From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [RFC 00/23] arm64: Add support for 64KB page granularity in Xen guest Date: Fri, 15 May 2015 16:45:47 +0100 Message-ID: <555614AB.9000006__2802.52478919483$1431704859$gmane$org@citrix.com> References: <1431622863-28575-1-git-send-email-julien.grall@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YtHoA-0001yf-MS for xen-devel@lists.xenproject.org; Fri, 15 May 2015 15:45:54 +0000 In-Reply-To: <1431622863-28575-1-git-send-email-julien.grall@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Julien Grall , xen-devel@lists.xenproject.org Cc: wei.liu2@citrix.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, tim@xen.org, linux-kernel@vger.kernel.org, david.vrabel@citrix.com, boris.ostrovsky@oracle.com, linux-arm-kernel@lists.infradead.org, roger.pau@citrix.com List-Id: xen-devel@lists.xenproject.org On 14/05/15 18:00, Julien Grall wrote: > Hi all, > > ARM64 Linux is supporting both 4KB and 64KB page granularity. Although, Xen > hypercall interface and PV protocol are always based on 4KB page granularity. > > Any attempt to boot a Linux guest with 64KB pages enabled will result to a > guest crash. > > This series is a first attempt to allow those Linux running with the current > hypercall interface and PV protocol. > > This solution has been chosen because we want to run Linux 64KB in released > Xen ARM version or/and platform using an old version of Linux DOM0. The key problem I see with this approach is the confusion between guest page size and Xen page size. This is going to be particularly problematic since the majority of development/usage will remain on x86 where PAGE_SIZE == XEN_PAGE_SIZE. I think it would be nice to keep XEN_PAGE_SIZE etc out of front and backend drivers. Perhaps with a suitable set of helper functions? David