Re: [PATCH 2/3] hisi_acc_vfio_pci: register debugfs for hisilicon migration driver

[liulongfang]

On 2024/1/26 6:38, Alex Williamson wrote:
> On Thu, 25 Jan 2024 16:10:30 +0800
> Longfang Liu <liulongfang@xxxxxxxxxx> 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
>>     |            +--attr
>>     |            +--data
>>     |            +--save
>>     |            +--cmd_state
>>     |
>>     +---<dev_name2>
>>          +---migration
>>              +--state
>>              +--hisi_acc
>>                  +--attr
>>                  +--data
>>                  +--save
>>                  +--cmd_state
>>
>> data file: used to get the migration data from the driver
>> attr file: used to get device attributes parameters from the driver
>> save file: used to read the data of the live migration device and save
>> it to the driver.
>> cmd_state: used to get the cmd channel state for the device.
>>
>> Signed-off-by: Longfang Liu <liulongfang@xxxxxxxxxx>
>> ---
>>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    | 190 ++++++++++++++++++
>>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h    |   5 +
>>  2 files changed, 195 insertions(+)
>>
>> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> index 5f6e01571a7b..2cbbc52b7377 100644
>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> @@ -15,6 +15,7 @@
>>  #include <linux/anon_inodes.h>
>>  
>>  #include "hisi_acc_vfio_pci.h"
>> +#include "../../vfio.h"
>>  
>>  /* Return 0 on VM acc device ready, -ETIMEDOUT hardware timeout */
>>  static int qm_wait_dev_not_ready(struct hisi_qm *qm)
>> @@ -617,6 +618,18 @@ hisi_acc_check_int_state(struct hisi_acc_vf_core_device *hisi_acc_vdev)
>>  	}
>>  }
>>  
>> +static void hisi_acc_vf_migf_save(struct hisi_acc_vf_migration_file *dst_migf,
>> +	struct hisi_acc_vf_migration_file *src_migf)
>> +{
>> +	if (!dst_migf)
>> +		return;
>> +
>> +	dst_migf->disabled = false;
>> +	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_fd(struct hisi_acc_vf_migration_file *migf)
>>  {
>>  	mutex_lock(&migf->lock);
>> @@ -629,12 +642,16 @@ static void hisi_acc_vf_disable_fd(struct hisi_acc_vf_migration_file *migf)
>>  static void hisi_acc_vf_disable_fds(struct hisi_acc_vf_core_device *hisi_acc_vdev)
>>  {
>>  	if (hisi_acc_vdev->resuming_migf) {
>> +		hisi_acc_vf_migf_save(hisi_acc_vdev->debug_migf,
>> +						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_vf_migf_save(hisi_acc_vdev->debug_migf,
>> +						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;
>> @@ -1175,6 +1192,7 @@ static int hisi_acc_vf_qm_init(struct hisi_acc_vf_core_device *hisi_acc_vdev)
>>  	if (!vf_qm->io_base)
>>  		return -EIO;
>>  
>> +	mutex_init(&hisi_acc_vdev->enable_mutex);
>>  	vf_qm->fun_type = QM_HW_VF;
>>  	vf_qm->pdev = vf_dev;
>>  	mutex_init(&vf_qm->mailbox_lock);
>> @@ -1325,6 +1343,172 @@ 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_acc_vf_migration_file *migf = hisi_acc_vdev->debug_migf;
>> +
>> +	if (!vdev->mig_ops || !migf) {
>> +		seq_printf(seq, "%s\n", "device does not support live migration!");
>> +		return -EINVAL;
>> +	}
>> +
>> +	/**
>> +	 * When the device is not opened, the io_base is not mapped.
>> +	 * The driver cannot perform device read and write operations.
>> +	 */
>> +	if (!vdev->open_count) {
>> +		seq_printf(seq, "%s\n", "device not opened!");
>> +		return -EINVAL;
>> +	}
> 
> This is racy, this check could occur while the user is already closing
> the device and vfio_df_device_last_close() may have already iounmap'd
> the io_base.  Only after that is open_count decremented.  The debugfs
> interfaces would then proceed to access the unmapped space.  The
> enable_mutex is entirely ineffective (and also asymmetric, initialized
> in the open_device path but never destroyed).
> 
> In fact, the enable_mutex really only seems to be trying to protect
> io_base (which it doesn't do), meanwhile the core driver execution path
> can run concurrently to debugfs operations with no serialization.  It
> looks like these operations would step on each other.
>

Yes, this enable_mutex is used to protect io_base. It prevents debugfs
from being used after executing iounmap in io_base.

> I think you might need an atomic to guard against io_base unmapping and
> then maybe a mutex or semaphore to avoid debugfs accesses from
> interfering with the actual core logic interacting with the device.
> Thanks,
>

OK An atomic variable needs to be added to replace vdev->open_count to prevent
competition. And use enable_mutex to prevent io_base from being released early.


Thanks,
Longfang.

> Alex
> 
>> +
>> +	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;
>> +
>> +	ret = hisi_acc_vf_debug_check(seq, vdev);
>> +	if (ret)
>> +		return 0;
>> +
>> +	mutex_lock(&hisi_acc_vdev->enable_mutex);
>> +	ret = qm_wait_dev_not_ready(vf_qm);
>> +	if (ret) {
>> +		mutex_unlock(&hisi_acc_vdev->enable_mutex);
>> +		seq_printf(seq, "%s\n", "VF device not ready!");
>> +		return 0;
>> +	}
>> +
>> +	value = readl(vf_qm->io_base + QM_MB_CMD_SEND_BASE);
>> +	mutex_unlock(&hisi_acc_vdev->enable_mutex);
>> +	seq_printf(seq, "%s:0x%llx\n", "mailbox cmd channel state is OK", value);
>> +
>> +	return 0;
>> +}
>> +
>> +static int hisi_acc_vf_debug_save(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_acc_vf_migration_file *migf = hisi_acc_vdev->debug_migf;
>> +	int ret;
>> +
>> +	ret = hisi_acc_vf_debug_check(seq, vdev);
>> +	if (ret)
>> +		return 0;
>> +
>> +	mutex_lock(&hisi_acc_vdev->enable_mutex);
>> +	ret = vf_qm_state_save(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		mutex_unlock(&hisi_acc_vdev->enable_mutex);
>> +		seq_printf(seq, "%s\n", "failed to save device data!");
>> +		return 0;
>> +	}
>> +	mutex_unlock(&hisi_acc_vdev->enable_mutex);
>> +	seq_printf(seq, "%s\n", "successful to save device data!");
>> +
>> +	return 0;
>> +}
>> +
>> +static int hisi_acc_vf_data_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);
>> +	struct hisi_acc_vf_migration_file *debug_migf = hisi_acc_vdev->debug_migf;
>> +	size_t vf_data_sz = offsetofend(struct acc_vf_data, padding);
>> +
>> +	if (debug_migf && debug_migf->total_length)
>> +		seq_hex_dump(seq, "Mig Data:", DUMP_PREFIX_OFFSET, 16, 1,
>> +				(unsigned char *)&debug_migf->vf_data,
>> +				vf_data_sz, false);
>> +	else
>> +		seq_printf(seq, "%s\n", "device not migrated!");
>> +
>> +	return 0;
>> +}
>> +
>> +static int hisi_acc_vf_attr_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);
>> +	struct hisi_acc_vf_migration_file *debug_migf = hisi_acc_vdev->debug_migf;
>> +
>> +	if (debug_migf && debug_migf->total_length) {
>> +		seq_printf(seq,
>> +			 "acc device:\n"
>> +			 "device  state: %d\n"
>> +			 "device  ready: %u\n"
>> +			 "data    valid: %d\n"
>> +			 "data     size: %lu\n",
>> +			 hisi_acc_vdev->mig_state,
>> +			 hisi_acc_vdev->vf_qm_state,
>> +			 debug_migf->disabled,
>> +			 debug_migf->total_length);
>> +	} else {
>> +		seq_printf(seq, "%s\n", "device not migrated!");
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int 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())
>> +		return 0;
>> +
>> +	migf = kzalloc(sizeof(struct hisi_acc_vf_migration_file), GFP_KERNEL);
>> +	if (!migf)
>> +		return -ENOMEM;
>> +	hisi_acc_vdev->debug_migf = migf;
>> +
>> +	vfio_dev_migration = debugfs_lookup("migration", vdev->debug_root);
>> +	if (!vfio_dev_migration) {
>> +		kfree(migf);
>> +		dev_err(dev, "failed to lookup migration debugfs file!\n");
>> +		return -ENODEV;
>> +	}
>> +
>> +	vfio_hisi_acc = debugfs_create_dir("hisi_acc", vfio_dev_migration);
>> +	debugfs_create_devm_seqfile(dev, "data", vfio_hisi_acc,
>> +				  hisi_acc_vf_data_read);
>> +	debugfs_create_devm_seqfile(dev, "attr", vfio_hisi_acc,
>> +				  hisi_acc_vf_attr_read);
>> +	debugfs_create_devm_seqfile(dev, "cmd_state", vfio_hisi_acc,
>> +				  hisi_acc_vf_debug_cmd);
>> +	debugfs_create_devm_seqfile(dev, "save", vfio_hisi_acc,
>> +				  hisi_acc_vf_debug_save);
>> +
>> +	return 0;
>> +}
>> +
>> +static void hisi_acc_vf_debugfs_exit(struct hisi_acc_vf_core_device *hisi_acc_vdev)
>> +{
>> +	if (!debugfs_initialized())
>> +		return;
>> +
>> +	kfree(hisi_acc_vdev->debug_migf);
>> +}
>> +
>>  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);
>> @@ -1353,7 +1537,9 @@ 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->enable_mutex);
>>  	iounmap(vf_qm->io_base);
>> +	mutex_unlock(&hisi_acc_vdev->enable_mutex);
>>  	vfio_pci_core_close_device(core_vdev);
>>  }
>>  
>> @@ -1444,6 +1630,9 @@ 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;
>> +
>> +	if (ops == &hisi_acc_vfio_pci_migrn_ops)
>> +		hisi_acc_vfio_debug_init(hisi_acc_vdev);
>>  	return 0;
>>  
>>  out_put_vdev:
>> @@ -1456,6 +1645,7 @@ 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 c58fc5861492..38327b97d535 100644
>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
>> @@ -116,5 +116,10 @@ struct hisi_acc_vf_core_device {
>>  	spinlock_t reset_lock;
>>  	struct hisi_acc_vf_migration_file *resuming_migf;
>>  	struct hisi_acc_vf_migration_file *saving_migf;
>> +
>> +	/* To make sure the device is enabled */
>> +	struct mutex enable_mutex;
>> +	/* For debugfs */
>> +	struct hisi_acc_vf_migration_file *debug_migf;
>>  };
>>  #endif /* HISI_ACC_VFIO_PCI_H */
> 
> .
>