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Re: [Xen-users] opensolaris/illumos on PVHVM under 4.x.y?

On 14/03/13 23:30, Eric Shelton wrote:
> [sorry for the dupe, the previous message was sent out prematurely...]
> I was hoping to implement a storage domain using blkback to serve up
> ZFS zvols, to see how it works out.  Is anyone successfully running
> opensolaris with PV drivers under HVM on Xen 4.x.y? 

PVHVM is not just getting a PV guest booting under a HVM container.
There are some differences in the way PV or PVHVM perform certain
operations, so it's not just a matter of putting the PV drivers, for
example the event channel callback used in PVHVM is different from the
one used in PV, and also the way to map grant frames. AFAIK Illumos
doesn't have PVHVM support, so it will take some work to get it running.

If you are interested in running ZFS backends why don't you take a look
at FreeBSD PVHVM? It comes with ZFS, frontends and backends, and runs in
PVHVM mode without problems.

> I am running on an
> AMD IOMMU capable computer.  The closest I have gotten is:
> (1) coaxing openindiana into booting up as a PV guest (not a smooth
> out-of-the-box type of install)
> (2) with acpi=0, an HVM boot will go pretty far, but there is a bug
> present in 151a7, in which the hvm_sd and sd modules fail to load due
> to being improperly built and take down the boot.  A patch for this
> issue was entered into the illumos-gate repository, but does not
> appear to have been used for any current distribution.
> (3) with acpi=0 and use of the kernel bugger (::bp get_hwenv, :c,
> platform_type/W 0, ::delete 1, :c), I can get openindiana to boot up a
> plain PC kernel.  I think I recall network and/or PV driver issues
> being a problem.
> (4) I tried out some illumos-gate kernel build/installs, but the
> typical response from a new build is some kind of a hang or lockup
> that is unresponsive to the F1-A kernel debugger.  However, I am
> definitely stumbling my way through this, so I may not have run the
> kernel build or install correctly.
> OmniOS dies pretty quickly, whether under PV or HVM.
> I am beginning to get the impression that there was an active PV and
> functional driver under Xen 3, but that the illumos PV drivers did not
> keep up with various changes required to interoperate with Xen 4 (or
> at least the more recent Xen releases).

There was someone from the Illumos community working on getting back the
full Xen PV support to Illumos, both as Dom0/DomU, but I think the work
is stalled right now.

> Even if I were to consider
> KVM, although virtio-blk looks like it may be OK, a proposed
> virtio-net driver has not been accepted into illumos-gate, and is of
> unknown quality (it appears to be a slightly tweaked version of a
> prototype driver that was admitted to be incomplete by its original
> author).  There appear to be suggestions that PVHVM has been
> maintained and works in Solaris 11, but I would much more strongly
> prefer using one of the illumos-based distributions.
> If there is anyone running opensolaris outside of PV (in other words,
> under HVM) under Xen 4.x.y, what is your Xen guest config, and which
> distribution are you using?
> Also, in sorting out how I might boot a plain non-HVM kernel (see use
> of the kernel debugger under (3) above), it looks like the
> "xen_platform_pci" parameter in xl.cfg-type files does nothing as the
> code presently stands - defeinitely when using qemu-upstream, and I
> think also under qemu-traditional.  The xenpci device continues to
> show up on the virtual PCI bus under "xen_platform_pci=0".  However,
> even if the xenpci device was toggled on/off, it turns out illumos
> would still boot an HVM kernel, as it uses the availability of the
> 0x40000000 cpuid info to identify when it is running under Xen (hence
> the debugger procedure set out in (3) above).  If xen_platform_pci is
> set to 0, is this Xen cpuid functionality supposed to be diabled?
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