From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yosuke Iwamatsu Subject: Re: Question about MMIO Region Alignment for PCI Pass-through Date: Wed, 12 Mar 2008 20:48:57 +0900 Message-ID: <47D7C329.2060706@ab.jp.nec.com> References: <47CE68F2.4070007@ab.jp.nec.com> <9392A06CB0FDC847B3A530B3DC174E7B04D3ED22@mse10be1.mse10.exchange.ms> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <9392A06CB0FDC847B3A530B3DC174E7B04D3ED22@mse10be1.mse10.exchange.ms> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: barak@neocleus.com Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Hi Barak, Thank you for your reply. Barak Fargoun wrote: > Hi! > > I have created the 'pci-mem-align' patch. The version posted before, had > some bugs. However, I have fixed those issues, and it works fine for me > now. What kinds of bugs did you fix? It would be nice if I could see your new patch. > BTW, why are you interested in this? Because I'm recently working a bit on PV PCI passthrough. I haven't encountered the mmio region conflict yet, but I think it is a a potential problem for all the passthrough methods (VT-d/IOMMU, PV driver domain and nativedom). Regards, ------------------ Yosuke Iwamatsu > > Barak > > -----Original Message----- > From: xen-devel-bounces@lists.xensource.com > [mailto:xen-devel-bounces@lists.xensource.com] On Behalf Of Yosuke > Iwamatsu > Sent: Wednesday, March 05, 2008 11:34 AM > To: xen-devel@lists.xensource.com > Subject: [Xen-devel] Question about MMIO Region Alignment for > PCIPass-through > > Hi there, > > I have a question about the mmio region access of PCI pass-trough > devices. > > When assigning a PCI device to a guest, pages that contain the device > mmio regions are mapped to the guest. Then the guest can directly issue > mmio instructions. However, there is a problem that, if a single page > has mmio regions of multiple devices, we cannot expose it to the guest. > So we need to align PCI memory regions to page size (4K) in dom0 kernel > and make sure that each page has only one device's mmio region. > > I found that this problem was discussed a bit in the following thread. > http://lists.xensource.com/archives/html/xen-devel/2007-10/msg01012.html > (linux-2.6.18-xen.hg: changest 296) > Dom0 parameter "pci-mem-align" seems to help aligning mmio regions. > But, at a quick look, mmio regions appear to be aligned not to PAGE_SIZE > but to PAGE_SIZE-1. I also have a concern that re-mapping all the PCI > resources might do harm to some devices unrelated to PCI pass-through. > > Does anyone have an idea about this mmio re-mapping issue ? > (or is anyone already working on this ?) > > Regards, > ------------------- > Yosuke Iwamatsu > NEC Corporation > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel