From mboxrd@z Thu Jan 1 00:00:00 1970 From: Don Slutz Subject: Re: [PATCH for 4.5 v7 1/1] Add mmio_hole_size Date: Tue, 21 Oct 2014 08:56:22 -0400 Message-ID: <544657F6.8000104@terremark.com> References: <1413204679-7345-1-git-send-email-dslutz@verizon.com> <1413204679-7345-2-git-send-email-dslutz@verizon.com> <20141014155622.GE30965@laptop.dumpdata.com> <20141015161242.GD29948@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20141015161242.GD29948@zion.uk.xensource.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: Wei Liu , Konrad Rzeszutek Wilk Cc: Ian Campbell , Stefano Stabellini , Ian Jackson , Don Slutz , xen-devel@lists.xen.org, Jan Beulich , Boris Ostrovsky List-Id: xen-devel@lists.xenproject.org On 10/15/14 12:12, Wei Liu wrote: > On Tue, Oct 14, 2014 at 11:56:22AM -0400, Konrad Rzeszutek Wilk wrote: >> On Mon, Oct 13, 2014 at 08:51:19AM -0400, Don Slutz wrote: >>> If you add enough PCI devices then all mmio may not fit below 4G >>> which may not be the layout the user wanted. This allows you to >>> increase the below 4G address space that PCI devices can use and >>> therefore in more cases not have any mmio that is above 4G. >>> >>> There are real PCI cards that do not support mmio over 4G, so if you >>> want to emulate them precisely, you may also need to increase the >>> space below 4G for them. There are drivers for these cards that also >>> do not work if they have their mmio space mapped above 4G. >>> >>> This allows growing the MMIO hole to the size needed. >>> >>> This may help with using pci passthru and HVM. >>> >>> Signed-off-by: Don Slutz >> >> Wei, Ian, Stefano, Ian, >> >> I am OK with this patch going in Xen 4.5 (as a release-manager) >> but it can't go anywhere unless there is an Ack/Review. >> >> P.S. >> Also added Wei to the CC list. > I didn't follow this closely. ISTR there's disagreement on whether this > is the correct approach to fix this bug. Have we reached consent that we > should use this approach? I was hoping that if someone did have a disagreement with this approach, they would have responded to this e-mail. As far as I know the only disagreement is on bug #28: #28 - support PCI hole resize in qemu-xen http://bugs.xenproject.org/xen/bug/28 since this approach is not supporting PCI hole resize in qemu-xen. > From Jan Beulich: >> From Don Slutz: >> The support for changing mmio_hole_size is still "missing" from QEMU. >> So this code only works for qemu-traditional. I think Jan said >> back on v1 or v2 (sorry, e-mail issues) that since this is a config, >> disable the auto changing code. > Because it didn't seem like you would want to properly take care > of both cases together (iirc the fact that the configured hole size > could be other than a power of 2 introduced a conflict with the > current resizing logic). I.e. doing one or the other is a suitable > first step imo, but with room for improvement. So I am going with this 1st step and not claiming to fix bug #28. -Don Slutz > Wei.