linux-kernel - Re: [PATCH v2 vfio 0/3] pds/vfio: Fixes for locking bugs

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Message-ID: <2cd89c2c-96fc-8395-2c44-5804fe5c6594@amd.com>
Date:   Mon, 16 Oct 2023 07:49:53 -0700
From:   Brett Creeley <bcreeley@....com>
To:     Alex Williamson <alex.williamson@...hat.com>,
        Brett Creeley <brett.creeley@....com>
Cc:     jgg@...pe.ca, yishaih@...dia.com,
        shameerali.kolothum.thodi@...wei.com, kevin.tian@...el.com,
        dan.carpenter@...aro.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, shannon.nelson@....com
Subject: Re: [PATCH v2 vfio 0/3] pds/vfio: Fixes for locking bugs

On 10/13/2023 2:09 PM, Alex Williamson wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
> On Wed, 11 Oct 2023 16:01:12 -0700
> Brett Creeley <brett.creeley@....com> wrote:
> 
>> This series contains fixes for locking bugs in the recently introduced
>> pds-vfio-pci driver. There was an initial bug reported by Dan Carpenter
>> at:
>>
>> https://lore.kernel.org/kvm/1f9bc27b-3de9-4891-9687-ba2820c1b390@moroto.mountain/
>>
>> However, more locking bugs were found when looking into the previously
>> mentioned issue. So, all fixes are included in this series.
>>
>> v2:
>> https://lore.kernel.org/kvm/20230914191540.54946-1-brett.creeley@amd.com/
>> - Trim the OOPs in the patch commit messages
>> - Rework patch 3/3 to only unlock the spinlock once
> 
> I thought we determined the spinlock, and thus the atomic context, was
> an arbitrary choice.  I would have figured we simply convert it to a
> mutex.  Why didn't we take that route?  Thanks,
> 
> Alex

Hmm. I guess it wasn't completely clear that was the expected solution 
even after Jason's response. However, I can resubmit a v3 with that change.

Thanks,

Brett
> 
>> - Destroy the state_mutex in the driver specific vfio_device_ops.release
>>    callback
>>
>> Brett Creeley (3):
>>    pds/vfio: Fix spinlock bad magic BUG
>>    pds/vfio: Fix mutex lock->magic != lock warning
>>    pds/vfio: Fix possible sleep while in atomic context
>>
>>   drivers/vfio/pci/pds/vfio_dev.c | 27 ++++++++++++++++++++-------
>>   1 file changed, 20 insertions(+), 7 deletions(-)
>>
>