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b=kN3DxXhiV6A32AfRhNBQCO8Y9H3rbjoYrVAP4Y+RwnGiaH2R4moCILniw2BNmc07i qVDB2xKU0IDVgY36eMntlSkuzEBYinOGgCSE0qA/VEzpbfJWamjWYMHLWeJVGM2Q6c TT41noYxnIJu2mycFyI4SXwKJL3jDjmL5dWuupLA= Received: from eusmtip2.samsung.com (unknown [203.254.199.222]) by eucas1p1.samsung.com (KnoxPortal) with ESMTPA id 20260810113713eucas1p1b0aa58555e68eca16ad8962462d5afdd~Kbp9wCQhp2359123591eucas1p1b; Mon, 10 Aug 2026 11:37:13 +0000 (GMT) Received: from [106.120.50.46] (unknown [106.120.50.46]) by eusmtip2.samsung.com (KnoxPortal) with ESMTPA id 20260810113711eusmtip2ac80bb2608e56255c84c347422994fd6~Kbp8OmsY60892908929eusmtip2X; Mon, 10 Aug 2026 11:37:11 +0000 (GMT) Message-ID: <28442500-1d53-4776-bae5-459c3ffc1cc6@samsung.com> Date: Mon, 10 Aug 2026 13:37:11 +0200 MIME-Version: 1.0 User-Agent: Betterbird (Windows) Subject: Re: [PATCH] arm64: swiotlb: Keep the default size for protected guests To: Will Deacon , "Aneesh Kumar K.V" Cc: Jason Gunthorpe , Mostafa Saleh , iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org Content-Language: en-US From: Marek Szyprowski In-Reply-To: Content-Transfer-Encoding: 8bit X-CMS-MailID: 20260810113713eucas1p1b0aa58555e68eca16ad8962462d5afdd X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20260807182023eucas1p1f653436207b2b00338e99ea1d8f847df X-EPHeader: CA X-CMS-RootMailID: 20260807182023eucas1p1f653436207b2b00338e99ea1d8f847df References: <20260807135810.GA200537@ziepe.ca> <20260807164734.GE200537@ziepe.ca> <20260807182017.GH200537@ziepe.ca> <7d22482f-d5fd-4cf4-9d32-6a54e02f2fbb@samsung.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260810_043719_541357_1B0A51CF X-CRM114-Status: GOOD ( 19.96 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 10.08.2026 12:20, Will Deacon wrote: > On Mon, Aug 10, 2026 at 02:59:42PM +0530, Aneesh Kumar K.V wrote: >> Marek Szyprowski writes: >> >>> On 07.08.2026 20:20, Jason Gunthorpe wrote: >>>> On Fri, Aug 07, 2026 at 06:13:49PM +0000, Mostafa Saleh wrote: >>>>> But the whole thing is best effort anyway, the kernel picks >>>>> IO_TLB_DEFAULT_SIZE which does not depend on the system topology or >>>>> how many devices or how much DMA they do. >>>>> SWIOTLB memory is wasted if unused so we should be careful around >>>>> that as it would be the other way around and users would have to >>>>> decrease it manually. >>>> Yeah, it is why the arch code shouldn't really be sizing it directly, >>>> it should be done in common code and, yes, we are probably going to >>>> have to do something alot smarter to have the common code better >>>> auto-tune this for the CC case.. >>> What about the $subject patch? I assume that it is still needed to >>> >>> restore the behavior that was altered by the "[PATCH v8 00/23] >>> >>> dma-mapping: Track shared DMA state through direct, pool and swiotlb >>> >>> paths?" patchset? >>> >> I would request that we pick this patch to fix the regression described >> in https://lore.kernel.org/all/yq5azeyxyfol.fsf@kernel.org/. > I really don't think we need it. CCA hardware isn't exactly widespread > and the KVM host side patches don't appear close to being merged. Does this mean that the branch for-next/coco [1] won't go to v7.3-rc1? I've used it as a base for the mentioned DMA-mapping patchset. [1] https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/log/?h=for-next/coco > We have time to fix this properly, rather than papering over it in the > arch code. > > Please consider this a NAK from the arm64 side on this patch. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland