Re: [Xen-devel] [PATCH] xen/x86: Force removal of memory range when not covered by MTRRs

[Keir Fraser <keir@xxxxxxx>]

On 15/02/2013 13:47, "Konrad Rzeszutek Wilk" <konrad.wilk@xxxxxxxxxx> wrote:

>> What Dom0 does to its representation of the E820 map is of no
>> concern to the hypervisor. So are we in agreement then that the
>> hypervisor code is fine without any changes?
> 
> I am not clear on what the right fix is. Dom0 could interpret E820_UNUSABLE
> as memory to be considered as E820_RESERVED - but then I am wondering what
> to do with hotplug memory. As in, does the BIOS mark memory that can be
> hotplugged
> as E820_RESERVED or E820_UNUSABLE? So if we mark the memory as E820_RESERVED
> and the hotplug memory code expects that - will we confuse it as there are now
> new ranges of it?
> 
> Perhaps dom0 should just eviscerate that range altogether. But then it will
> be considered as MMIO region and that will lead to trouble with i915 at least.

I don't think E820_RESERVED is specifically for hotplug use only, and we
could use it here in place of E820_UNUSABLE. That may be more correct, since
E820_UNUSABLE is specifically intended for RAM in which errors have been
detected.

 -- Keir



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