Re: [Xen-devel] [PATCH 00/11] Alternate p2m: support multiple copies of host p2m

[Ed White <edmund.h.white@xxxxxxxxx>]

>>
>> The second thing is how similar some of this is to nested p2m code,
>> making me wonder whether it could share more code with that.  It's not
>> as much duplication as I had feared, but e.g. altp2m_write_p2m_entry()
>> is _identical_ to nestedp2m_write_p2m_entry(), (making the
>> copyright claim at the top of the file quite dubious, BTW).
>>
> 
> I did initially use nestedp2m_write_p2m_entry directly, but I knew
> that wouldn't be acceptable! On this specific point, I would be more
> inclined to refactor the normal write entry routine so you can call
> it everywhere, since both the nested and alternate ones are simply
> a copy of a part of the normal one.
> 

I started to look into this again. What I described as the normal write
routine is the one for HAP, and that is actually a domain-level routine
(akin to the paging mode-specific ones), and takes a domain as its first
parameter. The nestedp2m routine is a p2m-level routine that takes a p2m
as its first parameter, and that's what I had copied.

However, looking at the code, the p2m-level write routine is only ever
called from the domain-level one, but the HAP routine doesn't make such
calls, and nestedp2m and altp2m are only available in HAP mode.

Therefore, I have dropped the altp2m write routine with no ill effects.
I don't think the nestedp2m one can ever be called.

Ed


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