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hisi_acc_vfio_pci: Remove the deferred_reset logic

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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: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Brett Creeley <brett.creeley@amd.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/20240229091152.56664-1-shameerali.kolothum.thodi@huawei.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Shameer Kolothum 2024-02-29 09:11:52 +00:00 committed by Alex Williamson
parent 5b99241277
commit fd94213e14
2 changed files with 14 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
View File

@ -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);
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);
}
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)

6
drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
View File

@ -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;
};