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

[Jan Kiszka]

On 05.02.26 06:42, Michael Kelley wrote:
> 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!
> 

Indeed:

Powershell> Set-VMComPort -VMName "Debian 13" 1 \\.\pipe\comport

<Start VM>

Powershell> putty -serial \\.\pipe\comport

Well hidden...

Jan

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