Re: [Xen-ia64-devel] Notes about driver domains

[Tristan Gingold <Tristan.Gingold@xxxxxxxx>]

Le Mercredi 26 Juillet 2006 03:56, Isaku Yamahata a écrit :
> Hi Tristan.
>
> You already noticed the followings though.
[...]
> > * Currently any domain can do ioremap.  Access checks have to be done.
>
> When I worked on dom0 vp model, I wanted to keep the modification of
> linux ioremap() as small as possible.
> So I made the requirement that pseudo physical address == machine address
> on I/O area.
> assign_domain_mmio_page(), assign_domain_mach_page() realize it.
> It is acceptable and appropriate for dom0.
> But I don't know about driver domains.
>
> - require p=m on I/O area like dom0.
This is the easy solution.  But difficulties may arise if we want to use low 
mmio with a > 4GB domain size!

> - don't require p=m on I/O area and paravirtualize Linux
>   ioremap(),iounmap() more.
I suppose this is the long term solution.

> - other

[...]
> > * memory mapped IO pages should belongs to dom_io pseudo-domain.  At
> > least work is required here to avoid crash when a domain is destroyed.
>
> With CONFIG_VIRTUAL_FRAME_TABLE enabled (this is default),
> struct page_info correspanding to I/O area might not be allocated.
> It is the reason why assign_domain_mmio_page() and
> assign_domain_mmio_page() doesn't increase reference count.
Ok.
I thought there was a problem with that but apparently it is somewhere else.

> These are just ideas when I modified those functions.
> - allocate struct page_info dynamically and make dom_io owns them
>   when they become necessary.
> - go without struct page_info. introduce new pte flag to indicate
>   that it is I/O page and there is no corresponding struct page_info.
>   Probably this requires adding check whether this pte is for I/O
>   before converting pte to struct page_info
I'd tend to prefer this solution.

> - other
>
> > At this time I was able to see an ethernet card in a domU.
>
> Very nice!
Yes but it doesn't work well :-(

Tristan.

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