Message-ID: <019a0cab-76b7-a3c0-d93f-5384efea1f67@huawei.com>
Date: Mon, 4 Nov 2024 16:31:18 +0800
From: liulongfang <liulongfang@...wei.com>
To: Alex Williamson <alex.williamson@...hat.com>
CC: <jgg@...dia.com>, <shameerali.kolothum.thodi@...wei.com>,
	<jonathan.cameron@...wei.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <linuxarm@...neuler.org>
Subject: Re: [PATCH v11 3/4] hisi_acc_vfio_pci: register debugfs for hisilicon
 migration driver

On 2024/11/4 15:54, liulongfang wrote:
> On 2024/11/1 6:04, Alex Williamson wrote:
>> On Fri, 25 Oct 2024 17:01:42 +0800
>> Longfang Liu <liulongfang@...wei.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@...wei.com>
>>> Reviewed-by: Shameer Kolothum <shameerali.kolothum.thodi@...wei.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.
>>
> 
> OK, delete it in next version.
> 
>>> +	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.
>>
> 
> OK, I will adjust it in the next version.
> 
>>> +			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.
>>
> 
> OK.
> 
>> 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.
>>
> 
> This QM_VF_STATE register will be written to QM_READY when the acc device
> driver is loaded, and QM_NOT_READY will be written after the device
> driver is unloaded.
>> I will add a comment where vf_qm_state is declared.
> 
>> What's the purpose of the "acc device:" prefix?
>>
> 
> OK, it can be deleted.
> 
>>> +
>>> +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.
>>
> 
> OK.
> 
>>> +
>>> +	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.
>>
> 
> The benefit of dev_opened retention is that user can obtain the device status
> during the cat migf_data operation.
>

I will remove dev_opened in the next version.
And hisi_acc_vdev->vf_qm_state is changed to debug_migf->vf_data.vf_qm_state
Keep information about whether the device driver in the Guest OS is loaded
when live migration occurs.

Thanks，
Longfang.

> And vf_qm_state does need to be retained.
> Because adding a driver or not adding a driver to the Guest OS has a great impact
> on the results of live migration, it is a key factor. It has a great impact on
> the success or failure of live migration.
> 
> When adding a driver, live migration will read device status data, and data will
> be written back to device after the migration is completed.
> When no driver is added, live migration only executes a process. It does not
> perform data reading and data recovery operations.
> 
>>> +
>>> +	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.
>>
> 
> OK, It will be deleted. Comments will also be updated.
> 
>>> +		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.
>>
> 
> OK, the comments will be updated according to your instructions.
> 
>>> +	bool dev_opened;
>>
>> Seems like open_mutex would fit just as well here and have better
>> proximity to the data it protects.
>>
> 
> OK, I'm going to move it over here.
> 
>>>  
>>>  	/* 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,
>>
> 
> OK, the comments will be updated according to your instructions.
> 
> Thanks.
> Longfang.
> 
>> Alex
>>
>>> +	struct hisi_acc_vf_migration_file *debug_migf;
>>> +	struct mutex open_mutex;
>>>  };
>>>  #endif /* HISI_ACC_VFIO_PCI_H */
>>
>>
>> .
>>
> 
> .
> 

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