linux-kernel - Re: [PATCH v2] vfio: fix deadlock between group lock and kvm lock

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Date:   Thu, 2 Feb 2023 07:52:44 -0500
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        "farman@...ux.ibm.com" <farman@...ux.ibm.com>,
        "pmorel@...ux.ibm.com" <pmorel@...ux.ibm.com>,
        "borntraeger@...ux.ibm.com" <borntraeger@...ux.ibm.com>,
        "frankja@...ux.ibm.com" <frankja@...ux.ibm.com>,
        "imbrenda@...ux.ibm.com" <imbrenda@...ux.ibm.com>,
        "david@...hat.com" <david@...hat.com>,
        "akrowiak@...ux.ibm.com" <akrowiak@...ux.ibm.com>,
        "jjherne@...ux.ibm.com" <jjherne@...ux.ibm.com>,
        "pasic@...ux.ibm.com" <pasic@...ux.ibm.com>,
        "zhenyuw@...ux.intel.com" <zhenyuw@...ux.intel.com>,
        "Wang, Zhi A" <zhi.a.wang@...el.com>,
        "Christopherson, , Sean" <seanjc@...gle.com>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "intel-gvt-dev@...ts.freedesktop.org" 
        <intel-gvt-dev@...ts.freedesktop.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] vfio: fix deadlock between group lock and kvm lock

On 2/1/23 11:10 PM, Tian, Kevin wrote:
>> From: Alex Williamson <alex.williamson@...hat.com>
>> Sent: Thursday, February 2, 2023 7:28 AM
>>>
>>> +#ifdef CONFIG_HAVE_KVM
>>> +static bool vfio_kvm_get_kvm_safe(struct vfio_device *device, struct kvm
>> *kvm)
>>
>> I'm tempted to name these vfio_device_get_kvm_safe() and only pass the
>> vfio_device, where of course we can get the kvm pointer from the group
>> internally.
>>
> 
> I have a different thought. In the end the cdev series also need the similar
> safe get/put logic then it's better to keep it in vfio_main.c called by
> the group/cdev path individually.

Ah, I hadn't considered the cdev series - OK, I can move the functions back into vfio_main and externalize both via drivers/vfio/vfio.h so they can be called from group.c for this fix and then available to vfio_main.c already for cdev.