Re: [Xen-devel] [PATCH for-4.11] x86/dom0: add extra RAM regions as RESERVED for PVH memory map

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, May 03, 2018 at 08:55:14PM +1000, Alexey G wrote:
> On Thu, 3 May 2018 10:56:40 +0100
> Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
> 
> >When running as PVH Dom0 the native memory map is used in order to
> >craft a tailored memory map for Dom0 taking into account it's memory
> >limit.
> >
> >Dom0 memory is always going to be smaller than the total amount
> >of memory present on the host, so in order to prevent Dom0 from
> >relocating PCI BARs over RAM regions mark all the RAM regions not
> >available to Dom0 as RESERVED in the memory map.
> >---
> >NB: I haven't seen any system where Dom0 would relocate the BARs over
> >RAM regions, but AFAICT given the current memory map provided to Dom0
> >this is a possibility that should be avoided.
> 
> Guest OSes typically use information from ACPI to learn where PCI
> BARs can (or cannot) be relocated.

I think it's better to be safe than sorry, so IMO the host RAM regions
should be added to the memory map as RESERVED.

Roger.

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