From: "Christian König" <christian.koenig@amd.com>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
"Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>,
linux-coco@lists.linux.dev, kvmarm@lists.linux.dev,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, iommu@lists.linux.dev,
Marc Zyngier <maz@kernel.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Robin Murphy <robin.murphy@arm.com>,
Steven Price <steven.price@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Thomas Gleixner <tglx@kernel.org>, Will Deacon <will@kernel.org>,
Sumit Semwal <sumit.semwal@linaro.org>,
"T.J. Mercier" <tjmercier@google.com>
Subject: Re: [PATCH v6 7/9] dma-buf: system_heap: Enforce shared-granule alignment for cc-shared buffers
Date: Mon, 21 Sep 2026 11:07:17 +0200 [thread overview]
Message-ID: <6115eaf7-21bc-49ce-8a74-08fd37a1e2c9@amd.com> (raw)
In-Reply-To: <20260918165315.GF11599@ziepe.ca>
On 9/18/26 18:53, Jason Gunthorpe wrote:
> On Fri, Sep 18, 2026 at 05:39:55PM +0200, Christian König wrote:
>
>>> Arch code can figure out how to do it. If some ARM configs only give
>>> order 4 folios or whatever then dmabuf heap doesn't care.
>>
>> The fundamental problem is that DMA allocations are highly
>> architecture and device specific while Linux memory allocation APIs
>> are generic.
>
> This isn't a dma allocation, this is a memory allocation.
No, I mean this is a DMA-buf heaps allocation. It is a DMA allocation, we just don't know for which device.
So ideally we should use resources which work for most devices in the system. If a device has special allocation requirements (CMA, restricted addressing etc...) we need a specialized DMA-buf heaps for it.
That userspace provides this cc_shared flag is a NO-GO to begin with.
Regards,
Christian.
> We made things so the CC shared folios are DMA mappable through the
> DMA API. From the heap perspective the only difference is passing an
> additional DMA_ATTR_CC_SHARED when DMA mapping the folio.
>
> Jason
next prev parent reply other threads:[~2026-09-21 9:07 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 10:34 [PATCH v6 0/9] coco: guest: Enforce host page-size alignment for shared buffers Aneesh Kumar K.V (Arm)
2026-09-04 10:34 ` [PATCH v6 1/9] mm/mem_encrypt: Add helpers for shared-buffer alignment Aneesh Kumar K.V (Arm)
2026-09-04 10:34 ` [PATCH v6 2/9] irqchip/gic-v3-its: Align shared ITS allocations to the CoCo shared granule size Aneesh Kumar K.V (Arm)
2026-09-04 10:34 ` [PATCH v6 3/9] dma-mapping: Pass allocation attrs to contiguous allocation helpers Aneesh Kumar K.V (Arm)
2026-09-04 10:34 ` [PATCH v6 4/9] dma-direct: Align CoCo shared DMA allocations to the shared granule size Aneesh Kumar K.V (Arm)
2026-09-18 14:16 ` Catalin Marinas
2026-09-04 10:34 ` [PATCH v6 5/9] swiotlb: Align shared IO TLB pools " Aneesh Kumar K.V (Arm)
2026-09-04 10:34 ` [PATCH v6 6/9] swiotlb: Reject misaligned restricted DMA pools for CoCo guests Aneesh Kumar K.V (Arm)
2026-09-04 10:34 ` [PATCH v6 7/9] dma-buf: system_heap: Enforce shared-granule alignment for cc-shared buffers Aneesh Kumar K.V (Arm)
2026-09-18 15:16 ` Catalin Marinas
2026-09-18 15:23 ` Christian König
2026-09-18 15:36 ` Jason Gunthorpe
2026-09-18 15:39 ` Christian König
2026-09-18 16:53 ` Jason Gunthorpe
2026-09-21 9:07 ` Christian König [this message]
2026-09-21 11:51 ` Jason Gunthorpe
2026-09-21 12:05 ` Christian König
2026-09-21 12:17 ` Jason Gunthorpe
2026-09-21 12:24 ` Christian König
2026-09-21 12:37 ` Jason Gunthorpe
2026-09-21 15:26 ` Aneesh Kumar K.V
2026-09-19 14:57 ` Aneesh Kumar K.V
2026-09-19 21:35 ` Jason Gunthorpe
2026-09-20 7:24 ` Aneesh Kumar K.V
2026-09-21 6:57 ` Aneesh Kumar K.V
2026-09-04 10:34 ` [PATCH v6 8/9] arm64: realm: Add RHI helper to query IPA state change alignment Aneesh Kumar K.V (Arm)
2026-09-16 16:12 ` Suzuki K Poulose
2026-09-18 10:39 ` Aneesh Kumar K.V
2026-09-04 10:34 ` [PATCH v6 9/9] arm64: realm: Expose the CCA shared granule size through mem_encrypt ops Aneesh Kumar K.V (Arm)
2026-09-16 16:17 ` Suzuki K Poulose
2026-09-18 16:52 ` [PATCH v6 0/9] coco: guest: Enforce host page-size alignment for shared buffers Catalin Marinas
2026-09-18 16:57 ` Jason Gunthorpe
2026-09-18 17:10 ` Catalin Marinas
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