From: Jason Gunthorpe <jgg@ziepe.ca>
To: Alexey Kardashevskiy <aik@amd.com>
Cc: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>,
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>,
Mostafa Saleh <smostafa@google.com>,
Petr Tesarik <ptesarik@suse.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, Jiri Pirko <jiri@nvidia.com>,
Michael Kelley <mhklinux@outlook.com>,
"Cheloha, Scott" <Scott.Cheloha@amd.com>
Subject: Re: [PATCH v6 03/20] dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths
Date: Thu, 2 Jul 2026 11:47:29 -0300 [thread overview]
Message-ID: <20260702144729.GP7525@ziepe.ca> (raw)
In-Reply-To: <98800d21-18f6-44d6-9ba0-da9b77567d85@amd.com>
On Thu, Jul 02, 2026 at 10:25:16AM +1000, Alexey Kardashevskiy wrote:
> > > not externally available so I'll have to trick the DMA layer into
> > > using SWIOTLB (which is still all shared, right?) as I specifically
> > > want to skip page conversions. Setting low DMA mask won't guarantee
> > > that the DMA layer won't allocate a page outside of SWIOTLB and
> > > convert it. Manually do
> >
> > Why so particular?
>
> aahhh I missed "pre-". I need a way to get pre-shared pages for my
> sev-guest activities.
It sounds to me like you don't, what you are worried about is
optimizing the dma_alloc_coherent flow to avoid fragmentation and all
CC architetures require this optimization.
So I'm strongly against you trying to open code something in your
driver. Use the DMA API as-is. Propose general DMA API improvements to
reduce the fragmentation problem. It is a real problem.
Jason
next prev parent reply other threads:[~2026-07-02 14:48 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-04 8:39 [PATCH v6 00/20] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Aneesh Kumar K.V (Arm)
2026-06-04 8:39 ` [PATCH v6 01/20] s390: Expose protected virtualization through cc_platform_has() Aneesh Kumar K.V (Arm)
2026-06-06 0:34 ` JAEHOON KIM
2026-06-09 13:44 ` Catalin Marinas
2026-06-04 8:39 ` [PATCH v6 02/20] dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages Aneesh Kumar K.V (Arm)
2026-06-09 12:15 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 03/20] dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths Aneesh Kumar K.V (Arm)
2026-06-09 12:18 ` Petr Tesarik
2026-06-17 0:50 ` Alexey Kardashevskiy
2026-06-17 14:46 ` Aneesh Kumar K.V
2026-06-17 15:41 ` Jason Gunthorpe
2026-06-18 2:39 ` Alexey Kardashevskiy
2026-06-30 16:02 ` Jason Gunthorpe
2026-07-02 0:25 ` Alexey Kardashevskiy
2026-07-02 14:47 ` Jason Gunthorpe [this message]
2026-06-04 8:39 ` [PATCH v6 04/20] dma-pool: track decrypted atomic pools and select them via attrs Aneesh Kumar K.V (Arm)
2026-06-09 12:23 ` Petr Tesarik
2026-06-09 14:32 ` Jason Gunthorpe
2026-06-10 8:07 ` Aneesh Kumar K.V
2026-06-10 16:41 ` Jason Gunthorpe
2026-06-11 4:51 ` Aneesh Kumar K.V
2026-06-11 5:25 ` Aneesh Kumar K.V
2026-06-11 11:37 ` Jason Gunthorpe
2026-06-11 11:50 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 05/20] dma: swiotlb: pass mapping attributes by reference Aneesh Kumar K.V (Arm)
2026-06-09 12:21 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 06/20] dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-06-09 12:48 ` Petr Tesarik
2026-06-10 8:46 ` Aneesh Kumar K.V
2026-06-04 8:39 ` [PATCH v6 07/20] dma-mapping: make dma_pgprot() " Aneesh Kumar K.V (Arm)
2026-06-04 8:39 ` [PATCH v6 08/20] dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks Aneesh Kumar K.V (Arm)
2026-06-09 12:50 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 09/20] dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-06-04 8:39 ` [PATCH v6 10/20] dma-direct: set decrypted flag for remapped DMA allocations Aneesh Kumar K.V (Arm)
2026-06-04 8:39 ` [PATCH v6 11/20] dma-direct: select DMA address encoding from DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-06-04 8:39 ` [PATCH v6 12/20] dma-pool: fix page leak in atomic_pool_expand() cleanup Aneesh Kumar K.V (Arm)
2026-06-04 8:39 ` [PATCH v6 13/20] dma-direct: rename ret to cpu_addr in alloc helpers Aneesh Kumar K.V (Arm)
2026-06-09 12:54 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 14/20] dma-direct: return struct page from dma_direct_alloc_from_pool() Aneesh Kumar K.V (Arm)
2026-06-09 13:12 ` Petr Tesarik
2026-06-09 13:45 ` Catalin Marinas
2026-06-09 14:15 ` Jason Gunthorpe
2026-06-04 8:39 ` [PATCH v6 15/20] iommu/dma: Check atomic pool allocation result directly Aneesh Kumar K.V (Arm)
2026-06-09 13:13 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 16/20] dma: swiotlb: free dynamic pools from process context Aneesh Kumar K.V (Arm)
2026-06-09 13:23 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 17/20] dma: swiotlb: handle set_memory_decrypted() failures Aneesh Kumar K.V (Arm)
2026-06-09 13:32 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 18/20] dma: free atomic pool pages by physical address Aneesh Kumar K.V (Arm)
2026-06-04 8:39 ` [PATCH v6 19/20] swiotlb: Preserve allocation virtual address for dynamic pools Aneesh Kumar K.V (Arm)
2026-06-09 13:40 ` Petr Tesarik
2026-06-04 8:39 ` [PATCH v6 20/20] swiotlb: remove unused SWIOTLB_FORCE flag Aneesh Kumar K.V (Arm)
2026-06-09 13:44 ` Petr Tesarik
2026-06-09 13:43 ` [PATCH v6 00/20] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Catalin Marinas
2026-06-09 14:47 ` Jason Gunthorpe
2026-06-18 4:44 ` Alexey Kardashevskiy
2026-06-18 8:37 ` Aneesh Kumar K.V
2026-06-18 15:37 ` Jason Gunthorpe
2026-06-19 2:05 ` Alexey Kardashevskiy
2026-06-19 12:03 ` Jason Gunthorpe
2026-06-19 13:44 ` Aneesh Kumar K.V
2026-06-22 0:58 ` Alexey Kardashevskiy
2026-06-30 16:18 ` Jason Gunthorpe
2026-06-19 12:14 ` Aneesh Kumar K.V
2026-06-19 12:21 ` Jason Gunthorpe
2026-06-19 13:36 ` Aneesh Kumar K.V
2026-06-19 14:06 ` Jason Gunthorpe
2026-06-29 6:46 ` Aneesh Kumar K.V
2026-06-29 9:51 ` Aneesh Kumar K.V
2026-06-30 17:42 ` Jason Gunthorpe
2026-07-01 3:09 ` Aneesh Kumar K.V
2026-07-02 15:19 ` Jason Gunthorpe
2026-07-02 1:04 ` Alexey Kardashevskiy
2026-06-11 5:52 ` Aneesh Kumar K.V
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