Re: [Xen-devel] [PATCH] libxc: fix claim mode when creating HVM guest

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Mon, Jan 27, 2014 at 07:09:45PM +0000, George Dunlap wrote:
> On 01/27/2014 05:53 PM, Wei Liu wrote:
> >The original code is wrong because:
> >* claim mode wants to know the total number of pages needed while
> >   original code provides the additional number of pages needed.
> >* if pod is enabled memory will already be allocated by the time we try
> >   to claim memory.
> >
> >So the fix would be:
> >* move claim mode before actual memory allocation.
> >* pass the right number of pages to hypervisor.
> >
> >The "right number of pages" should be number of pages of target memory
> >minus VGA_HOLE_SIZE, regardless of whether PoD is enabled.
> >
> >This fixes bug #32.
> >
> >Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
> >Cc: Konrad Wilk <konrad.wilk@xxxxxxxxxx>
> >Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> >Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
> >Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> 
> Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

and tomorrow I should be able to test it out as well.
> 
> >---
> >WRT 4.4 release: this patch should be accpeted, otherwise PoD + claim
> >mode is complete broken. If this patch is deemed too complicated, we
> >should flip the switch to disable claim mode by default for 4.4.
> 
> I think a more reasonable mitigation strategy would simply be to
> ignore claim mode when constructing a domain that uses PoD.
> 
> I'm inclined to take this one.  Since claim mode is on by default,
> the currently-working path should get exercised well before the
> release to shake out any bugs.  The other path doesn't work at all
> currently (AFAICT) unless you disable claim mode -- which is still
> available as a work-around, even if there is a bug in this patch.
> 
> I'll wait a day or two for others to speak up before giving it a
> formal ack, just in case.
> 
>  -George

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