphy@arm•com>,
Marek Szyprowski <m.szyprowski@samsung•com>,
Will Deacon <will@kernel•org>, Marc Zyngier <maz@kernel•org>,
Steven Price <steven.price@arm•com>,
Suzuki K Poulose <Suzuki.Poulose@arm•com>,
Catalin Marinas <catalin.marinas@arm•com>,
Jiri Pirko <jiri@resnulli•us>, Petr Tesarik <ptesarik@suse•com>,
Alexey Kardashevskiy <aik@amd•com>,
Dan Williams <dan.j.williams@intel•com>,
Xu Yilun <yilun.xu@linux•intel.com>,
linuxppc-dev@lists•ozlabs.org, linux-s390@vger•kernel.org,
Madhavan Srinivasan <maddy@linux•ibm.com>,
Michael Ellerman <mpe@ellerman•id.au>,
Nicholas Piggin <npiggin@gmail•com>,
"Christophe Leroy (CS GROUP)" <chleroy@kernel•org>,
Alexander Gordeev <agordeev@linux•ibm.com>,
Gerald Schaefer <gerald.schaefer@linux•ibm.com>,
Heiko Carstens <hca@linux•ibm.com>,
Vasily Gorbik <gor@linux•ibm.com>,
Christian Borntraeger <borntraeger@linux•ibm.com>,
Sven Schnelle <svens@linux•ibm.com>,
x86@kernel•org
Subject: Re: [PATCH v4 04/13] dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_SHARED
Date: Thu, 14 May 2026 11:54:30 +0530 [thread overview]
Message-ID: <yq5aecjea4pt.fsf@kernel.org> (raw)
In-Reply-To: <20260513172450.GR7702@ziepe.ca>
Jason Gunthorpe <jgg@ziepe•ca> writes:
>> And that brings us to the same point whether it’s better to return
>> the memory along with it’s state or we pass the requested state.
>> I think for other cases it’s fine for the device/DMA-API to dictate
>> the attrs, but not in restricted-dma case, the firmware just knows better.
>
> The memory type must be returned back at some level so downstream
> things can do the right transformation of the phys_addr_t.
>
> One of the aspirational CC things that should work is a T=1 device
> tries to DMA from a decrypted page, finds the address is above the dma
> limit of the device, so it bounces it with SWIOTLB to an encrypted low
> address page and then the DMA API internal flow switiches from working
> with decrypted to encrypted phys_addr_t.
>
> If we can make that work then maybe the flows are designed correctly.
>
That is what this patch series aims to do. dma_direct_map_phys() will
derive the DMA address based on the attributes of the physical address:
if (attrs & DMA_ATTR_CC_SHARED)
dma_addr = phys_to_dma_unencrypted(dev, phys);
else
dma_addr = phys_to_dma_encrypted(dev, phys);
If that fails the dma_capable() check, we fall back to swiotlb_map():
if (unlikely(!dma_capable(dev, dma_addr, size, true, attrs)))
return swiotlb_map(dev, phys, size, dir, attrs);
We currently do not have an encrypted SWIOTLB pool, but once that is
supported, swiotlb_map() should do the right thing and return the
correct encrypted dma_addr_t based on io_tlb_mem->unencrypted:
if (dev->dma_io_tlb_mem->unencrypted) {
dma_addr = phys_to_dma_unencrypted(dev, swiotlb_addr);
attrs |= DMA_ATTR_CC_SHARED;
} else {
dma_addr = phys_to_dma_encrypted(dev, swiotlb_addr);
}
-aneesh
next prev parent reply other threads:[~2026-05-14 6:24 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 9:03 [PATCH v4 00/13] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Aneesh Kumar K.V (Arm)
2026-05-12 9:03 ` [PATCH v4 01/13] dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages Aneesh Kumar K.V (Arm)
2026-05-13 13:57 ` Mostafa Saleh
2026-05-14 4:54 ` Aneesh Kumar K.V
2026-05-12 9:03 ` [PATCH v4 02/13] dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths Aneesh Kumar K.V (Arm)
2026-05-13 13:58 ` Mostafa Saleh
2026-05-14 5:01 ` Aneesh Kumar K.V
2026-05-12 9:03 ` [PATCH v4 03/13] dma-pool: track decrypted atomic pools and select them via attrs Aneesh Kumar K.V (Arm)
2026-05-13 14:00 ` Mostafa Saleh
2026-05-14 7:00 ` Aneesh Kumar K.V
2026-05-14 8:06 ` Mostafa Saleh
2026-05-16 12:53 ` Alexey Kardashevskiy
2026-05-18 8:19 ` Alexey Kardashevskiy
2026-05-18 8:32 ` Aneesh Kumar K.V
2026-05-12 9:03 ` [PATCH v4 04/13] dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-05-13 14:27 ` Mostafa Saleh
2026-05-13 17:24 ` Jason Gunthorpe
2026-05-14 6:24 ` Aneesh Kumar K.V [this message]
2026-05-14 11:48 ` Mostafa Saleh
2026-05-14 12:35 ` Jason Gunthorpe
[not found] ` <agXfm3mS_M3fvRrN@google.com>
2026-05-15 22:51 ` Jason Gunthorpe
2026-05-19 11:06 ` Mostafa Saleh
2026-05-19 13:39 ` Jason Gunthorpe
2026-05-14 5:54 ` Aneesh Kumar K.V
2026-05-14 12:02 ` Mostafa Saleh
2026-05-14 12:48 ` Aneesh Kumar K.V
2026-05-14 14:21 ` Mostafa Saleh
2026-05-14 14:43 ` Aneesh Kumar K.V
2026-05-19 11:04 ` Mostafa Saleh
2026-05-19 12:27 ` Aneesh Kumar K.V
2026-05-19 15:07 ` Aneesh Kumar K.V
2026-05-19 15:27 ` Jason Gunthorpe
2026-05-19 16:05 ` Aneesh Kumar K.V
2026-05-19 16:11 ` Jason Gunthorpe
2026-05-20 3:57 ` Aneesh Kumar K.V
2026-05-20 13:40 ` Jason Gunthorpe
2026-05-19 13:29 ` Jason Gunthorpe
2026-05-19 13:41 ` Mostafa Saleh
2026-05-19 14:00 ` Aneesh Kumar K.V
2026-05-19 14:04 ` Mostafa Saleh
2026-05-19 14:17 ` Aneesh Kumar K.V
2026-05-19 14:27 ` Mostafa Saleh
2026-05-19 14:37 ` Jason Gunthorpe
2026-05-19 14:35 ` Jason Gunthorpe
2026-05-19 14:45 ` Mostafa Saleh
2026-05-19 14:49 ` Jason Gunthorpe
2026-05-14 14:37 ` Jason Gunthorpe
2026-05-18 8:19 ` Alexey Kardashevskiy
2026-05-21 17:06 ` Mostafa Saleh
2026-05-21 17:20 ` Aneesh Kumar K.V
2026-05-12 9:04 ` [PATCH v4 05/13] dma-mapping: make dma_pgprot() " Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 06/13] dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 07/13] dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-05-18 10:04 ` Christian Borntraeger
2026-05-21 15:37 ` Aneesh Kumar K.V
2026-05-12 9:04 ` [PATCH v4 08/13] dma-direct: set decrypted flag for remapped DMA allocations Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 09/13] dma-direct: select DMA address encoding from DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 10/13] dma-pool: fix page leak in atomic_pool_expand() cleanup Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 11/13] dma-direct: rename ret to cpu_addr in alloc helpers Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 12/13] dma-direct: return struct page from dma_direct_alloc_from_pool() Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 13/13] x86/amd-gart: preserve the direct DMA address until GART mapping succeeds Aneesh Kumar K.V (Arm)
2026-05-21 11:54 ` Aneesh Kumar K.V
2026-05-17 6:19 ` [PATCH v4 00/13] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Jiri Pirko
2026-05-18 8:23 ` Aneesh Kumar K.V
2026-05-18 8:34 ` Jiri Pirko
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