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Message-ID: <ff787286-e3f6-1a32-2eb0-3d7976aeb34e@huawei.com>
Date: Mon, 29 Jan 2024 10:24:00 +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 2/3] hisi_acc_vfio_pci: register debugfs for hisilicon
migration driver
On 2024/1/26 6:38, Alex Williamson wrote:
> On Thu, 25 Jan 2024 16:10:30 +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
>> | +--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@...wei.com>
>> ---
>> .../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 */
>
> .
>
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