Re: Kernel panic on 'floppy' module load, Xen HVM, since 4.19.143

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Tue, Sep 29, 2020 at 04:05:21PM +0200, Jürgen Groß wrote:
> On 29.09.20 14:41, Marek Marczykowski-Górecki wrote:
> > On Tue, Sep 29, 2020 at 03:27:43PM +0300, Denis Efremov wrote:
> > > Hi,
> > > 
> > > On 9/28/20 12:36 PM, Marek Marczykowski-Górecki wrote:
> > > > On Mon, Sep 28, 2020 at 07:02:19AM +0200, Jürgen Groß wrote:
> > > > > On 27.09.20 13:14, Marek Marczykowski-Górecki wrote:
> > > > > > Hi all,
> > > > > > 
> > > > > > I get kernel panic on 'floppy' module load. If I blacklist the module,
> > > > > > then everything works.
> > > > > > The issue happens in Xen HVM, other virtualization modes (PV, PVH) works
> > > > > > fine. PV dom0 works too. I haven't tried bare metal, but I assume it
> > > > > > works fine too.
> > > > > 
> > > > > Could you please try bare metal?
> > > > 
> > > > I don't have any hw with floppy controller at hand...
> > > > Booting on what I have, it works, loading floppy just says -ENODEV.
> > > 
> > > I saw that the issue was bisected [1] to commit
> > > c330fb1ddc0a ("XEN uses irqdesc::irq_data_common::handler_data to store a
> > > per interrupt XEN data pointer which contains XEN specific information.")
> > > 
> > > I have hardware, but I've never worked with Xen. It will take me some time
> > > to set it up and reproduce the problem. I think I will do it in a week.
> > 
> > Can you try to boot 4.19.143 (or any other including that commit)
> > directly on the hardware and make sure floppy module is loaded? We do
> > know it's broken in Xen HVM, it would be interested to see if it works
> > without Xen. Even better if you could use the same kernel config:
> > https://gist.github.com/marmarek/1e6a359c9a99af3ed8fc16af0f36d8a6
> 
> I think it is not directly related to floppy, but a more general problem
> for HVM guests.
> 
> I'm suspecting an issue with legacy IRQs. Could you please try the
> attached patch?

Yes, this fixes the issue.

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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