RE: [PATCH] x86/hyper-v: guard against cpu mask changes in hyperv_flush_tlb_others()

This is not visible since we need a very high load to reproduce. 
We have tried a lot but can't achieve the desired load 
On our kernel with less load, it is not reproducible as well.

-----Original Message-----
From: Wei Liu <wei.liu@kernel.org> 
Sent: Sunday, August 22, 2021 6:25 PM
To: David Mozes <redacted>
Cc: David Moses <redacted>; Wei Liu <wei.liu@kernel.org>; Michael Kelley <redacted>; תומר אבוטבול <redacted>; linux-hyperv@vger.kernel.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86/hyper-v: guard against cpu mask changes in hyperv_flush_tlb_others()

On Thu, Aug 19, 2021 at 07:55:06AM +0000, David Mozes wrote:

Hi Wei ,
I move the print cpumask to other two places after the treatment on the empty mask see below
And I got the folwing:


Aug 19 02:01:51 c-node05 kernel: [25936.562674] Hyper-V: ERROR_HYPERV2: cpu_last=
Aug 19 02:01:51 c-node05 kernel: [25936.562686] WARNING: CPU: 11 PID: 56432 at arch/x86/include/asm/mshyperv.h:301 hyperv_flush_tlb_others+0x23f/0x7b0

So we got empty on different place on the code .
Let me know if you need further information from us.
How you sagest to handle this situation?

Please find a way to reproduce this issue with upstream kernels.

Thanks,
Wei.