Re: [Xen-devel] [PATCH][v2] Hybrid extension support in Xen

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 02/02/2010 11:22, "Ian Campbell" <Ian.Campbell@xxxxxxxxxxxxx> wrote:

> On Tue, 2010-02-02 at 08:16 +0000, Sheng Yang wrote:
>> 
>> +/* Reserve 128KB for grant table */
>> +#define GNTTAB_MEMBASE     0xfbfe0000
>> +#define GNTTAB_MEMSIZE     0x20000
> 
> Why is this necessary? Isn't the grant table contained within one of the
> BARS on the virtual PCI device? What needs grant tables for prior to the
> kernel finding the PCI device which necessitates hardcoding these
> addresses in both guest and hypervisor?

I didn't even find where these get used, except to reserve an area in e820,
and it wasn't clear why that reservation is necessary.

 -- Keir



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