From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Auger Subject: Re: [RFC 0/6] KVM: arm/arm64: gsi routing support Date: Mon, 22 Jun 2015 10:31:16 +0200 Message-ID: <5587C7D4.2010408@linaro.org> References: <1434649258-27065-1-git-send-email-eric.auger@linaro.org> <011e01d0aa5a$6b14fae0$413ef0a0$@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id BF94655DA1 for ; Mon, 22 Jun 2015 04:20:49 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id f8Ym1P+bc7K9 for ; Mon, 22 Jun 2015 04:20:48 -0400 (EDT) Received: from mail-wg0-f45.google.com (mail-wg0-f45.google.com [74.125.82.45]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 7736455C7F for ; Mon, 22 Jun 2015 04:20:48 -0400 (EDT) Received: by wgck11 with SMTP id k11so7345227wgc.0 for ; Mon, 22 Jun 2015 01:31:38 -0700 (PDT) In-Reply-To: <011e01d0aa5a$6b14fae0$413ef0a0$@samsung.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: Pavel Fedin , eric.auger@st.com, christoffer.dall@linaro.org, marc.zyngier@arm.com, andre.przywara@arm.com, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org Cc: patches@linaro.org List-Id: kvmarm@lists.cs.columbia.edu Hi Pavel, On 06/19/2015 08:37 AM, Pavel Fedin wrote: > Hello! > >> The series therefore allows and mandates the usage of KVM_SET_GSI_ROUTING >> ioctl along with KVM_IRQFD. If the userspace does not define any routing >> table, no irqfd injection can happen. The user-space can use >> KVM_CAP_IRQ_ROUTING to detect whether a routing table is needed. > > Yesterday, half-sleeping in the train back home, i've got a simple idea how to resolve > conflicts with existing static GSI->SPI routing without bringing in any more > inconsistencies. > So far, in current implementation GSI is an SPI index (let alone KVM_IRQ_LINE, because > it's already another story on ARM). In order to maintain this convention we could simply > implement default routing which sets all GSIs to corresponding SPI pins. So, if the > userland never cares about KVM_SET_GSI_ROUTING, everything works as before. But it will be > possible to re-route GSIs to MSI. It will perfectly work because SPI signaling is used > with GICv2m, and MSI with GICv3(+), which cannot be used at the same time. I agree with you and I suggested the same approach in my cover letter. Since applying GSI routing to KVM_IRQ_LINE is quite problematic, I would be also in favour to forbid userspace GSI routing setting and implement it kernel-side. Userspace would only be allowed to define MSI routing entries. I will respin accordingly and validate it further with qemu. Best Regards Eric > > Kind regards, > Pavel Fedin > Expert Engineer > Samsung Electronics Research center Russia > >