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Re: [Xen-devel] [PATCH v3] docs: add PVH specification

On Thu, 18 Sep 2014 19:19:24 +0200
Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:

> Introduce a document that describes the interfaces used on PVH. This
> document has been designed from a guest OS point of view (i.e.: what
> a guest needs to do in order to support PVH).
> +
> +*TODO*: we need to figure out what to do with MMIO regions, right
> now Xen +sets all the holes in the native e820 to MMIO regions for
> Dom0 up to 4GB. We +need to decide what to do with MMIO regions above
> 4GB on Dom0, and what to do +for PVH DomUs with pci-passthrough.

My previous comment in earlier version on this:

"We map all non-ram regions for dom0 1:1 till the highest non-ram e820
entry. If there is anything that is beyond the last e820 entry,
it will remain unmapped."

The 4GB comment in the function pvh_map_all_iomem() refers to when
a BIOS may not report io space above ram when ram is less than 4GB.

> +In the case of a guest started with memory != maxmem, the e820
> memory map +returned by Xen will contain the memory up to maxmem. The
> guest has to be very +careful to only use the lower memory pages up
> to the value contained in +`start_info->nr_pages` because any memory
> page above that value will not be +populated.
> +
> +## Physical devices ##
> +
> +When running as Dom0 the guest OS has the ability to interact with
> the physical +devices present in the system. A note should be made
> that PVH guests require +a working IOMMU in order to interact with
> physical devices. +
> +The first step in order to manipulate the devices is to make Xen
> aware of +them. Due to the fact that all the hardware description on
> x86 comes from +ACPI, Dom0 is responsible of parsing the ACPI tables
> and notify Xen about the +devices it finds. This is done with the


Dom0 is responsible for parsing the ACPI tables and notifying Xen

With that, thanks Roger, and :

Acked-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>


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