Commit fd94213e authored by Shameer Kolothum's avatar Shameer Kolothum Committed by Alex Williamson
Browse files

hisi_acc_vfio_pci: Remove the deferred_reset logic 

The deferred_reset logic was added to vfio migration drivers to prevent
a circular locking dependency with respect to mm_lock and state mutex.
This is mainly because of the copy_to/from_user() functions(which takes
mm_lock) invoked under state mutex. But for HiSilicon driver, the only
place where we now hold the state mutex for copy_to_user is during the
PRE_COPY IOCTL. So for pre_copy, release the lock as soon as we have
updated the data and perform copy_to_user without state mutex. By this,
we can get rid of the deferred_reset logic.

Link: https://lore.kernel.org/kvm/20240220132459.GM13330@nvidia.com/


Signed-off-by: default avatarShameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: default avatarBrett Creeley <brett.creeley@amd.com>
Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240229091152.56664-1-shameerali.kolothum.thodi@huawei.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 5b992412

drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c

+12 −36
Original line number Diff line number Diff line
@@ -630,25 +630,11 @@ static void hisi_acc_vf_disable_fds(struct hisi_acc_vf_core_device *hisi_acc_vde 
	}

}



/*

 * This function is called in all state_mutex unlock cases to

 * handle a 'deferred_reset' if exists.

 */

static void

hisi_acc_vf_state_mutex_unlock(struct hisi_acc_vf_core_device *hisi_acc_vdev)

static void hisi_acc_vf_reset(struct hisi_acc_vf_core_device *hisi_acc_vdev)

{

again:

	spin_lock(&hisi_acc_vdev->reset_lock);

	if (hisi_acc_vdev->deferred_reset) {

		hisi_acc_vdev->deferred_reset = false;

		spin_unlock(&hisi_acc_vdev->reset_lock);

	hisi_acc_vdev->vf_qm_state = QM_NOT_READY;

	hisi_acc_vdev->mig_state = VFIO_DEVICE_STATE_RUNNING;

	hisi_acc_vf_disable_fds(hisi_acc_vdev);

		goto again;

	}

	mutex_unlock(&hisi_acc_vdev->state_mutex);

	spin_unlock(&hisi_acc_vdev->reset_lock);

}



static void hisi_acc_vf_start_device(struct hisi_acc_vf_core_device *hisi_acc_vdev)
@@ -804,8 +790,10 @@ static long hisi_acc_vf_precopy_ioctl(struct file *filp, 


	info.dirty_bytes = 0;

	info.initial_bytes = migf->total_length - *pos;

	mutex_unlock(&migf->lock);

	mutex_unlock(&hisi_acc_vdev->state_mutex);



	ret = copy_to_user((void __user *)arg, &info, minsz) ? -EFAULT : 0;

	return copy_to_user((void __user *)arg, &info, minsz) ? -EFAULT : 0;

out:

	mutex_unlock(&migf->lock);

	mutex_unlock(&hisi_acc_vdev->state_mutex);
@@ -1071,7 +1059,7 @@ hisi_acc_vfio_pci_set_device_state(struct vfio_device *vdev, 
			break;

		}

	}

	hisi_acc_vf_state_mutex_unlock(hisi_acc_vdev);

	mutex_unlock(&hisi_acc_vdev->state_mutex);

	return res;

}
@@ -1092,7 +1080,7 @@ hisi_acc_vfio_pci_get_device_state(struct vfio_device *vdev, 


	mutex_lock(&hisi_acc_vdev->state_mutex);

	*curr_state = hisi_acc_vdev->mig_state;

	hisi_acc_vf_state_mutex_unlock(hisi_acc_vdev);

	mutex_unlock(&hisi_acc_vdev->state_mutex);

	return 0;

}
@@ -1104,21 +1092,9 @@ static void hisi_acc_vf_pci_aer_reset_done(struct pci_dev *pdev) 
				VFIO_MIGRATION_STOP_COPY)

		return;



	/*

	 * As the higher VFIO layers are holding locks across reset and using

	 * those same locks with the mm_lock we need to prevent ABBA deadlock

	 * with the state_mutex and mm_lock.

	 * In case the state_mutex was taken already we defer the cleanup work

	 * to the unlock flow of the other running context.

	 */

	spin_lock(&hisi_acc_vdev->reset_lock);

	hisi_acc_vdev->deferred_reset = true;

	if (!mutex_trylock(&hisi_acc_vdev->state_mutex)) {

		spin_unlock(&hisi_acc_vdev->reset_lock);

		return;

	}

	spin_unlock(&hisi_acc_vdev->reset_lock);

	hisi_acc_vf_state_mutex_unlock(hisi_acc_vdev);

	mutex_lock(&hisi_acc_vdev->state_mutex);

	hisi_acc_vf_reset(hisi_acc_vdev);

	mutex_unlock(&hisi_acc_vdev->state_mutex);

}



static int hisi_acc_vf_qm_init(struct hisi_acc_vf_core_device *hisi_acc_vdev)

drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h

+2 −4
Original line number Diff line number Diff line
@@ -98,8 +98,8 @@ struct hisi_acc_vf_migration_file { 


struct hisi_acc_vf_core_device {

	struct vfio_pci_core_device core_device;

	u8 match_done:1;

	u8 deferred_reset:1;

	u8 match_done;



	/* For migration state */

	struct mutex state_mutex;

	enum vfio_device_mig_state mig_state;
@@ -109,8 +109,6 @@ struct hisi_acc_vf_core_device { 
	struct hisi_qm vf_qm;

	u32 vf_qm_state;

	int vf_id;

	/* For reset handler */

	spinlock_t reset_lock;

	struct hisi_acc_vf_migration_file *resuming_migf;

	struct hisi_acc_vf_migration_file *saving_migf;

};