From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 11A72311C15; Fri, 17 Jul 2026 13:42:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784295766; cv=none; b=cBXf6KnnpcJVWvUYLAm5dP8W3y8HMbOJDbdkFrPu9szYQXdQcVvr5T9tkvWdrB8d7AQNTqpac+IuzM/sjom+2nKLuHs+PL83E/hF2VPi6Voxf+G6uAPPU/4b7VURUVIqMgyoz3CZJKL/sA5DdLpWXUp2X4CEhG5jpflroLTI9jA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784295766; c=relaxed/simple; bh=lD/C55RPTNkAoWBALB4tsbeKSWOx57U5ia61Pk1caS4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=uEMbYMyIxSkECnhJYZ1iHqh9fcE1CJIWOPes7bIxZYChYK6GJAv7sZhaEFtmXkBw2nw0F6p+CU1Z+Hjq+BqGz6VlFVJRZNhBe0uOPav/alFtU3RLDYoTydg1y2GDnK1rfVw3p8o5C7VNC+L1RpQl+vjhMua0TbDzdscbfSFAN/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=O8IdS8G3; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="O8IdS8G3" 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 E9D111477; Fri, 17 Jul 2026 06:42:37 -0700 (PDT) Received: from [10.57.84.220] (unknown [10.57.84.220]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5B4AD3F7D8; Fri, 17 Jul 2026 06:42:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784295762; bh=lD/C55RPTNkAoWBALB4tsbeKSWOx57U5ia61Pk1caS4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=O8IdS8G3CnKuMNburYce3PCdi61FDsSRFopmQca85h5hKz29/iSlxtdvby8rVIIAj LtCuH1paFHjRXytQB5McfRZ0LM8i/XXM0l90zvuDgyK1HUw8k4i1yZJMQslVOOtuQG sg/V2vf8ELp7Z+iC2v+3/ef855u9qt/W5t28YTtk= Message-ID: <753239d6-af3b-48f1-b4bc-229ef9b6ed49@arm.com> Date: Fri, 17 Jul 2026 14:42:37 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 0/8] Arm Core Local Accelerator Driver Content-Language: en-GB To: Jason Gunthorpe , Will Deacon Cc: Greg Kroah-Hartman , Arnd Bergmann , Catalin Marinas , Mark Rutland , Jean-Philippe Brucker , Oded Gabbay , Jonathan Corbet , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, maz@kernel.org, oupton@kernel.org, hch@infradead.org References: <20260717104759.123203-1-ryan.roberts@arm.com> <20260717133200.GB699082@nvidia.com> From: Ryan Roberts In-Reply-To: <20260717133200.GB699082@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 17/07/2026 14:32, Jason Gunthorpe wrote: > On Fri, Jul 17, 2026 at 12:33:17PM +0100, Will Deacon wrote: > >> first. So, at the moment, this just looks like a burden to me, especially >> as it appears to create a brand new, device-specific UAPI for what is >> ostensibly a form of SVA - something which the community is actively >> working on already. > > Yeah, I think it was a mistake to hardwire the invalidation to the > CPU. It would fit much better into Linux if the invalidation was > separate and independently controllable with an option to follow the > CPU. Well I'm certainly not going to disagree, but the HW is somewhat fixed at this point :-| > > Then you could use a normal S2 page table through iommufd and not mess > with kvm. (though the VMID sharing with KVM for a BTM-like scheme was > never solved upstream) > > I also wouldn't expect you to use vfio-mdev, if the devices are > discovered and known at boot then it should be a normal vfio driver. OK good feedback - I'm not going to claim to be a VFIO expert (especially not in front of an actual VFIO expert) - We'll look closer at this and come back if we have questions (although unlikely over the summer holiday). Thanks, Ryan > > Jason