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

[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.


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



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