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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 16:22:46 +0800
Cc: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, Xen Developers <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Keir Fraser wrote:
On 18/11/08 01:17, "Zhai, Edwin" <edwin.zhai@xxxxxxxxx> wrote:

We are trying to fix a HVM live migration bug, and found "Use main memory for
video memory" in r18383 cause guest hang after restore.

Following changes make all valid pages migrated, including vlapic page
(0xFEE00), and share page(0xFFFFF), so an extra memory population for these 2
pages would override previous mapping then cause guest hang (if using vlapic
acceleration).

What do you think of possible fixing? Skipping these specific pages in
xc_domain_save except video memory, or change the HVM domain creation.

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

Thanks,


 -- Keir



--
best rgds,
edwin


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