From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Zhai, Edwin" <edwin.zhai@intel.com>
Subject: Re: memsize for HVM save/restore
Date: Mon, 26 Mar 2007 11:13:18 +0800
Message-ID: <20070326031318.GZ21485@edwin-srv.sh.intel.com>
References: <20070324113720.GX21485@edwin-srv.sh.intel.com>
	<C22AE3C4.C2D9%Keir.Fraser@cl.cam.ac.uk>
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To: Keir Fraser <Keir.Fraser@cl.cam.ac.uk>
Cc: xen-devel@lists.xensource.com, Ewan Mellor <ewan@xensource.com>, "Zhai,
	Edwin" <edwin.zhai@intel.com>
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On Sat, Mar 24, 2007 at 02:18:44PM +0000, Keir Fraser wrote:
> On 24/3/07 11:37, "Zhai, Edwin" <edwin.zhai@intel.com> wrote:
> 
> > But then qemu broke, because it also require the memsize to locate the share
> > page. We can't use the previous method, as it requires a lot of changes in
> > qemu.
> 
> Doesn't your new 'general layout' patch put the PFNs of xenstore, ioreq,
> buffered_ioreq in the saved image, and restore in xc_hvm_restore? Qemu-dm

yes,

> should obtain the addresses via HVMOP_get_param.
> 
> You do not need the memsize parameter.

I don't think so.
Besides locating PFNs, memsize is also used in QEMU for other purpose, such as 
bitmap allocation, dev init and map_foreign*. So memsize is a must for qemu 
init.

See following code in xc_hvm_build:
if ( v_end > HVM_BELOW_4G_RAM_END )
    shared_page_nr = (HVM_BELOW_4G_RAM_END >> PAGE_SHIFT) - 1;
else
    shared_page_nr = (v_end >> PAGE_SHIFT) - 1;

So it's impossible to get memsize by saved PFNs when restore a big memory guest.

 
> 
>  -- Keir
> 

-- 
best rgds,
edwin