Re: [Xen-devel] fixed location of share info page in HVM guests

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 27/08/2012 22:32, "Olaf Hering" <olaf@xxxxxxxxx> wrote:

>>> Recently I tried to move the shared_info page in the pvops kernel during
>>> shutdown, see "xen PVonHVM: move shared_info to MMIO before kexec"
>>> patch. But this change was reverted because it caused reboot failures
>>> because the actual moving of the shared page is fragile.
>> 
>> How was it fragile? Moving it into MMIO should just work?
> 
> The moving itself is not the issue, but the possible access to the page
> during the move. Its not atomic, nor can it easily be atomic.

Why not map it into MMIO in the first place, rather than into the middle of
RAM? Do that early during boot, and early during resume from
save/restore/migrate (i.e., places you presumably already map the
shared_info page, but into the middle of RAM)?

 -- Keir



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