linux-kernel - Re: [PATCH v3 vfio 1/3] pds/vfio: Fix spinlock bad magic BUG

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Message-ID: <95851979-fa65-7bf8-2d62-ee3f3797a167@amd.com>
Date:   Wed, 1 Nov 2023 12:18:29 -0700
From:   Brett Creeley <bcreeley@....com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Brett Creeley <brett.creeley@....com>,
        "jgg@...pe.ca" <jgg@...pe.ca>,
        "yishaih@...dia.com" <yishaih@...dia.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "dan.carpenter@...aro.org" <dan.carpenter@...aro.org>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "shannon.nelson@....com" <shannon.nelson@....com>
Subject: Re: [PATCH v3 vfio 1/3] pds/vfio: Fix spinlock bad magic BUG



On 10/30/2023 11:13 PM, Tian, Kevin wrote:
> Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.
> 
> 
>> From: Brett Creeley <brett.creeley@....com>
>> Sent: Saturday, October 28, 2023 6:37 AM
>>
>> The following BUG was found when running on a kernel with
>> CONFIG_DEBUG_SPINLOCK=y set:
>>
>> BUG: spinlock bad magic on CPU#2, bash/2481
>>   lock: 0xffff8d6052a88f50, .magic: 00000000, .owner: <none>/-1, .owner_cpu:
>> 0
>> Call Trace:
>>   <TASK>
>>   dump_stack_lvl+0x36/0x50
>>   do_raw_spin_lock+0x79/0xc0
>>   pds_vfio_reset+0x1d/0x60 [pds_vfio_pci]
>>   pci_reset_function+0x4b/0x70
>>   reset_store+0x5b/0xa0
>>   kernfs_fop_write_iter+0x137/0x1d0
>>   vfs_write+0x2de/0x410
>>   ksys_write+0x5d/0xd0
>>   do_syscall_64+0x3b/0x90
>>   entry_SYSCALL_64_after_hwframe+0x6e/0xd8
>>
>> As shown, the .magic: 00000000, does not match the expected value. This
>> is because spin_lock_init() is never called for the reset_lock. Fix
>> this by calling spin_lock_init(&pds_vfio->reset_lock) when initializing
>> the device.
>>
>> Signed-off-by: Brett Creeley <brett.creeley@....com>
>> Reviewed-by: Shannon Nelson <shannon.nelson@....com>
> 
> is this patch still required with patch3?

Good point. It's not required anymore since there is no spinlock.

Thanks,

Brett