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@xxxxxxxxxx/ Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx> --- .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c | 48 +++++-------------- .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h | 6 +-- 2 files changed, 14 insertions(+), 40 deletions(-) diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c index 4d27465c8f1a..9a3e97108ace 100644 --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c @@ -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) diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h index dcabfeec6ca1..5bab46602fad 100644 --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h @@ -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; }; -- 2.34.1
