Re: [Xen-devel] [RFC Patch] Support for making an E820 PCI hole in toolstack (xl + xm)

[Keir Fraser <keir@xxxxxxx>]

On 16/11/2010 10:02, "Ian Campbell" <Ian.Campbell@xxxxxxxxxxxxx> wrote:

>> The right answer is probably to refuse save/restore/migrate when devices are
>> passed through.
> 
> Absolutely. 
> 
> However we are talking about setting up a 1-1 mapping in the P2M region
> corresponding to the PCI hole at guest boot and preserving that until
> such a time as a device is plugged in, which may be after a migration.
> 
> I don't think it matters that no device is passed through at the time of
> the migration, in this configuration we still need arrange for the
> relevant P2M entries to be correct after the migration (or at least
> before the device gets plugged in, perhaps we can leave holes and only
> establish the 1-1 p2m on demand in pcifront?).

Leave the hole empty and populate on demand when devices are passed through
would seem sensible.

 -- Keir

> So long as this configuration doesn't cause the save/restore code to go
> mad it's something we can likely fixup in the guest on restore. My worry
> is that the save/restore code will just barf before we get that
> opportunity...




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