From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934645AbbEOPpz (ORCPT ); Fri, 15 May 2015 11:45:55 -0400 Received: from smtp.citrix.com ([66.165.176.89]:5939 "EHLO SMTP.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934709AbbEOPpv (ORCPT ); Fri, 15 May 2015 11:45:51 -0400 X-IronPort-AV: E=Sophos;i="5.13,434,1427760000"; d="scan'208";a="263121857" Message-ID: <555614AB.9000006@citrix.com> Date: Fri, 15 May 2015 16:45:47 +0100 From: David Vrabel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: Julien Grall , CC: , , , , , , , , Subject: Re: [Xen-devel] [RFC 00/23] arm64: Add support for 64KB page granularity in Xen guest References: <1431622863-28575-1-git-send-email-julien.grall@citrix.com> In-Reply-To: <1431622863-28575-1-git-send-email-julien.grall@citrix.com> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-DLP: MIA2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.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 From mboxrd@z Thu Jan 1 00:00:00 1970 From: david.vrabel@citrix.com (David Vrabel) Date: Fri, 15 May 2015 16:45:47 +0100 Subject: [Xen-devel] [RFC 00/23] arm64: Add support for 64KB page granularity in Xen guest In-Reply-To: <1431622863-28575-1-git-send-email-julien.grall@citrix.com> References: <1431622863-28575-1-git-send-email-julien.grall@citrix.com> Message-ID: <555614AB.9000006@citrix.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.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