Re: [Xen-ia64-devel][PATCH] add one page attribute to indicate this page is physical IO page

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

Hi Anthony.

I guess you are working on VT-d support for IA64.
You've sent out those patches independently which seem to
be preparation for VT-d support.

However it is very difficult to guess how you are planning to use those
modifications eventually. So it's very difficult to review those patches.
At this moment I can comment only on patch style which isn't essential.

If you already have working patches, could you please send them
as a series of patches? (Even un-cleaned patches would help to understand.)
If not, could you provide overview of the design or something like 
that which helps me to understand its overview and how VT-d patches
will be implemented.

At this moment the followings come into my mind. (Random thoughts)
- One of the Xen/IA64 features is lockless P2M table unlike x86 case.
  I think it would be very difficult to maintain the VT-d translation table 
  consistent with the p2m and m2p tables without lock.

- What scope are you aiming?
  Now x86 supports VT-d for VMM protection, dom0, PV domU and HVM
  with balloon.
  On the other hand ia64 doesn't support balloon for HVM because
  the p2m for HVM domain is assumed to be read-only.
  How about MSI(-X)?

thanks,

On Sun, Sep 28, 2008 at 12:48:48PM +0800, Xu, Anthony wrote:
> Add _PAGE_DIRECT_IO page attribute to indicate this page is physical IO page
> 
> Signed-off-by; Anthony Xu < anthony.xu@xxxxxxxxx >


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> Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
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-- 
yamahata

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