From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [RFC PATCH v1 10/10] xen/arm: GICv3 device tree parsing Date: Mon, 24 Mar 2014 18:00:59 +0000 Message-ID: <533072DB.8040302@linaro.org> References: <1395238631-2024-1-git-send-email-vijay.kilari@gmail.com> <1395238631-2024-11-git-send-email-vijay.kilari@gmail.com> <532B127C.3030201@linaro.org> <1395661437.19365.66.camel@kazak.uk.xensource.com> <53301F0E.9030107@linaro.org> <53302023.3040502@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Stefano Stabellini Cc: Ian Campbell , Vijay Kilari , Prasun Kapoor , Vijaya Kumar K , xen-devel@lists.xen.org, Stefano Stabellini List-Id: xen-devel@lists.xenproject.org Hi Stefano, On 24/03/14 17:34, Stefano Stabellini wrote: > I think that for Dom0 we have to use vgic_v3, because it doesn't only > give you support for more vcpus but also MSI and MSI-X delivery. Right. > > For DomUs it might be important to support vgic_v2 on gicv3 hardware, > however I wouldn't want to defer the decision to the user (i.e. > introduce yet another VM config option), if not for debugging. > > Would it be possible to advirtise both gicv2 and gicv3 on device tree? > What would the guest kernel do in that case? Linux will try to load both GICv2 and GICv3 drivers. In any case I don't think it's a solution because: - you don't know how the kernel will react - how will you choose which backend to use? > Otherwise we could default to vgic_v2 if vcpus <= 8 and vgic_v3 if > vcpus > 8. What about kernel which only support GICv3 and have less than 8 VCPUS? What about of device (MSI, ...) passthrough with this kind of kernel? I think we need to have a VM config option in this specific case. Regards, -- Julien Grall