Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754489AbbGFLHZ (ORCPT ); Mon, 6 Jul 2015 07:07:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44320 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754040AbbGFLHX (ORCPT ); Mon, 6 Jul 2015 07:07:23 -0400 Subject: Re: [PATCH 1/7] KVM: api: add kvm_irq_routing_extended_msi To: Christoffer Dall , Andre Przywara 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> 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" From: Paolo Bonzini Message-ID: <559A6164.1000401@redhat.com> Date: Mon, 6 Jul 2015 13:07:16 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.0.1 MIME-Version: 1.0 In-Reply-To: <20150706103755.GC11590@cbox> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1277 Lines: 30 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? I guess it's okay to return -EINVAL if the userspace doesn't set the flag but the virtual hardware requires it. Paolo > The question is if userspace code that sets the devid flag will anyway > depend on some discovery mechanism of whether or not the kernel supports > arm64 irqfd etc. and if so, can we be sure to add the required support > at once in the kernel so that EINVAL never means 'you set the flags > field on the ioctl on an old kernel'? > > This smells an awful lot like a capability to me. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/