Re: [Xen-devel] [PATCH RFC] libxl: set 1GB MMIO hole for PVH

[Juergen Gross <jgross@xxxxxxxx>]

On 09/05/18 18:07, Roger Pau Monne wrote:
> This prevents page-shattering, by being able to populate the RAM
> regions below 4GB using 1GB pages, provided the guest memory size is
> set to a multiple of a GB.
> 
> Note that there are some special and ACPI pages in the MMIO hole that
> will be populated using smaller order pages, but those shouldn't be
> accessed as often as RAM regions.

Would it be possible somehow to put a potential firmware into that
1GB region, too, if it needs any memory in high memory? Seabios e.g.
is taking the last RAM page of the guest for its hypercall page, which
will again shatter GB mappings.


Juergen

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