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

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Message-ID: <BN9PR11MB527649C5C0120F73DC8835528CD69@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Thu, 2 Feb 2023 04:07:25 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>
CC:     "pbonzini@...hat.com" <pbonzini@...hat.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

> From: Liu, Yi L <yi.l.liu@...el.com>
> Sent: Thursday, February 2, 2023 11:47 AM
> > >  	ret = vfio_device_open(device, device->group->iommufd,
> > >  			       device->group->kvm);
> >
> > We're using device->group->kvm outside of kvm_ref_lock here, it should
> > be using device->kvm.
> 
> Existing code set device->kvm in the vfio_device_first_open() which is
> called by vfio_device_open(). After above change, seems not necessary
> to pass kvm pointer into the call chain. Isn't it?
> 

Looks so.