RE: [Xen-devel] HVM Save/Restore status.

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: Keir Fraser [mailto:keir@xxxxxxxxxxxxx] 
> Sent: 25 April 2007 17:51
> To: Petersson, Mats; Tim Deegan
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Woller, Thomas
> Subject: Re: [Xen-devel] HVM Save/Restore status.
> 
> 
> 
> 
> On 25/4/07 17:15, "Petersson, Mats" <Mats.Petersson@xxxxxxx> wrote:
> 
> > So, a few printf later: The first time (which succeds) and 
> the second
> > time (which fails) is exactly the same frame numbers (1fff, 
> 1ffe, 1ffd).
> > It fails on the FIRST (I split the "if( ... [0] || ... [1] 
> || ... [2] )"
> > into separate lines, and print the failure on each with a "[n]" to
> > indicate which one failed, and it got [0] in the printout.
> 
> Mats,
> 
> Can you try adding 1 to p2m_size after the line:
> p2m_size = xc_memory_op(xc_handle, XENMEM_maximum_gpfn, &dom);
> In xc_domain_save.c, please. I think we have an out-by-one 
> error that you
> are triggering because your mini-domain does not drive the 
> cirrus_vga lfb
> and hence does not have any 'video ram' mapped in the RAM 
> hole. You might
> also want to print p2m_size in xc_domain_save and confirm 
> this hypothesis
> that way too.

Ok, here goes:
First save: p2m_size = 0xfffff (succeeds)
Second sace: p2m_size = 0x1fff (fails)

I'm a little bit surprized about the first number, as it's about 4GB(?)
(my domain is officially only 32MB, and uses a whole lot less actual
memory), but I guess the second number should be 0x2000 if it's the
actual size rather than the highest number of pfn available in the
guest. Does that make sense to you?

[Aside from my printout, there's also a printout already in the xend.log
from xc_domain_restore start: p2m_size = xxxxx which displays the same
data as I've reported above, both before my change and after it, so I do
believe my printout isn't completely bogus]. 

--
Mats
> 
> This would also bite us for other guests with more than 4GB 
> (we'd lose a
> page per save/restore, I think). So this is a nice one to fix 
> before 3.0.5
> if I'm right!
> 
>  -- Keir
> 
> 
> 
> 



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