Re: Possible bug? DOM-U network stopped working after fatal error reported in DOM0

["G.R." <firemeteor@xxxxxxxxxxxxxxxxxxxxx>]

On Fri, Dec 31, 2021 at 2:52 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
>
> On Thu, Dec 30, 2021 at 11:12:57PM +0800, G.R. wrote:
> > On Thu, Dec 30, 2021 at 3:07 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> 
> > wrote:
> > >
> > > On Wed, Dec 29, 2021 at 11:27:50AM +0100, Roger Pau Monné wrote:
> > > > On Wed, Dec 29, 2021 at 05:13:00PM +0800, G.R. wrote:
> > > > > >
> > > > > > I think this is hitting a KASSERT, could you paste the text printed 
> > > > > > as
> > > > > > part of the panic (not just he backtrace)?
> > > > > >
> > > > > > Sorry this is taking a bit of time to solve.
> > > > > >
> > > > > > Thanks!
> > > > > >
> > > > > Sorry that I didn't make it clear in the first place.
> > > > > It is the same cross boundary assertion.
> > > >
> > > > I see. After looking at the code it seems like sglist will coalesce
> > > > contiguous physical ranges without taking page boundaries into
> > > > account, which is not suitable for our purpose here. I guess I will
> > > > either have to modify sglist, or switch to using bus_dma. The main
> > > > problem with using bus_dma is that it will require bigger changes to
> > > > netfront I think.
> > >
> > > I have a crappy patch to use bus_dma. It's not yet ready for upstream
> > > but you might want to give it a try to see if it solves the cross page
> > > boundary issues.
> > >
> > I think this version is better.
>
> Thanks for all the testing.
>
> > It fixed the mbuf cross boundary issue and allowed me to boot from one
> > disk image successfully.
>
> It's good to know it seems to handle splitting mbufs fragments at page
> boundaries correctly.
>
> > But seems like this patch is not stable enough yet and has its own
> > issue -- memory is not properly released?
>
> I know. I've been working on improving it this morning and I'm
> attaching an updated version below.
>
Good news.
With this  new patch, the NAS domU can serve iSCSI disk without OOM
panic, at least for a little while.
I'm going to keep it up and running for a while to see if it's stable over time.

BTW, an irrelevant question:
What's the current status of HVM domU on top of storage driver domain?
About 7 years ago, one user on the list was able to get this setup up
and running with your help (patch).[1]
When I attempted to reproduce a similar setup two years later, I
discovered that the patch was not submitted.
And even with that patch the setup cannot be reproduced successfully.
We spent some time debugging on the problem together[2], but didn't
bottom out the root cause at that time.
In case it's still broken and you still have the interest and time, I
can launch a separate thread on this topic and provide required
testing environment.

[1] https://lists.xenproject.org/archives/html/xen-users/2014-08/msg00003.html
[2] https://xen-users.narkive.com/9ihP0QG4/hvm-domu-on-storage-driver-domain

Thanks,
G.R.

> Thanks, Roger.