WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

[Xen-devel] Re: [RFC][PATCH] Basic support for page offline

Hi,

At 14:51 +0000 on 18 Feb (1234968681), Jiang, Yunhong wrote: 
> Can you please share me which existing PET-updating code? I browsed
> the code and didn't find approprate function, especially considering
> we need update all level page tables.

xen/arch/x86/mm.c: mod_l1_entry() mod_l2_entry(), etc.

> Just as you stated before, there may have some corner case need
> considered, grant table etc (some is missed in my previous patch). For
> example, if guest has been granted, but the remote domain has not map
> it (i.e. it is in grant_table->shared, but not been mapped still),
> there should have no reference added, but if we don't hold the grant
> table lock, then the backend may mapped a wrong mfn. Such situation is
> difficult to be solved in tools. BTW, I suspect I may missed more
> reference count, for example, the page may be pinned etc, I will
> consider that in my next patch.

It should be possible to have the tools do all the PTE manipulations
with MMU update hypercalls (I think -- Keir may correct me here). Then 
the final hypercall to surrender the page will fail if the grant tables
are wrong; if it does, put the PTEs back and fall back to a live
migration.  Isn't that what your in-xen code does anyway?

> Also, as to your suggestion in previous mail of "since Xen is now
> doing the hard work of pagetable manipulation, I don't think you even
> need to suspend the guest -- just pausing it should be enough and is
> much easier"

As you already pointed out, I was wrong about that -- you need to
suspend the guest to do the p2m manipulations. 

Cheers,

Tim.

-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel