Re: [Xen-devel] How to initialize the grant table in a HVM guest OS and its bios

[Bei Guan <gbtju85@xxxxxxxxx>]

2012/8/8 Ian Campbell <Ian.Campbell@xxxxxxxxxx>

On Wed, 2012-08-08 at 16:10 +0100, Bei Guan wrote:
> Hi,
>
>
> In Mini-OS, the initialization of the grant table maps the grant table
> entries into an area called demand_map_area. The code is in the file
> mini-os/gnttab.c and it's like this
> gnttab_table = map_frames(frames, NR_GRANT_FRAMES);
>
>
> It seems that getting the demand_map_area needs the infomation from
> the start_info page in Mini-OS (refer to the method allocate_ondemand
> int mini-os/arch/x86/mm.c). However, there is no start_info page in a
> HVM guest OS (maybe it's also true for its virtual bios, such as
> seabios and uefi bios). So, how to map the grant table entries in a
> HVM guest OS and its bios?

The PCI Platform device provides a BAR region which is specifically set
aside for the guest OS to use as a hole for grant tab mappings. Or if
you control the phyiscal address space you can just allocate somewhere
to do the mapping.

Hi Ian,

Thank you very much for your help.

Is there any example code of initialization of grant table in HVM that I can refer to?

Thanks,

Bei Guan

 

>
>
> Any suggestions is appreciated.
>
>
>
>
> Best Regards,
> Bei Guan
>

-- 
Best Regards,

Bei Guan

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