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: Tue, 25 Mar 2014 12:34:24 +0000 Message-ID: <533177D0.8060609@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> <533072DB.8040302@linaro.org> <533177AA.1030504@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <533177AA.1030504@linaro.org> 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 On 03/25/2014 12:33 PM, Julien Grall wrote: > On 03/25/2014 11:04 AM, Stefano Stabellini wrote: >> On Mon, 24 Mar 2014, Julien Grall wrote: >>> 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. >> >> Having a VM config option is OK, but it should be the last resort for >> people doing something very uncommon. >> >> GICv3 support in Linux and distros is probably going to be widespread >> soon, so we might not have to worry about it though. > > I don't think GICv3 will supported in 3.15. The current series doesn't > support GICv3 on 32 bits > (http://www.spinics.net/lists/arm-kernel/msg317028.html). > > But, I'm more worry about other OS than Linux (e.g FreeRTOS, *BSD,...) > which may not support GICv2 before a while. I should have write GICv3. -- Julien Grall