Re: [Xen-devel] [PATCH 07/11] x86/altp2m: introduce p2m_ram_rw_ve type.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.01.15 at 21:38, <edmund.h.white@xxxxxxxxx> wrote:
> On 01/15/2015 09:03 AM, Tim Deegan wrote:
>> At 13:26 -0800 on 09 Jan (1420806397), Ed White wrote:
>>> This is treated exactly like p2m_ram_rw, except that suppress_ve is not
>>> set in the EPTE.
>> 
>> I don't think this is going to work -- you probably want to support
>> p2m_ram_ro at least, and maybe other types, but duplicating each of
>> them as a 'type foo with #VE' doesn't seem right.
>> 
>> Since the default is to set the ignore-#ve flag everywhere, how about
>> having an operation to enable #ve for a frame that just clears that
>> bit, and then having all other updates to altp2m entries preserve it?
> 
> I hear you, but #VE is only even relevant for the in-domain agent
> model, and as the only current user of that model we not only don't
> want #VE to work on other page types, we specifically want it to be
> prohibited.
> 
> Can we do it this way, and then change it later if required?

Without you explaining to us the full details of the in-domain
agent model, I'm afraid this is going to remain dubious and the
question hard to answer. In particular, if you indeed want to
prohibit that behavior on _all_ other p2m types, how would
subsequently changing the implementation then be compatible
(if it can't be done this way right from the beginning)?

Jan


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