From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: Requesting for freeze exception for ARM/ITS patches Date: Fri, 10 Jul 2015 17:07:29 +0100 Message-ID: <1436544449.10074.120.camel@citrix.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" 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: Vijay Kilari Cc: Wei Liu , Stefano Stabellini , Prasun Kapoor , manish.jaggi@caviumnetworks.com, "xen-devel@lists.xen.org" , Julien Grall , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On Fri, 2015-07-10 at 16:16 +0530, Vijay Kilari wrote: > I would like to have freeze exception for ITS feature on ARM64. > Design got freeze few weeks back and I have sent v4 version of patch series > today. Thanks, I've been through v4 and it is certainly much improved over v3. There are some smaller issues and one slightly more major one regarding the mechanisms used to inject a vlpi, which I hope I've explained fully enough in the review (in short if you do what the design draft says it should be fixed, the incorrectness and complexity is all down to trying to do things a different way which leads to you needing to lookup things which you shouldn't need to lookup in places where you don't need them) > This patches will not impact any generic code of other platforms and have minor > changes generic arm related code. Also these patches are only for > ARM64 platform. There is some stuff which touches the non-ITS related ARM interrupt handling, however they are mostly adding checks in is_lpi and in some cases alternative code if it is true, which should be pretty safe. As I mentioned during review care needs to be taken to ensure that this code is not enabled for any guest on a platform which has no ITS and to only enable it for dom0 on platforms which do. Due to the structure of the patch series (which is not optimised for being able to follow what is going on) it wasn't clear to me if this was the case, but I think not. There are no checks for dom0 and only checks for the presence of LPI/ITS in the physical gic, not as a property of the individual domains. When I say "not enabled" I mean no MMIO handlers registered, no GITS_TRANSLATER MMIO mapping to the guest, no functional change to the existing GIC* registers. > These patches are pre-requisite for PCI support / Pass-through support > on ARM64 platforms. As I explained in my reply to Jan I think this is underselling it a little, since AIUI it should make it possible to boot Xen on ThunderX and do useful things (like run guests). If you can get us a v5 with all of the issues I pointed out done _early_ next week then, with my ARM maintainers hat on, I think a freeze exception could be something which could then be something which could realistically be considered. However the final call on this belongs to Wei. Note I tried to apply this series to xen.git#staging and it had rejects, I think it was written against #master and will need rebasing. Please base v5 on #staging instead. Ian. > The risk is minor and as of today only used by Cavium ThunderX platform. > > Regards > Vijay