Re: [Xen-users] Plans to require CPU VT flag?

[George Dunlap <dunlapg@xxxxxxxxx>]

On Wed, Dec 20, 2017 at 2:15 PM, Christopher Myers <cmyers@xxxxxxxxxxxx> wrote:
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> On Wed, 2017-12-20 at 09:58 +0000, George Dunlap wrote:
>> On Tue, Dec 19, 2017 at 9:58 PM, Christopher Myers <cmyers@millikin.e
>> du> wrote:
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>> > Out of curiosity, are there any plans to *require* the VT CPU flag
>> > in
>> > Xen at any point in the foreseeable future? The reason I ask is
>> > because
>> > my server at home doesn't support them, so I want to beware of any
>> > version that would break my current setup.
>> >
>> > Right now I've got four PV VMs running on my Xen box (4.8.3 on
>> > Debian
>> > Stretch,) and am perfectly content with its performance :)
>>
>> At the moment it's not possible to boot Xen without a PV domain 0 (on
>> x86). :-)
>>
>> We are working on allowing PVH dom0 (which requires HVM* support),
>> but
>> that won't be ready until 4.11 or 4.12; even if we were planning on
>> phasing it out, it wouldn't be possible for several years.
>>
>> But, there is no intention at this point of phasing out PV.  As you
>> say, there continues to be lots of x86 hardware (even new hardware)
>> that doesn't have HVM support; for those platforms Xen will be
>> basically the only option.
>
> Awesome, thanks very much :)
>
> It really is amazing how much you can do with Xen. My setup is an Aaeon
> EMB CV1 A11 industrial motherboard (Atom D2550 processor) with 4GB of
> memory. On that I'm able to run four Debian Stretch PV DomU's without
> issue --
>  - asterisk VOIP server
>  - nginx reverse proxy
>  - dedicated bind9 VM
>  - "the everything" vm, running the usual LAMP stack, minecraft server,
> rsyslog aggregator, nextcloud, secondary bind9 instance, email server,
> mantisbt, and about a half dozen other applications.
>
> When you think about the fact that this is, in reality, running off of
> two (not overly powerful) CPU cores, and performs very smoothly on top
> of all that...

That's good feedback, thanks.  Intel Atom always comes up in
discussions about why we need to keep PV, but I think until now it was
always theoretical ("someone may want to do X").  Having at least one
concrete user who has actually used X makes it a lot easier to justify
supporting X. :-)

 -George

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