From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 78D69CA5FF1 for ; Wed, 7 Oct 2026 11:13:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=AU1eKQiGl7gA1sBI3iY3LWJqXSK04Ffx5xbqGqLQtSA=; b=0zC1F+1BNOtrwF UYhLHk7ToKSc6ImbsVlXFDfr+h8Q4K0f9WX9weFqxp/KdhCOb55wAE0D7tKBF4hHbiYL7LvckFk/t Z0pC/QlNw0Axwro0XQgX7jv1jIbK55ZNDrOh9n2u2Fkzg1NYr38rMU+7yGaROkRN7namNb6KZKWDE Ce0dG500aMan1SKvCAlRKs1u93PG31SN1XQ+9dtwuBWxnpm4LXHW1B4b7ygUSSHK1SFkJJpJKhweg wiYvYoGz5QOhYDQVrbUcLKzKkVoUqduEnHoIj3oW1Nn7r2dyqQHxHyky6zQGCqbSwD5+WSVm4IZBc AMpqz26/Gi7xvQZzSUnw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xEPaZ-00000002Hd8-1fmN; Wed, 07 Oct 2026 11:13:35 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xEPaW-00000002HbW-2TNl; Wed, 07 Oct 2026 11:13:34 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 72249152B; Wed, 7 Oct 2026 04:13:27 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 582333F66F; Wed, 7 Oct 2026 04:13:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1791371610; bh=XkPVGrUWVDU6Wer3sPwtuoNfUx3GZi0QoXy/izLzVhE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=igUveoCg91F1QZl6TCWGQXum8trlGIS+yJnnGXsR+anmFKmTZ1B9TBQsyFhsbvTr3 8LWHLfx0Csp/j+Uam2n55lceRPr9TQ6wTKf+Lwm9q7pLVb3aBVKndMODvi3zPKvm0V t+PIIdBd0ff3Gzs8GCEjofEnDKdb1Cf+a6Zffw4w= Date: Wed, 7 Oct 2026 12:13:20 +0100 From: Catalin Marinas To: Will Deacon Cc: "Aneesh Kumar K.V (Arm)" , iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Robin Murphy , Marek Szyprowski , Jonathan Corbet , Shuah Khan , Randy Dunlap , Mark Rutland , Marc Zyngier , Steven Price , Suzuki K Poulose , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Petr Tesarik , Alexey Kardashevskiy , Dan Williams , Xu Yilun , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , Stefano Stabellini , Russell King , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , Jiaxun Yang , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH v6 6/8] dma: swiotlb: Centralize memory-encryption pool sizing Message-ID: References: <20260924060756.1325156-1-aneesh.kumar@kernel.org> <20260924060756.1325156-7-aneesh.kumar@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261007_041332_744024_83BE962C X-CRM114-Status: GOOD ( 25.73 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Wed, Oct 07, 2026 at 11:43:06AM +0100, Will Deacon wrote: > On Wed, Oct 07, 2026 at 11:04:05AM +0100, Catalin Marinas wrote: > > On Tue, Oct 06, 2026 at 10:49:17PM +0100, Will Deacon wrote: > > > On Thu, Sep 24, 2026 at 11:37:54AM +0530, Aneesh Kumar K.V (Arm) wrote: > > > > @@ -496,7 +516,8 @@ swiotlb_select_pool_policy(unsigned int flags) > > > > if (swiotlb_force_disable) > > > > return SWIOTLB_POOL_NONE; > > > > > > > > - if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) > > > > + if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) && > > > > + !restricted_dma_pool_present) > > > > return SWIOTLB_POOL_CC_GUEST; > > > > > > I think this check on the restricted DMA pool is too general -- the pool > > > could be tied to a specific DMA-capable peripheral and so treating its > > > presence as a global property isn't right. [...] > > That said, such heuristics should have been a separate patch to make it > > easier to review/drop. > > I think the only right way to get a semi-accurate heuristic is to take > into account the set of dma-capable devices that will use the swiotlb > pool, but that's fiddly and should probably be tackled as a separate > series. Maybe a simpler hack in that direction would be to take the > SWIOTLB_POOL_CC_GUEST if _any_ device is going to use swiotlb? You'll > run into the usual problem of not being able to tell if a device is > DMA-capable or not, but you could probably look for a global restricted > DMA pool and, if that doesn't exist, check for per-device restricted pools > on dma-coherent devices (since restricted DMA isn't supported by ACPI) as > a reasonable approximation. Yes, I think that's reasonable. We'd need to drive this from the arch code or, as you suggested, drivers/virt/coco rather than generic heuristics in the swiotlb code. -- Catalin _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv