Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754721AbbGFPit (ORCPT ); Mon, 6 Jul 2015 11:38:49 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:51944 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753047AbbGFPid (ORCPT ); Mon, 6 Jul 2015 11:38:33 -0400 Subject: Re: [PATCH 1/7] KVM: api: add kvm_irq_routing_extended_msi To: Pavel Fedin , "'Paolo Bonzini'" , "'Christoffer Dall'" 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> <559A6BBC.2040901@redhat.com> <024301d0b7f0$2b13b410$813b1c30$@samsung.com> Cc: "'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: Andre Przywara X-Enigmail-Draft-Status: N1110 Organization: ARM Ltd. Message-ID: <559AA0D6.7070703@arm.com> Date: Mon, 6 Jul 2015 16:37:58 +0100 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: <024301d0b7f0$2b13b410$813b1c30$@samsung.com> 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: 2917 Lines: 87 Hi Pavel, On 06/07/15 14:32, Pavel Fedin wrote: > Hi! > >>> 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. > > Actually, we already have this capability, it's KVM_CAP_IRQ_ROUTING. If we have this capability, > and want to use irqfds with GICv3, we need to set KVM_MSI_VALID_DEVID. This is the connection that I don't like: We make the decision to support a flag on a generic KVM interface dependent on some particular device emulation (for some very specific architecture, also). > And there is no other way to > use irqfds with GICv3. For now: yes, but I fail to see why the GICv3 is so special that is justifies an extra handling in the KVM interrupt routing code. If it is special, lets name it explicitly why: we need a device ID. > Just for example, this is what i have done in qemu: > --- cut --- > int kvm_irqchip_add_msi_route(KVMState *s, MSIMessage msg, PCIDevice *dev) > { > struct kvm_irq_routing_entry kroute = {}; > int virq; > > if (kvm_gsi_direct_mapping()) { > return kvm_arch_msi_data_to_gsi(msg.data); > } > > if (!kvm_gsi_routing_enabled()) { > return -ENOSYS; > } > > virq = kvm_irqchip_get_virq(s); > if (virq < 0) { > return virq; > } > > kroute.gsi = virq; > kroute.type = KVM_IRQ_ROUTING_MSI; > kroute.u.msi.address_lo = (uint32_t)msg.address; > kroute.u.msi.address_hi = msg.address >> 32; > kroute.u.msi.data = le32_to_cpu(msg.data); > kroute.flags = kvm_msi_flags; > if (kroute.flags & KVM_MSI_VALID_DEVID) { > kroute.u.msi.devid = (pci_bus_num(dev->bus) << 8) | dev->devfn; > } Wouldn't: if (kvm_vm_check_extension(s, KVM_CAP_MSI_DEVID)) { kroute.flags = KVM_MSI_VALID_DEVID; kroute.u.msi.devid = (pci_bus_num(dev->bus) << 8) | dev->devfn; } be saner (without a global variable)? That would make the interface more consistent, with a new flag being protected by a new capability. Cheers, Andre. > if (kvm_arch_fixup_msi_route(&kroute, msg.address, msg.data)) { > kvm_irqchip_release_virq(s, virq); > return -EINVAL; > } > > kvm_add_routing_entry(s, &kroute); > kvm_irqchip_commit_routes(s); > > return virq; > } -- 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/