From: Leon Romanovsky <leon@kernel.org>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: "Aneesh Kumar K.V" <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>,
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Mostafa Saleh <smostafa@google.com>,
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Xu Yilun <yilun.xu@linux.intel.com>,
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Michael Kelley <mhklinux@outlook.com>
Subject: Re: [PATCH v8 01/23] dma-direct: return struct page from dma_direct_alloc_from_pool()
Date: Mon, 27 Jul 2026 14:40:15 +0300 [thread overview]
Message-ID: <20260727114015.GL12003@unreal> (raw)
In-Reply-To: <ambdXXcfgK+cxqxa@ziepe.ca>
On Mon, Jul 27, 2026 at 01:23:57AM -0300, Jason Gunthorpe wrote:
> On Sun, Jul 26, 2026 at 11:17:53AM +0300, Leon Romanovsky wrote:
>
> > Currently, the phys type universally describes memory and can be
> > reliably translated into any required representation. It is the most
> > fundamental type we have.
>
> You cannot go from phys to page reliably unless you make assumptions
> about the phys, that's the whole issue here. If the callchain expects
> and intends to use a page it should really stay in a page and not take
> a side trip to phys.
>
> I agree it would help to have some helpers that were more phys based
> for the callchains that want that since we are mixing two fairly
> different activities in these functions..
Yes, we are agreed here.
>
> But making phys the only output out of the pool isn't going to be an
> improvement.
I don't know, phys was natural suggestion due to multiple
page_to_phys/phys_to_page conversions down the road.
>
> BTW how does a struct page even work for decrypted memory? You can't
> actually use it that way right? If you try to access it then you'll
> get the wrong IPA and it should explode?
>
> Maybe we should be blocking the struct page path entirely for CC
> shared?
It will simplify things. Ultimately, this series demonstrates that
CC users must be aware of the memory attribute (CC_SHARED) and struct
page is too generic.
Thanks
>
> Jason
>
next prev parent reply other threads:[~2026-07-27 11:40 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-17 18:04 [PATCH v8 00/23] dma-mapping: Track shared DMA state through direct, pool and swiotlb paths Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 01/23] dma-direct: return struct page from dma_direct_alloc_from_pool() Aneesh Kumar K.V (Arm)
2026-07-21 11:54 ` Leon Romanovsky
2026-07-21 14:20 ` Aneesh Kumar K.V
2026-07-21 14:29 ` Leon Romanovsky
2026-07-21 15:10 ` Aneesh Kumar K.V
2026-07-21 15:33 ` Leon Romanovsky
2026-07-22 19:59 ` Jason Gunthorpe
2026-07-23 7:57 ` Leon Romanovsky
2026-07-25 14:34 ` Jason Gunthorpe
2026-07-26 8:17 ` Leon Romanovsky
2026-07-27 4:23 ` Jason Gunthorpe
2026-07-27 11:40 ` Leon Romanovsky [this message]
2026-07-17 18:04 ` [PATCH v8 02/23] dma-pool: fix page leak in atomic_pool_expand() cleanup Aneesh Kumar K.V (Arm)
2026-07-21 12:31 ` Leon Romanovsky
2026-07-21 14:41 ` Aneesh Kumar K.V
2026-07-21 15:34 ` Leon Romanovsky
2026-07-17 18:04 ` [PATCH v8 03/23] iommu/dma: Check atomic pool allocation result directly Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 04/23] dma: free atomic pool pages by physical address Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 05/23] swiotlb: Preserve allocation virtual address for dynamic pools Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 06/23] s390: Expose protected virtualization through cc_platform_has() Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 07/23] dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 08/23] coco: arm64: s390: powerpc: Mark secure guests with CC_ATTR_GUEST_MEM_ENCRYPT Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 09/23] dma-mapping: Add internal shared allocation attribute Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 10/23] dma-direct: use __DMA_ATTR_ALLOC_CC_SHARED in alloc/free paths Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 11/23] dma-pool: track decrypted atomic pools and select them via attrs Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 12/23] dma: swiotlb: pass mapping attributes by reference Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 13/23] dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 14/23] dma-mapping: make dma_pgprot() honor __DMA_ATTR_ALLOC_CC_SHARED Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 15/23] dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 16/23] dma-direct: Move dma_direct_map_phys() to dma/direct.c Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 17/23] dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 18/23] dma-direct: set decrypted flag for remapped DMA allocations Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 19/23] dma-direct: select DMA address encoding from __DMA_ATTR_ALLOC_CC_SHARED Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 20/23] dma-direct: rename ret to cpu_addr in alloc helpers Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 21/23] dma: swiotlb: free dynamic pools from process context Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 22/23] dma: swiotlb: handle set_memory_decrypted() failures Aneesh Kumar K.V (Arm)
2026-07-17 18:04 ` [PATCH v8 23/23] swiotlb: remove unused SWIOTLB_FORCE flag Aneesh Kumar K.V (Arm)
2026-07-21 12:40 ` [PATCH v8 00/23] dma-mapping: Track shared DMA state through direct, pool and swiotlb paths Leon Romanovsky
2026-07-22 19:57 ` Jason Gunthorpe
2026-07-23 7:51 ` Leon Romanovsky
2026-07-25 14:32 ` Jason Gunthorpe
2026-07-25 7:09 ` Aneesh Kumar K.V
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