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

[Keir Fraser <keir@xxxxxxx>]

On 15/11/2010 18:15, "Konrad Rzeszutek Wilk" <konrad.wilk@xxxxxxxxxx> wrote:

>> Well it is all quite Xen specific, so I'm surprised.
> 
> Oh, there was another reason that I so obvious that I completly forgot. DomU
> has no idea where the host PCI hole starts. In most cases it is at 3GB (or
> even
> further up - 3.5GB), but a quick look for 'Allocating PCI resources starting
> at' 
> at Google shows that there are some that start at 1.2G.

Hm, true. We could give you access to XENMEM_machine_memory_map? It's not
really got any big secrets or privileged things in it. :-)

Or, is there much disadvantage, to having a static really big PCI hole? Say
starting at 1GB? The advantage of this would be the ability to hotplug PCI
devices to a domU even across save/restore/migrate -- this may not work so
well if you commit yourself to the hole size of the original host, and the
restore/migrate target host has a bigger hole!

 -- Keir



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