From: Jason Gunthorpe <jgg@nvidia.com>
To: Matthew Rosato <mjrosato@linux.ibm.com>
Cc: akrowiak@linux.ibm.com, jjherne@linux.ibm.com,
farman@linux.ibm.com, imbrenda@linux.ibm.com,
frankja@linux.ibm.com, pmorel@linux.ibm.com, david@redhat.com,
seanjc@google.com, intel-gfx@lists.freedesktop.org,
cohuck@redhat.com, linux-kernel@vger.kernel.org,
pasic@linux.ibm.com, kvm@vger.kernel.org, pbonzini@redhat.com,
linux-s390@vger.kernel.org, borntraeger@linux.ibm.com,
intel-gvt-dev@lists.freedesktop.org
Subject: Re: [Intel-gfx] [PATCH v3] vfio: fix potential deadlock on vfio group lock
Date: Fri, 13 Jan 2023 14:52:56 -0400 [thread overview]
Message-ID: <Y8GoiCBQNiAuVcNw@nvidia.com> (raw)
In-Reply-To: <20230113171132.86057-1-mjrosato@linux.ibm.com>
On Fri, Jan 13, 2023 at 12:11:32PM -0500, Matthew Rosato wrote:
> @@ -462,9 +520,19 @@ static inline void vfio_device_pm_runtime_put(struct vfio_device *device)
> static int vfio_device_fops_release(struct inode *inode, struct file *filep)
> {
> struct vfio_device *device = filep->private_data;
> + struct kvm *kvm = NULL;
>
> vfio_device_group_close(device);
>
> + mutex_lock(&device->dev_set->lock);
> + if (device->open_count == 0 && device->kvm) {
> + kvm = device->kvm;
> + device->kvm = NULL;
> + }
> + mutex_unlock(&device->dev_set->lock);
This still doesn't seem right, another thread could have incr'd the
open_count already
This has to be done at the moment open_count is decremented to zero,
while still under the original lock.
Jason
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Matthew Rosato <mjrosato@linux.ibm.com>
Cc: alex.williamson@redhat.com, pbonzini@redhat.com,
cohuck@redhat.com, farman@linux.ibm.com, pmorel@linux.ibm.com,
borntraeger@linux.ibm.com, frankja@linux.ibm.com,
imbrenda@linux.ibm.com, david@redhat.com, akrowiak@linux.ibm.com,
jjherne@linux.ibm.com, pasic@linux.ibm.com,
zhenyuw@linux.intel.com, zhi.a.wang@intel.com, seanjc@google.com,
linux-s390@vger.kernel.org, kvm@vger.kernel.org,
intel-gvt-dev@lists.freedesktop.org,
intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] vfio: fix potential deadlock on vfio group lock
Date: Fri, 13 Jan 2023 14:52:56 -0400 [thread overview]
Message-ID: <Y8GoiCBQNiAuVcNw@nvidia.com> (raw)
In-Reply-To: <20230113171132.86057-1-mjrosato@linux.ibm.com>
On Fri, Jan 13, 2023 at 12:11:32PM -0500, Matthew Rosato wrote:
> @@ -462,9 +520,19 @@ static inline void vfio_device_pm_runtime_put(struct vfio_device *device)
> static int vfio_device_fops_release(struct inode *inode, struct file *filep)
> {
> struct vfio_device *device = filep->private_data;
> + struct kvm *kvm = NULL;
>
> vfio_device_group_close(device);
>
> + mutex_lock(&device->dev_set->lock);
> + if (device->open_count == 0 && device->kvm) {
> + kvm = device->kvm;
> + device->kvm = NULL;
> + }
> + mutex_unlock(&device->dev_set->lock);
This still doesn't seem right, another thread could have incr'd the
open_count already
This has to be done at the moment open_count is decremented to zero,
while still under the original lock.
Jason
next prev parent reply other threads:[~2023-01-13 18:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-13 17:11 [Intel-gfx] [PATCH v3] vfio: fix potential deadlock on vfio group lock Matthew Rosato
2023-01-13 17:11 ` Matthew Rosato
2023-01-13 17:54 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for vfio: fix potential deadlock on vfio group lock (rev2) Patchwork
2023-01-13 18:52 ` Jason Gunthorpe [this message]
2023-01-13 18:52 ` [PATCH v3] vfio: fix potential deadlock on vfio group lock Jason Gunthorpe
2023-01-13 20:09 ` [Intel-gfx] " Matthew Rosato
2023-01-13 20:09 ` Matthew Rosato
2023-01-13 20:18 ` [Intel-gfx] " Jason Gunthorpe
2023-01-13 20:18 ` Jason Gunthorpe
2023-01-13 23:47 ` [Intel-gfx] ✓ Fi.CI.BAT: success for vfio: fix potential deadlock on vfio group lock (rev2) Patchwork
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