From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 1/7] KVM: api: add kvm_irq_routing_extended_msi Date: Mon, 6 Jul 2015 13:51:24 +0200 Message-ID: <559A6BBC.2040901@redhat.com> References: <1435592237-17924-1-git-send-email-eric.auger@linaro.org> <1435592237-17924-2-git-send-email-eric.auger@linaro.org> <011f01d0b498$6a17aeb0$3e470c10$@samsung.com> <5596503E.6040902@arm.com> <00fd01d0b7b6$f6cf3550$e46d9ff0$@samsung.com> <559A3C9C.6050302@arm.com> <20150706093026.GA11590@cbox> <559A52E6.5050402@arm.com> <20150706103755.GC11590@cbox> <559A6164.1000401@redhat.com> <559A6527.1040107@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <559A6527.1040107@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: Andre Przywara , Christoffer Dall Cc: Pavel Fedin , 'Eric Auger' , "eric.auger@st.com" , "linux-arm-kernel@lists.infradead.org" , Marc Zyngier , "kvmarm@lists.cs.columbia.edu" , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" List-Id: kvmarm@lists.cs.columbia.edu On 06/07/2015 13:23, Andre Przywara wrote: > Hi Paolo, > > thanks for looking at this! > > On 06/07/15 12:07, Paolo Bonzini wrote: >> >> >> On 06/07/2015 12:37, Christoffer Dall wrote: >>> I don't view it as 'the kernel requires this' but as 'the kernel will >>> not complain with arbitrary error code if you set the devid flag' >>> capability, and it's up to userspace (as usual) to provide the correct >>> arguments for things to work, and up to the kernel to ensure we don't >>> crash the system etc. >>> >>> Thus, if you want to advertise it as a capability, I would rather call >>> it KVM_CAP_MSI_DEVID. >> >> I agree. Does userspace know that ITS guests always require devid? > > Well, as we are about to implement this: yes. But the issue is that MSI > injection and GSI routing code is generic PCI code in userland (at least > in kvmtool, guess in QEMU, too), so I don't want to pull in any kind of > ARM specific code in there. The idea is to always provide the device ID > from the PCI code (for PCI devices it's just the B/D/F triplet), but > only send it to the kernel if needed. Querying a KVM capability is > perfectly fine for this IMO. Yes, I agree. Paolo