Re: [PATCH v11 3/4] hisi_acc_vfio_pci: register debugfs for hisilicon migration driver

Alex Williamson
2024-10-31T22:04:36Z

On Fri, 25 Oct 2024 17:01:42 +0800
Longfang Liu <liulongfang@huawei.com> wrote:

> On the debugfs framework of VFIO, if the CONFIG_VFIO_DEBUGFS macro is
> enabled, the debug function is registered for the live migration driver
> of the HiSilicon accelerator device.
>
> After registering the HiSilicon accelerator device on the debugfs
> framework of live migration of vfio, a directory file "hisi_acc"
> of debugfs is created, and then three debug function files are
> created in this directory:
>
> vfio
> |
> +---<dev_name1>
> | +---migration
> | +--state
> | +--hisi_acc
> | +--dev_data
> | +--migf_data
> | +--cmd_state
> |
> +---<dev_name2>
> +---migration
> +--state
> +--hisi_acc
> +--dev_data
> +--migf_data
> +--cmd_state
>
> dev_data file: read device data that needs to be migrated from the
> current device in real time
> migf_data file: read the migration data of the last live migration
> from the current driver.
> cmd_state: used to get the cmd channel state for the device.
>
> +----------------+ +--------------+ +---------------+
> | migration dev | | src dev | | dst dev |
> +-------+--------+ +------+-------+ +-------+-------+
> | | |
> | +------v-------+ +-------v-------+
> | | saving_migf | | resuming_migf |
> read | | file | | file |
> | +------+-------+ +-------+-------+
> | | copy |
> | +------------+----------+
> | |
> +-------v--------+ +-------v--------+
> | data buffer | | debug_migf |
> +-------+--------+ +-------+--------+
> | |
> cat | cat |
> +-------v--------+ +-------v--------+
> | dev_data | | migf_data |
> +----------------+ +----------------+
>
> When accessing debugfs, user can obtain the most recent status data
> of the device through the "dev_data" file. It can read recent
> complete status data of the device. If the current device is being
> migrated, it will wait for it to complete.
> The data for the last completed migration function will be stored
> in debug_migf. Users can read it via "migf_data".
>
> Signed-off-by: Longfang Liu <liulongfang@huawei.com>
> Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
> ---
> .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c | 204 ++++++++++++++++++
> .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h | 7 +
> 2 files changed, 211 insertions(+)
>
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> index a8c53952d82e..0577d4ddfb34 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
> @@ -627,15 +627,30 @@ static void hisi_acc_vf_disable_fd(struct hisi_acc_vf_migration_file *migf)
> mutex_unlock(&migf->lock);
> }
>
> +static void hisi_acc_debug_migf_copy(struct hisi_acc_vf_core_device *hisi_acc_vdev,
> + struct hisi_acc_vf_migration_file *src_migf)
> +{
> + struct hisi_acc_vf_migration_file *dst_migf = hisi_acc_vdev->debug_migf;
> +
> + if (!dst_migf)
> + return;
> +
> + dst_migf->total_length = src_migf->total_length;
> + memcpy(&dst_migf->vf_data, &src_migf->vf_data,
> + sizeof(struct acc_vf_data));
> +}
> +
> static void hisi_acc_vf_disable_fds(struct hisi_acc_vf_core_device *hisi_acc_vdev)
> {
> if (hisi_acc_vdev->resuming_migf) {
> + hisi_acc_debug_migf_copy(hisi_acc_vdev, hisi_acc_vdev->resuming_migf);
> hisi_acc_vf_disable_fd(hisi_acc_vdev->resuming_migf);
> fput(hisi_acc_vdev->resuming_migf->filp);
> hisi_acc_vdev->resuming_migf = NULL;
> }
>
> if (hisi_acc_vdev->saving_migf) {
> + hisi_acc_debug_migf_copy(hisi_acc_vdev, hisi_acc_vdev->saving_migf);
> hisi_acc_vf_disable_fd(hisi_acc_vdev->saving_migf);
> fput(hisi_acc_vdev->saving_migf->filp);
> hisi_acc_vdev->saving_migf = NULL;
> @@ -1294,6 +1309,140 @@ static long hisi_acc_vfio_pci_ioctl(struct vfio_device *core_vdev, unsigned int
> return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> }
>
> +static int hisi_acc_vf_debug_check(struct seq_file *seq, struct vfio_device *vdev)
> +{
> + struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(vdev);
> + struct hisi_qm *vf_qm = &hisi_acc_vdev->vf_qm;
> + int ret;
> +
> + lockdep_assert_held(&hisi_acc_vdev->open_mutex);
> + /*
> + * When the device is not opened, the io_base is not mapped.
> + * The driver cannot perform device read and write operations.
> + */
> + if (!hisi_acc_vdev->dev_opened) {
> + seq_printf(seq, "device not opened!\n");
> + return -EINVAL;
> + }
> +
> + ret = qm_wait_dev_not_ready(vf_qm);
> + if (ret) {
> + seq_printf(seq, "VF device not ready!\n");
> + return -EBUSY;
> + }
> +
> + return 0;
> +}
> +
> +static int hisi_acc_vf_debug_cmd(struct seq_file *seq, void *data)
> +{
> + struct device *vf_dev = seq->private;
> + struct vfio_pci_core_device *core_device = dev_get_drvdata(vf_dev);
> + struct vfio_device *vdev = &core_device->vdev;
> + struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(vdev);
> + struct hisi_qm *vf_qm = &hisi_acc_vdev->vf_qm;
> + u64 value;
> + int ret;
> +
> + mutex_lock(&hisi_acc_vdev->open_mutex);
> + ret = hisi_acc_vf_debug_check(seq, vdev);
> + if (ret) {
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> + return ret;
> + }
> +
> + value = readl(vf_qm->io_base + QM_MB_CMD_SEND_BASE);
> + if (value == QM_MB_CMD_NOT_READY) {
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> + seq_printf(seq, "mailbox cmd channel not ready!\n");
> + return -EINVAL;
> + }
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> + seq_printf(seq, "mailbox cmd channel ready!\n");
> +
> + return 0;
> +}
> +
> +static int hisi_acc_vf_dev_read(struct seq_file *seq, void *data)
> +{
> + struct device *vf_dev = seq->private;
> + struct vfio_pci_core_device *core_device = dev_get_drvdata(vf_dev);
> + struct vfio_device *vdev = &core_device->vdev;
> + struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(vdev);
> + size_t vf_data_sz = offsetofend(struct acc_vf_data, padding);
> + struct acc_vf_data *vf_data = NULL;

Nit, this initialization is unnecessary.

> + int ret;
> +
> + mutex_lock(&hisi_acc_vdev->open_mutex);
> + ret = hisi_acc_vf_debug_check(seq, vdev);
> + if (ret) {
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> + return ret;
> + }
> +
> + mutex_lock(&hisi_acc_vdev->state_mutex);
> + vf_data = kzalloc(sizeof(struct acc_vf_data), GFP_KERNEL);
> + if (!vf_data) {
> + ret = -ENOMEM;
> + goto mutex_release;
> + }
> +
> + vf_data->vf_qm_state = hisi_acc_vdev->vf_qm_state;
> + ret = vf_qm_read_data(&hisi_acc_vdev->vf_qm, vf_data);
> + if (ret)
> + goto migf_err;
> +
> + seq_hex_dump(seq, "Dev Data:", DUMP_PREFIX_OFFSET, 16, 1,
> + (unsigned char *)vf_data,

Casting to (const void *) would match the prototype. This line should
also wrap to just inside the opening parenthesis of the previous line, 2
tabs, 5 spaces.

> + vf_data_sz, false);
> +
> + seq_printf(seq,
> + "acc device:\n"
> + "guest driver load: %u\n"
> + "data size: %lu\n",
> + hisi_acc_vdev->vf_qm_state,
> + sizeof(struct acc_vf_data));

Same here and throughout, wrap aligned to the relevant parenthesis.

I know you've described vf_qm_state as indicating whether or not the
guest driver is loaded, but I still can't figure out how to discern
that from the code. It's largely only set based on the return value of
qm_wait_dev_not_ready(), which tests QM_VF_STATE, and describes the
function as testing if the device is ready. Improved comments would
help future reviews.

What's the purpose of the "acc device:" prefix?

> +
> +migf_err:
> + kfree(vf_data);
> +mutex_release:
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> + mutex_unlock(&hisi_acc_vdev->state_mutex);

Locks should be released in the reverse order they were acquired.

> +
> + return ret;
> +}
> +
> +static int hisi_acc_vf_migf_read(struct seq_file *seq, void *data)
> +{
> + struct device *vf_dev = seq->private;
> + struct vfio_pci_core_device *core_device = dev_get_drvdata(vf_dev);
> + struct vfio_device *vdev = &core_device->vdev;
> + struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(vdev);
> + size_t vf_data_sz = offsetofend(struct acc_vf_data, padding);
> + struct hisi_acc_vf_migration_file *debug_migf = hisi_acc_vdev->debug_migf;
> +
> + /* Check whether the live migration operation has been performed */
> + if (debug_migf->total_length < QM_MATCH_SIZE) {
> + seq_printf(seq, "device not migrated!\n");
> + return -EAGAIN;
> + }
> +
> + seq_hex_dump(seq, "Mig Data:", DUMP_PREFIX_OFFSET, 16, 1,
> + (unsigned char *)&debug_migf->vf_data,
> + vf_data_sz, false);
> +
> + seq_printf(seq,
> + "acc device:\n"
> + "guest driver load: %u\n"
> + "device opened: %d\n"
> + "migrate data length: %lu\n",
> + hisi_acc_vdev->vf_qm_state,
> + hisi_acc_vdev->dev_opened,
> + debug_migf->total_length);

This debugfs entry is described as returning the data from the last
migration, but vf_qm_state and dev_opened are relative to the current
device/guest driver state. Both seem to have no relevance to the data
in debug_migf.

> +
> + return 0;
> +}
> +
> static int hisi_acc_vfio_pci_open_device(struct vfio_device *core_vdev)
> {
> struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(core_vdev);
> @@ -1305,12 +1454,16 @@ static int hisi_acc_vfio_pci_open_device(struct vfio_device *core_vdev)
> return ret;
>
> if (core_vdev->mig_ops) {
> + mutex_lock(&hisi_acc_vdev->open_mutex);
> ret = hisi_acc_vf_qm_init(hisi_acc_vdev);
> if (ret) {
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> vfio_pci_core_disable(vdev);
> return ret;
> }
> hisi_acc_vdev->mig_state = VFIO_DEVICE_STATE_RUNNING;
> + hisi_acc_vdev->dev_opened = true;
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> }
>
> vfio_pci_core_finish_enable(vdev);
> @@ -1322,7 +1475,10 @@ static void hisi_acc_vfio_pci_close_device(struct vfio_device *core_vdev)
> struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_get_vf_dev(core_vdev);
> struct hisi_qm *vf_qm = &hisi_acc_vdev->vf_qm;
>
> + mutex_lock(&hisi_acc_vdev->open_mutex);
> + hisi_acc_vdev->dev_opened = false;
> iounmap(vf_qm->io_base);
> + mutex_unlock(&hisi_acc_vdev->open_mutex);
> vfio_pci_core_close_device(core_vdev);
> }
>
> @@ -1342,6 +1498,7 @@ static int hisi_acc_vfio_pci_migrn_init_dev(struct vfio_device *core_vdev)
> hisi_acc_vdev->pf_qm = pf_qm;
> hisi_acc_vdev->vf_dev = pdev;
> mutex_init(&hisi_acc_vdev->state_mutex);
> + mutex_init(&hisi_acc_vdev->open_mutex);
>
> core_vdev->migration_flags = VFIO_MIGRATION_STOP_COPY | VFIO_MIGRATION_PRE_COPY;
> core_vdev->mig_ops = &hisi_acc_vfio_pci_migrn_state_ops;
> @@ -1387,6 +1544,50 @@ static const struct vfio_device_ops hisi_acc_vfio_pci_ops = {
> .detach_ioas = vfio_iommufd_physical_detach_ioas,
> };
>
> +static void hisi_acc_vfio_debug_init(struct hisi_acc_vf_core_device *hisi_acc_vdev)
> +{
> + struct vfio_device *vdev = &hisi_acc_vdev->core_device.vdev;
> + struct dentry *vfio_dev_migration = NULL;
> + struct dentry *vfio_hisi_acc = NULL;
> + struct device *dev = vdev->dev;
> + void *migf = NULL;
> +
> + if (!debugfs_initialized() ||
> + !IS_ENABLED(CONFIG_VFIO_DEBUGFS))
> + return;
> +
> + if (vdev->ops != &hisi_acc_vfio_pci_migrn_ops)
> + return;
> +
> + vfio_dev_migration = debugfs_lookup("migration", vdev->debug_root);
> + if (!vfio_dev_migration) {
> + dev_err(dev, "failed to lookup migration debugfs file!\n");
> + return;
> + }
> +
> + migf = kzalloc(sizeof(struct hisi_acc_vf_migration_file), GFP_KERNEL);
> + if (!migf)
> + return;
> + hisi_acc_vdev->debug_migf = migf;
> +
> + vfio_hisi_acc = debugfs_create_dir("hisi_acc", vfio_dev_migration);
> + debugfs_create_devm_seqfile(dev, "dev_data", vfio_hisi_acc,
> + hisi_acc_vf_dev_read);
> + debugfs_create_devm_seqfile(dev, "migf_data", vfio_hisi_acc,
> + hisi_acc_vf_migf_read);
> + debugfs_create_devm_seqfile(dev, "cmd_state", vfio_hisi_acc,
> + hisi_acc_vf_debug_cmd);
> +}
> +
> +static void hisi_acc_vf_debugfs_exit(struct hisi_acc_vf_core_device *hisi_acc_vdev)
> +{
> + /* If migrn_ops is not used, debug_migf is NULL */
> + if (hisi_acc_vdev->debug_migf) {

This test is unnecessary, kfree(NULL) is valid.

> + kfree(hisi_acc_vdev->debug_migf);
> + hisi_acc_vdev->debug_migf = NULL;
> + }
> +}
> +
> static int hisi_acc_vfio_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> {
> struct hisi_acc_vf_core_device *hisi_acc_vdev;
> @@ -1413,6 +1614,8 @@ static int hisi_acc_vfio_pci_probe(struct pci_dev *pdev, const struct pci_device
> ret = vfio_pci_core_register_device(&hisi_acc_vdev->core_device);
> if (ret)
> goto out_put_vdev;
> +
> + hisi_acc_vfio_debug_init(hisi_acc_vdev);
> return 0;
>
> out_put_vdev:
> @@ -1425,6 +1628,7 @@ static void hisi_acc_vfio_pci_remove(struct pci_dev *pdev)
> struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_drvdata(pdev);
>
> vfio_pci_core_unregister_device(&hisi_acc_vdev->core_device);
> + hisi_acc_vf_debugfs_exit(hisi_acc_vdev);
> vfio_put_device(&hisi_acc_vdev->core_device.vdev);
> }
>
> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> index 5bab46602fad..2a78ffd060c3 100644
> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
> @@ -32,6 +32,7 @@
> #define QM_SQC_VFT_BASE_MASK_V2 GENMASK(15, 0)
> #define QM_SQC_VFT_NUM_SHIFT_V2 45
> #define QM_SQC_VFT_NUM_MASK_V2 GENMASK(9, 0)
> +#define QM_MB_CMD_NOT_READY 0xffffffff
>
> /* RW regs */
> #define QM_REGS_MAX_LEN 7
> @@ -99,6 +100,8 @@ struct hisi_acc_vf_migration_file {
> struct hisi_acc_vf_core_device {
> struct vfio_pci_core_device core_device;
> u8 match_done;
> + /* To make sure the device is opened */

We can infer that from the field name, it would be more useful to
comment that io_base is only valid when dev_opened, which is protected
by open_mutex.

> + bool dev_opened;

Seems like open_mutex would fit just as well here and have better
proximity to the data it protects.

>
> /* For migration state */
> struct mutex state_mutex;
> @@ -111,5 +114,9 @@ struct hisi_acc_vf_core_device {
> int vf_id;
> struct hisi_acc_vf_migration_file *resuming_migf;
> struct hisi_acc_vf_migration_file *saving_migf;
> +
> + /* To save migration data */

Clearly. Describing it as an extra buffer for reporting migration data
through debugfs might be more useful. Thanks,

Alex

> + struct hisi_acc_vf_migration_file *debug_migf;
> + struct mutex open_mutex;
> };
> #endif /* HISI_ACC_VFIO_PCI_H */