RE: [EXTERNAL] [PATCH] scsi: storvsc: Fix scheduling while atomic on PREEMPT_RT

[Michael Kelley]

From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> Sent: Monday, February 2, 2026 9:58 PM
> 
> On 03.02.26 00:47, Long Li wrote:
> >> From: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> >>
> >> This resolves the follow splat and lock-up when running with PREEMPT_RT
> >> enabled on Hyper-V:
> >
> > Hi Jan,
> >
> > It's interesting to know the use-case of running a RT kernel over Hyper-V.
> >
> > Can you give an example?
> >
> 
> - functional testing of an RT base image over Hyper-V
> - re-use of a common RT base image, without exploiting RT properties
> 
> > As far as I know, Hyper-V makes no RT guarantees of scheduling VPs for a VM.
> 
> This is well understood and not our goal. We only need the kernel to run
> correctly over Hyper-V with PREEMPT-RT enabled, and that is not the case
> right now.
> 
> Thanks,
> Jan
> 
> PS: Who had to idea to drop a virtual UART from Gen 2 VMs? Early boot
> guest debugging is true fun now...
> 

Hmmm. I often do printk()-based debugging via a virtual UART in a Gen 2
VM. The Linux serial console outputs to that virtual UART and I see the
printk() output in PuTTY on the Windows host. What specifically are you
trying to do?  I'm trying to remember if there's any unique setup required
on a Gen 2 VM vs. a Gen 1 VM, and nothing immediately comes to mind.
Though maybe it's just so baked into my process that I don't remember it!

Michael