Re: [RFC v2 3/3] vfio-ccw: Release any channel program when releasing/removing vfio-ccw mdev

Eric Farman
2019-04-12T21:01:35Z

On 4/8/19 5:05 PM, Farhan Ali wrote:
> When releasing the vfio-ccw mdev, we currently do not release
> any existing channel program and it's pinned pages. This can
> lead to the following warning:
>
> [1038876.561565] WARNING: CPU: 2 PID: 144727 at drivers/vfio/vfio_iommu_type1.c:1494 vfio_sanity_check_pfn_list+0x40/0x70 [vfio_iommu_type1]
>
> ....
>
> 1038876.561921] Call Trace:
> [1038876.561935] ([<00000009897fb870>] 0x9897fb870)
> [1038876.561949] [<000003ff8013bf62>] vfio_iommu_type1_detach_group+0xda/0x2f0 [vfio_iommu_type1]
> [1038876.561965] [<000003ff8007b634>] __vfio_group_unset_container+0x64/0x190 [vfio]
> [1038876.561978] [<000003ff8007b87e>] vfio_group_put_external_user+0x26/0x38 [vfio]
> [1038876.562024] [<000003ff806fc608>] kvm_vfio_group_put_external_user+0x40/0x60 [kvm]
> [1038876.562045] [<000003ff806fcb9e>] kvm_vfio_destroy+0x5e/0xd0 [kvm]
> [1038876.562065] [<000003ff806f63fc>] kvm_put_kvm+0x2a4/0x3d0 [kvm]
> [1038876.562083] [<000003ff806f655e>] kvm_vm_release+0x36/0x48 [kvm]
> [1038876.562098] [<00000000003c2dc4>] __fput+0x144/0x228
> [1038876.562113] [<000000000016ee82>] task_work_run+0x8a/0xd8
> [1038876.562125] [<000000000014c7a8>] do_exit+0x5d8/0xd90
> [1038876.562140] [<000000000014d084>] do_group_exit+0xc4/0xc8
> [1038876.562155] [<000000000015c046>] get_signal+0x9ae/0xa68
> [1038876.562169] [<0000000000108d66>] do_signal+0x66/0x768
> [1038876.562185] [<0000000000b9e37e>] system_call+0x1ea/0x2d8
> [1038876.562195] 2 locks held by qemu-system-s39/144727:
> [1038876.562205] #0: 00000000537abaf9 (&container->group_lock){++++}, at: __vfio_group_unset_container+0x3c/0x190 [vfio]
> [1038876.562230] #1: 00000000670008b5 (&iommu->lock){+.+.}, at: vfio_iommu_type1_detach_group+0x36/0x2f0 [vfio_iommu_type1]
> [1038876.562250] Last Breaking-Event-Address:
> [1038876.562262] [<000003ff8013aa24>] vfio_sanity_check_pfn_list+0x3c/0x70 [vfio_iommu_type1]
> [1038876.562272] irq event stamp: 4236481
> [1038876.562287] hardirqs last enabled at (4236489): [<00000000001cee7a>] console_unlock+0x6d2/0x740
> [1038876.562299] hardirqs last disabled at (4236496): [<00000000001ce87e>] console_unlock+0xd6/0x740
> [1038876.562311] softirqs last enabled at (4234162): [<0000000000b9fa1e>] __do_softirq+0x556/0x598
> [1038876.562325] softirqs last disabled at (4234153): [<000000000014e4cc>] irq_exit+0xac/0x108
> [1038876.562337] ---[ end trace 6c96d467b1c3ca06 ]---
>
> Similarly we do not free the channel program when we are removing
> the vfio-ccw device. Let's fix this by resetting the device and freeing
> the channel program and pinned pages in the release path. For the remove
> path we can just quiesce the device, since in the remove path the mediated
> device is going away for good and so we don't need to do a full reset.
>
> Signed-off-by: Farhan Ali <alifm@linux.ibm.com>
> ---
> drivers/s390/cio/vfio_ccw_ops.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
> index ec2f796c..aacd528 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -133,11 +133,12 @@ static int vfio_ccw_mdev_remove(struct mdev_device *mdev)
>
> if ((private->state != VFIO_CCW_STATE_NOT_OPER) &&
> (private->state != VFIO_CCW_STATE_STANDBY)) {
> - if (!vfio_ccw_mdev_reset(mdev))
> + if (!vfio_ccw_sch_quiesce(private->sch))
> private->state = VFIO_CCW_STATE_STANDBY;
> /* The state will be NOT_OPER on error. */
> }
>
> + cp_free(&private->cp);
> private->mdev = NULL;
> atomic_inc(&private->avail);
>
> @@ -171,6 +172,14 @@ static void vfio_ccw_mdev_release(struct mdev_device *mdev)
> dev_get_drvdata(mdev_parent_dev(mdev));
> int i;
>
> + if ((private->state != VFIO_CCW_STATE_NOT_OPER) &&
> + (private->state != VFIO_CCW_STATE_STANDBY)) {
> + if (!vfio_ccw_mdev_reset(mdev))
> + private->state = VFIO_CCW_STATE_STANDBY;
> + /* The state will be NOT_OPER on error. */
> + }
> +
> + cp_free(&private->cp);
> vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> &private->nb);
>
>

This seems sane to me.

Acked-by: Eric Farman <farman@linux.ibm.com>