This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] Essay on an important Xen decision (long)

To: Anthony Liguori <aliguori@xxxxxxxxxx>, "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
Subject: Re: [Xen-devel] Essay on an important Xen decision (long)
From: Tristan Gingold <Tristan.Gingold@xxxxxxxx>
Date: Wed, 11 Jan 2006 11:46:47 +0100
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Wed, 11 Jan 2006 09:49:50 +0000
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <43C41133.3050606@xxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <516F50407E01324991DD6D07B0531AD59030F8@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <43C41133.3050606@xxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: KMail/1.5
Le Mardi 10 Janvier 2006 20:55, Anthony Liguori a écrit :
> Hi Dan,
> Thanks for the thorough explaination of physical memory virtualization.
> It's a topic that there isn't a lot of good reference on.
> You seem to conclude that the only possible solutions are making the
> dom0 either P==M or P2M.  Is it not possible to make dom0 VP?
> If the only issue for making dom0 VP is DMA, wouldn't it be easier to
> modify the Linux DMA subsystem[1] to make a special hypercall to
> essentially pin a VP to a particular MFN that could be used for the
> DMA?  One could imagine the hypervisor reversing low memory specifically
> for DMA such that bounce buffers could be avoided too.
> VP makes a lot of interesting memory optimizations considerably easier
> (memory compacting, swapping, etc.).
> [1] Realizing that I know very little about the Linux DMA subsystem so I
> don't know if this is outside the realm of possibilities.

a few years ago (it was with linux 2.2), I wrote device drivers for rather 
complex hardware.  DMA subsystem didn't really exist.  The main reason is an 
hardware reason: DMA chip do not exist anymore because nowaday (almost since 
PCI) every driver chip do DMA by itself.


Xen-devel mailing list