From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 71F902C02A3 for ; Tue, 18 Jun 2013 14:39:14 +1000 (EST) Message-ID: <1371530335.21896.169.camel@pasglop> Subject: Re: [PATCH 3/4] KVM: PPC: Add support for IOMMU in-kernel handling From: Benjamin Herrenschmidt To: Alex Williamson Date: Tue, 18 Jun 2013 14:38:55 +1000 In-Reply-To: <1371522772.22681.140.camel@ul30vt.home> References: <1370412673-1345-1-git-send-email-aik@ozlabs.ru> <1370412673-1345-4-git-send-email-aik@ozlabs.ru> <1371422343.21896.143.camel@pasglop> <1371438800.22681.38.camel@ul30vt.home> <1371441361.21896.152.camel@pasglop> <1371522772.22681.140.camel@ul30vt.home> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: kvm@vger.kernel.org, Alexey Kardashevskiy , Rusty Russell , Alexander Graf , kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, Paul Mackerras , linuxppc-dev@lists.ozlabs.org, David Gibson List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, 2013-06-17 at 20:32 -0600, Alex Williamson wrote: > Right, we don't want to create dependencies across modules. I don't > have a vision for how this should work. This is effectively a complete > side-band to vfio, so we're really just dealing in the iommu group > space. Maybe there needs to be some kind of registration of ownership > for the group using some kind of token. It would need to include some > kind of notification when that ownership ends. That might also be a > convenient tag to toggle driver probing off for devices in the group. > Other ideas? Thanks, All of that smells nasty like it will need a pile of bloody infrastructure.... which makes me think it's too complicated and not the right approach. How does access control work today on x86/VFIO ? Can you give me a bit more details ? I didn't get a good grasp in your previous email.... >>From the look of it, the VFIO file descriptor is what has the "access control" to the underlying iommu, is this right ? So we somewhat need to transfer (or copy) that ownership from the VFIO fd to the KVM VM. I don't see a way to do that without some cross-layering here... Rusty, are you aware of some kernel mechanism we can use for that ? Cheers, Ben.