Re: [Xen-devel] [PATCH v2 1/3] x86: remove PVHv1 code

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 01/03/17 14:18, Ian Jackson wrote:
> Roger Pau Monne writes ("Re: [PATCH v2 1/3] x86: remove PVHv1 code"):
>> On Wed, Mar 01, 2017 at 01:53:29PM +0000, Ian Jackson wrote:
>>> Well, PVHv2 is in the process of becoming properly supported, so now
>>> is the time to decide the "official" way.
>>
>> I prefer builder="hvm" device_model_version="none" because I think
>> it's clearer from a user PoV that a HVM guest it being
>> created.
> 
> Err, but a PVH guest is not an HVM guest in the sense that the user
> will expect.  Whenever I explain to anyone the difference between PV
> and HVM, the explanation is that "HVM provides a complete emulated PC"
> and "PV needs a guest operating systemn modified to work under Xen".
> By both these measures, a PVH guest is more like PV than HVM.
> 
> The use of the CPU extensions which originally only enabled support
> for HVM is a detail which most people will not be so interested in.
> The details of API, ABI and so on are not of interest to the writer of
> the xl domain config file.
> 
>> OTOH, using pvh=1 it's more obscure, and it isn't clear
>> which kind of guest you are creating, and which options apply to
>> it. Although all that can be fixed in the man page, I think it's
>> less intuitive.
> 
> The explanation we have been giving to ordinary users is that there
> are going to be three kinds of guest: PV, HVM, and the new PVH.

I was in the middle of writing something very similar to the above two
paragraphs, but instead I'll just say that I agree with Ian. :-)

 -George


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