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Subject: Re: [PATCH v9 3/5] hisi_acc_vfio_pci: register debugfs for hisilicon
 migration driver
To:     Alex Williamson <alex.williamson@redhat.com>
CC:     <jgg@nvidia.com>, <shameerali.kolothum.thodi@huawei.com>,
        <jonathan.cameron@huawei.com>, <cohuck@redhat.com>,
        <linux-kernel@vger.kernel.org>, <linuxarm@openeuler.org>
References: <20230320092338.2889-1-liulongfang@huawei.com>
 <20230320092338.2889-4-liulongfang@huawei.com>
 <20230320160900.4e2eaebd.alex.williamson@redhat.com>
From:   liulongfang <liulongfang@huawei.com>
Message-ID: <9e28c25e-5a1d-bf10-f7e8-71a0f4d552a5@huawei.com>
Date:   Sat, 25 Mar 2023 17:39:17 +0800
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On 2023/3/21 6:09, Alex Williamson wrote:
> On Mon, 20 Mar 2023 17:23:36 +0800
> Longfang Liu <liulongfang@huawei.com> wrote:
> 
>> On the debugfs framework of VFIO, if the CONFIG_DEBUG_FS 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:
>>
>> data file: used to get the migration data of the live migration device
>> attr file: used to get device attributes of the live migration device
>> debug file: used to test for acquiring and writing device state data
>> for VF device.
>>
>> Signed-off-by: Longfang Liu <liulongfang@huawei.com>
>> ---
>>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    | 290 ++++++++++++++++++
>>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.h    |  11 +
>>  2 files changed, 301 insertions(+)
>>
>> diff --git a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c
>> index a1589947e721..22ebe0e8f90f 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)
>> @@ -606,6 +607,18 @@ 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 *src_migf,
>> +	struct hisi_acc_vf_migration_file *dst_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);
>> @@ -618,12 +631,16 @@ 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->resuming_migf,
>> +						hisi_acc_vdev->debug_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->saving_migf,
>> +						hisi_acc_vdev->debug_migf);
>>  		hisi_acc_vf_disable_fd(hisi_acc_vdev->saving_migf);
>>  		fput(hisi_acc_vdev->saving_migf->filp);
>>  		hisi_acc_vdev->saving_migf = NULL;
>> @@ -1303,6 +1320,273 @@ 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_io(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;
>> +	struct device *dev = vdev->dev;
>> +	u64 data;
>> +	int ret;
>> +
>> +	ret = qm_wait_dev_not_ready(vf_qm);
>> +	if (ret)
>> +		dev_err(dev, "VF device not ready!\n");
>> +
>> +	data = readl(vf_qm->io_base + QM_MB_CMD_SEND_BASE);
>> +	dev_info(dev, "debug mailbox val: 0x%llx\n", data);
>> +
>> +	return ret;
>> +}
>> +
>> +static int hisi_acc_vf_debug_resume(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;
>> +	struct device *dev = vdev->dev;
>> +	int ret;
>> +
>> +	ret = vf_qm_state_save(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		dev_err(dev, "failed to save device data!\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	ret = vf_qm_check_match(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		dev_err(dev, "failed to match the VF!\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	ret = vf_qm_load_data(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		dev_err(dev, "failed to recover the VF!\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	vf_qm_fun_reset(&hisi_acc_vdev->vf_qm);
>> +	dev_info(dev, "successful to resume device data!\n");
>> +
>> +	return 0;
>> +}
>> +
>> +static int hisi_acc_vf_debug_save(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;
>> +	struct device *dev = vdev->dev;
>> +	int ret;
>> +
>> +	ret = vf_qm_state_save(hisi_acc_vdev, migf);
>> +	if (ret) {
>> +		dev_err(dev, "failed to save device data!\n");
>> +		return -EINVAL;
>> +	}
>> +	dev_info(dev, "successful to save device data!\n");
>> +
>> +	return 0;
>> +}
> 
> It seems backwards that we've defined the 'debug' file to be writable
> only in order to select which operation to perform, where the user then
> needs to look in dmesg for information related to an errno.  Wouldn't
> it make more sense to create separate save, restore, and io_test files
> that perform the operation when read and return a buffer indicating the
> error condition or success?  What's the benefit of multiplexing these
> through writes to a single debug file?
>

Although you have added new debug files. But the user's operation is simplified.
Users only need a simple cat operation to trigger the corresponding operation.
And it does not require the user to know the corresponding command.
This option is acceptable

>> +
>> +static int
>> +hisi_acc_vf_debug_operate(struct vfio_device *vdev, unsigned int cmd)
>> +{
>> +	int ret;
>> +
>> +	switch (cmd) {
>> +	case STATE_SAVE:
>> +		ret = hisi_acc_vf_debug_save(vdev);
>> +		if (ret)
>> +			return ret;
>> +		break;
>> +	case STATE_RESUME:
>> +		ret = hisi_acc_vf_debug_resume(vdev);
>> +		if (ret)
>> +			return ret;
>> +		break;
>> +	case RW_IO_TEST:
>> +		ret = hisi_acc_vf_debug_io(vdev);
>> +		if (ret)
>> +			return ret;
>> +		break;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +
>> +	return 0;
>> +}
> 
> Initialize ret = -EINVAL, 'return ret' outside the case, and drop the
> per-case returns.
>

After the above debug file is modified, it will be deleted here.

>> +
>> +static int hisi_acc_vf_debug_check(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;
>> +	enum vfio_device_mig_state state;
>> +
>> +	if (!vdev->mig_ops || !migf) {
>> +		dev_err(vdev->dev, "device not support debugfs!\n");
>> +		return -EINVAL;
>> +	}
> 
> Why did we create the file then?
>
After the above debug file is modified, it will be deleted here.

>> +
>> +	/* If device not opened, the debugfs operation will trigger calltrace */
>> +	(void)vdev->mig_ops->migration_get_state(vdev, &state);
>> +	if (state == VFIO_DEVICE_STATE_ERROR ||
>> +	    state == VFIO_DEVICE_STATE_STOP) {
>> +		dev_err(vdev->dev, "device not opened!\n");
>> +		return -EINVAL;
>> +	}
> 
> And we can't use something like open_count?  What protects this from
> racing against the device being released?
>

There is indeed a need for a more atomic detection method to ensure
that the device can be operated.

>> +
>> +	return 0;
>> +}
>> +
>> +static ssize_t hisi_acc_vf_debug_write(struct file *filp, const char __user *buffer,
>> +			    size_t count, loff_t *pos)
>> +{
>> +	struct vfio_device	*vdev = filp->private_data;
>> +	char tbuf[VFIO_DEV_DBG_LEN];
>> +	unsigned long cmd;
>> +	int len, ret;
>> +
>> +	if (*pos)
>> +		return 0;
>> +
>> +	if (count >= VFIO_DEV_DBG_LEN)
>> +		return -ENOSPC;
>> +
>> +	ret = hisi_acc_vf_debug_check(vdev);
>> +	if (ret)
>> +		return -EINVAL;
>> +
>> +	len = simple_write_to_buffer(tbuf, VFIO_DEV_DBG_LEN - 1,
>> +					pos, buffer, count);
>> +	if (len < 0 || len > VFIO_DEV_DBG_LEN - 1)
>> +		return -EINVAL;
>> +	tbuf[len] = '\0';
>> +	if (kstrtoul(tbuf, 0, &cmd))
>> +		return -EFAULT;
>> +
>> +	ret = hisi_acc_vf_debug_operate(vdev, cmd);
>> +	if (ret) {
>> +		dev_err(vdev->dev, "device debug test failed!\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	return count;
>> +}
>> +
>> +static const struct file_operations hisi_acc_vf_debug_fops = {
>> +	.owner = THIS_MODULE,
>> +	.open = simple_open,
>> +	.write = hisi_acc_vf_debug_write,
>> +};
>> +
>> +static void seq_print_hex_data(struct seq_file *seq, const void *buf, size_t len)
>> +{
>> +#define HEX_LINE_SIZE		131
>> +#define HEX_ROW_SIZE		16
>> +	unsigned char linebuf[HEX_LINE_SIZE];
>> +	int i, linelen, remaining = len;
>> +	const u8 *ptr = buf;
>> +
>> +	for (i = 0; i < len; i += HEX_ROW_SIZE) {
>> +		linelen = min(remaining, HEX_ROW_SIZE);
>> +		remaining -= HEX_ROW_SIZE;
>> +
>> +		hex_dump_to_buffer(ptr + i, linelen, HEX_ROW_SIZE, 1,
>> +					linebuf, sizeof(linebuf), false);
>> +
>> +		seq_printf(seq, "%s%.8x: %s\n", "Mig Data:", i, linebuf);
>> +	}
>> +}
> 
> Can't this use seq_hex_dump()?  If there's a _good_ reason why not, it
> should be noted in comments and the function should be renamed not to
> pollute the seq_ namespace.  Thanks,
> 

I'll debug it with seq_hex_dump().

Thanks,
Longfang.
> Alex
> 
>> +
>> +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_print_hex_data(seq, (unsigned char *)&debug_migf->vf_data,
>> +				vf_data_sz);
>> +	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;
>> +
>> +	vfio_device_debugfs_init(vdev);
>> +
>> +	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) {
>> +		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_file("debug", 0200, vfio_hisi_acc,
>> +				  vdev, &hisi_acc_vf_debug_fops);
>> +
>> +	return 0;
>> +}
>> +
>> +static void hisi_acc_vf_debugfs_exit(struct hisi_acc_vf_core_device *hisi_acc_vdev)
>> +{
>> +	struct vfio_device *vdev = &hisi_acc_vdev->core_device.vdev;
>> +
>> +	if (!debugfs_initialized())
>> +		return;
>> +
>> +	vfio_device_debugfs_exit(vdev);
>> +	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);
>> @@ -1416,6 +1700,9 @@ static int hisi_acc_vfio_pci_probe(struct pci_dev *pdev, const struct pci_device
>>  	if (IS_ERR(hisi_acc_vdev))
>>  		return PTR_ERR(hisi_acc_vdev);
>>  
>> +	if (ops == &hisi_acc_vfio_pci_migrn_ops)
>> +		hisi_acc_vfio_debug_init(hisi_acc_vdev);
>> +
>>  	dev_set_drvdata(&pdev->dev, &hisi_acc_vdev->core_device);
>>  	ret = vfio_pci_core_register_device(&hisi_acc_vdev->core_device);
>>  	if (ret)
>> @@ -1423,6 +1710,8 @@ static int hisi_acc_vfio_pci_probe(struct pci_dev *pdev, const struct pci_device
>>  	return 0;
>>  
>>  out_put_vdev:
>> +	if (ops == &hisi_acc_vfio_pci_migrn_ops)
>> +		hisi_acc_vf_debugfs_exit(hisi_acc_vdev);
>>  	vfio_put_device(&hisi_acc_vdev->core_device.vdev);
>>  	return ret;
>>  }
>> @@ -1431,6 +1720,7 @@ static void hisi_acc_vfio_pci_remove(struct pci_dev *pdev)
>>  {
>>  	struct hisi_acc_vf_core_device *hisi_acc_vdev = hisi_acc_drvdata(pdev);
>>  
>> +	hisi_acc_vf_debugfs_exit(hisi_acc_vdev);
>>  	vfio_pci_core_unregister_device(&hisi_acc_vdev->core_device);
>>  	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 dcabfeec6ca1..ef50b12f018d 100644
>> --- a/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
>> +++ b/drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.h
>> @@ -49,6 +49,14 @@
>>  #define QM_EQC_DW0		0X8000
>>  #define QM_AEQC_DW0		0X8020
>>  
>> +#define VFIO_DEV_DBG_LEN		256
>> +
>> +enum mig_debug_cmd {
>> +	STATE_SAVE,
>> +	STATE_RESUME,
>> +	RW_IO_TEST,
>> +};
>> +
>>  struct acc_vf_data {
>>  #define QM_MATCH_SIZE offsetofend(struct acc_vf_data, qm_rsv_state)
>>  	/* QM match information */
>> @@ -113,5 +121,8 @@ 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;
>> +
>> +	/* For debugfs */
>> +	struct hisi_acc_vf_migration_file *debug_migf;
>>  };
>>  #endif /* HISI_ACC_VFIO_PCI_H */
> 
> .
>