Status of 64 bit DomU PVs?

[Cherry G. Mathew]

Hi Jonni,

Date: Sat, 05 Apr 2014 00:39:24 +0300
> From: Jonni Nakari <jonni at egarden.fi>
> To: freebsd-xen at freebsd.org
> Subject: Status of 64 bit DomU PVs?
> Message-ID: <533F268C.8040909 at egarden.fi>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hello,
> what is the current status of 64 bit paravirtualized FreeBSD? The wiki
> page Xen wiki page [1] states that only i386 kernels can be run in fully
> paravirtualized mode. The wiki page hasn't been updated in a while. Has
> anything changed since the last update?
>
> I would like to run FreeBSD as a DomU on a AMD 64 bit machine that does
> not have hardware accelerated virtualization. That propably means that
> it's not feasible to run a HVM based DomU on the machine? I would also
> like the DomU to be 64 bit to provide more than 4 gigabytes of RAM to
> the ZFS serving FreeBSD.
>
>
I've been working on this for quite some time now (perhaps too long), and
the bad news is that, no, it's not ready for use - the code on the branch
does bring us up to single user mode, but I'm reworking the pmap module
with the wisdom of hindsight. The good news is that it should be ready for
testing "soon" (May, 2014).

With PV on 64bit, you should be able to have a 64bit address space with
support for 47bit RAM (in theory).



> Or maybe I have misunderstood something. Is it possible to provide more
> than 4 GB RAM for a 32 bit DomU so that it can use all of it for ZFS
> caching?
>
>
On 64bit PV, the DomU is 64bit (although there used to be support for 32bit
PV on 64bit hypervisor until the 3.x hypervisors, iirc). So yes, you should
in *theory*, be able to have more than 4GB ram for your 64bit DomU.

You're welcome to try the amd64_xen_pv svn branch, although it's very very
early days, and I doubt it would be useful in any way for you other than to
track progress or help with dev.

Many Thanks,
-- 
~Cherry
(cherry at FreeBSD.org)