From: Naman Jain <namjain@linux.microsoft.com>
To: Wei Liu <wei.liu@kernel.org>, Jan Kiszka <jan.kiszka@siemens.com>
Cc: Magnus Kulke <magnuskulke@linux.microsoft.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Dexuan Cui <decui@microsoft.com>, Long Li <longli@microsoft.com>,
Thomas Gleixner <tglx@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, linux-hyperv@vger.kernel.org,
linux-kernel@vger.kernel.org,
Florian Bezdeka <florian.bezdeka@siemens.com>,
RT <linux-rt-users@vger.kernel.org>,
Mitchell Levy <levymitchell0@gmail.com>,
skinsburskii@linux.microsoft.com, mrathor@linux.microsoft.com,
anirudh@anirudhrb.com, schakrabarti@linux.microsoft.com,
ssengar@linux.microsoft.com
Subject: Re: [PATCH] x86: mshyperv: Use kthread for vmbus interrupts on PREEMPT_RT
Date: Fri, 6 Feb 2026 13:02:52 +0530 [thread overview]
Message-ID: <76e8cfd8-f48d-4129-bb9d-ca58c24b29a4@linux.microsoft.com> (raw)
In-Reply-To: <20260204073629.GP79272@liuwe-devbox-debian-v2.local>
On 2/4/2026 1:06 PM, Wei Liu wrote:
> On Wed, Feb 04, 2026 at 08:32:04AM +0100, Jan Kiszka wrote:
>> On 04.02.26 08:29, Wei Liu wrote:
>>> On Wed, Feb 04, 2026 at 08:26:48AM +0100, Jan Kiszka wrote:
>>>> On 04.02.26 08:19, Jan Kiszka wrote:
>>>>> On 04.02.26 08:00, Wei Liu wrote:
>>>>>> On Tue, Feb 03, 2026 at 05:01:30PM +0100, Jan Kiszka wrote:
>>>>>>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>>>>>>
>>>>>>> Resolves the following lockdep report when booting PREEMPT_RT on Hyper-V
>>>>>>> with related guest support enabled:
>>>>>>
>>>>>> So all it takes to reproduce this is to enabled PREEMPT_RT?
>>>>>>
>>>>>
>>>>> ...and enable CONFIG_PROVE_LOCKING so that you do not have to wait for
>>>>> your system to actually run into the bug. Lockdep already triggers
>>>>> during bootup.
>>>>>
>>>>>> Asking because ...
>>>>>>
>>>>>>> struct pt_regs *old_regs = set_irq_regs(regs);
>>>>>>> @@ -158,8 +196,12 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_callback)
>>>>>>> if (mshv_handler)
>>>>>>> mshv_handler();
>>>>>>
>>>>>> ... to err on the safe side we should probably do the same for
>>>>>> mshv_handler as well.
>>>>>>
>>>>>
>>>>> Valid question. We so far worked based on lockdep reports, and the
>>>>> mshv_handler didn't trigger yet. Either it is not run in our setup, or
>>>>> it is actually already fine. But I have a code review on my agenda
>>>>> regarding potential remaining issues in mshv.
>>>>>
>>>>> Is there something needed to trigger the mshv_handler so that we can
>>>>> test it?
>>>>>
>>>>
>>>> Ah, that depends on CONFIG_MSHV_ROOT. Is that related to the accelerator
>>>> mode that Magnus presented in [1]? We briefly chatted about it and also
>>>> my problems with the drivers after his talk on Saturday.
>>>
>>> Yes. That is the driver. If PROVE_LOCKING triggers the warning without
>>> running the code, perhaps turning on MSHV_ROOT is enough.
>>>
>>
>> But if my VM is not a root partition, I wouldn't use that driver, would I?
>
> No, you wouldn't. You cannot do that until later this year. If you
> cannot test that, so be it. I'm fine with applying your patch and then
> move the mshv_handler logic later ourselves.
>
> I've CC'ed a few folks from Microsoft.
>
> Saurabh, Long, and Dexuan, can you review and test this patch for VMBus?
I tested this and didn't see any issues with OpenHCL/mshv_vtl.
Regards,
Naman
next prev parent reply other threads:[~2026-02-06 7:33 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-03 16:01 [PATCH] x86: mshyperv: Use kthread for vmbus interrupts on PREEMPT_RT Jan Kiszka
2026-02-04 7:00 ` Wei Liu
2026-02-04 7:19 ` Jan Kiszka
2026-02-04 7:26 ` Jan Kiszka
2026-02-04 7:29 ` Wei Liu
2026-02-04 7:32 ` Jan Kiszka
2026-02-04 7:36 ` Wei Liu
2026-02-04 13:04 ` Jan Kiszka
2026-02-06 7:32 ` Naman Jain [this message]
2026-02-05 14:12 ` Bezdeka, Florian
2026-02-05 18:55 ` Michael Kelley
2026-02-06 6:40 ` Jan Kiszka
2026-02-07 1:30 ` Michael Kelley
2026-02-09 10:35 ` Florian Bezdeka
2026-02-09 18:25 ` Michael Kelley
2026-02-12 16:06 ` Jan Kiszka
2026-02-12 16:22 ` Michael Kelley
2026-02-13 21:35 ` mhklkml
2026-02-16 12:24 ` Jan Kiszka
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