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Re: [Xen-devel] several Qs about domain live migration

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] several Qs about domain live migration
From: "Zhai, Edwin" <edwin.zhai@xxxxxxxxx>
Date: Tue, 18 Nov 2008 17:35:06 +0800
Cc: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>, "Zhai, Edwin" <edwin.zhai@xxxxxxxxx>
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Keir,
As my test, video mem and vlapic page are okay, but share page is
still treated as ram.

After going through the source code, I think this should be "no harm".
Although xc_domain_restore populate a new share page first, PV driver
in HVM guest will remap share page when resume, thus destroying
previous mapping and releasing previous page.

So we want to use this simple patch, or mark the share page "not ram"?


Keir Fraser wrote:
 On 18/11/08 08:22, "Zhai, Edwin" <edwin.zhai@xxxxxxxxx> wrote:

>> Try changing gmfn_to_mfn(FOREIGNDOM, l1e_get_pfn(nl1e)) in
mod_l1_entry()
>> to:
>>   mfn = gfn_to_mfn(FOREIGNDOM, l1e_get_pfn(nl1e), &p2mt);
>>   if ( !p2m_is_ram(p2mt) || (mfn == INVALID_MFN) )
>>     ....
>>
>> This will prevent foreign mappings of 'mmio' pages. Pretty sensible
and will
>> fix this problem.
>> > It's great!
> Does p2m_is_ram return 1 for video memory?

Yes, since it is just ordinary guest memory. That was the point of
Samuel's
 patch.

 -- Keir

> I'll make a small patch and test it.



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--
best rgds,
edwin


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