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] question about machine-to-physic table and phy-to-machin

To: Daniel Stodden <stodden@xxxxxxxxxx>
Subject: Re: [Xen-devel] question about machine-to-physic table and phy-to-machine table
From: tgh <tianguanhua@xxxxxxxxxx>
Date: Mon, 26 Mar 2007 09:39:56 +0800
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Sun, 25 Mar 2007 18:38:48 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <1174650272.3803.29.camel@xxxxxxxxxxxxxxxxxxxxxxx>
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: <45F93B96.76E4.0078.0@xxxxxxxxxx> <460333B8.70307@xxxxxxxxxx> <1174650272.3803.29.camel@xxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Thunderbird (Windows/20060909)
Thank you for your reply

I am confused about the meaning and function of  machine-to-physic address

it *is* confusing, admittedly. in my understanding, one reaseon for
'm2p'/'p2m' being used is that guest operating systems, most prominently
linux, have always been using 'pfn' for 'page frame number' and the like
when referring to 'physical' memory. now you need some kind of
distinction in the paravirtual guest case, because those oses will deal
with both.
in the paravirt case, guestos maintain its own mfn which need m2p and p2m ,is it right? I am confused about how does guestOS maintain its virt-to-physic and physic-to-mach mapping ,in the linux ,there is only v2p mapping, how does guestOS maintain its p2m mapping ,and when a virt address is put into a mmu, does cpu hardware convert virt-addr into machine address or guest's phyiscal address?

I am confused about it

could you help me
Thanks in advance
that host memory becoming a non-contiguous, non-physical one clearly
doesn't justify to substitute the names all across the kernel codebase.
equally, you could not name it virtual or similar in the vmm, because
the term 'virtual' has obviously been allocated elsewhere.

so host memory became 'machine' memory. in a different universe, it
might have rather been the actual 'physical' one. or 'host' memory.
virtual machine memory got a 'p' like in both 'pseudo-physical' and/or
'pfn' and i suppose turned for a significant number of people into
'physical' at some point. which is largely misleading.


Xen-devel mailing list