Messages in this thread | | | Date | Thu, 19 Oct 2023 10:30:53 +0200 | Subject | Re: [PATCH v17 1/2] vfio/migration: Add debugfs to live migration driver | From | Cédric Le Goater <> |
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On 10/19/23 10:03, liulongfang wrote: > On 2023/10/16 23:17, Cédric Le Goater wrote: >> Hello Longfang, >> >> On 10/13/23 11:04, Longfang Liu wrote: >>> There are multiple devices, software and operational steps involved >>> in the process of live migration. An error occurred on any node may >>> cause the live migration operation to fail. >>> This complex process makes it very difficult to locate and analyze >>> the cause when the function fails. >>> >>> In order to quickly locate the cause of the problem when the >>> live migration fails, I added a set of debugfs to the vfio >>> live migration driver. >>> >>> +-------------------------------------------+ >>> | | >>> | | >>> | QEMU | >>> | | >>> | | >>> +---+----------------------------+----------+ >>> | ^ | ^ >>> | | | | >>> | | | | >>> v | v | >>> +---------+--+ +---------+--+ >>> |src vfio_dev| |dst vfio_dev| >>> +--+---------+ +--+---------+ >>> | ^ | ^ >>> | | | | >>> v | | | >>> +-----------+----+ +-----------+----+ >>> |src dev debugfs | |dst dev debugfs | >>> +----------------+ +----------------+ >>> >>> The entire debugfs directory will be based on the definition of >>> the CONFIG_DEBUG_FS macro. If this macro is not enabled, the >>> interfaces in vfio.h will be empty definitions, and the creation >>> and initialization of the debugfs directory will not be executed. >>> >>> vfio >>> | >>> +---<dev_name1> >>> | +---migration >>> | +--state >>> | >>> +---<dev_name2> >>> +---migration >>> +--state >>> >>> debugfs will create a public root directory "vfio" file. >>> then create a dev_name() file for each live migration device. >>> First, create a unified state acquisition file of "migration" >>> in this device directory. >>> Then, create a public live migration state lookup file "state". >>> >>> Signed-off-by: Longfang Liu <liulongfang@huawei.com> >>> --- >>> drivers/vfio/Kconfig | 10 +++++ >>> drivers/vfio/Makefile | 1 + >>> drivers/vfio/debugfs.c | 90 +++++++++++++++++++++++++++++++++++++++ >>> drivers/vfio/vfio.h | 14 ++++++ >>> drivers/vfio/vfio_main.c | 14 +++++- >>> include/linux/vfio.h | 7 +++ >>> include/uapi/linux/vfio.h | 1 + >>> 7 files changed, 135 insertions(+), 2 deletions(-) >>> create mode 100644 drivers/vfio/debugfs.c >>> >>> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig >>> index 6bda6dbb4878..ceae52fd7586 100644 >>> --- a/drivers/vfio/Kconfig >>> +++ b/drivers/vfio/Kconfig >>> @@ -80,6 +80,16 @@ config VFIO_VIRQFD >>> select EVENTFD >>> default n >>> +config VFIO_DEBUGFS >>> + bool "Export VFIO internals in DebugFS" >>> + depends on DEBUG_FS >>> + help >>> + Allows exposure of VFIO device internals. This option enables >>> + the use of debugfs by VFIO drivers as required. The device can >>> + cause the VFIO code create a top-level debug/vfio directory >>> + during initialization, and then populate a subdirectory with >>> + entries as required. >>> + >>> source "drivers/vfio/pci/Kconfig" >>> source "drivers/vfio/platform/Kconfig" >>> source "drivers/vfio/mdev/Kconfig" >>> diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile >>> index c82ea032d352..d43a699d55b1 100644 >>> --- a/drivers/vfio/Makefile >>> +++ b/drivers/vfio/Makefile >>> @@ -8,6 +8,7 @@ vfio-$(CONFIG_VFIO_GROUP) += group.o >>> vfio-$(CONFIG_IOMMUFD) += iommufd.o >>> vfio-$(CONFIG_VFIO_CONTAINER) += container.o >>> vfio-$(CONFIG_VFIO_VIRQFD) += virqfd.o >>> +vfio-$(CONFIG_VFIO_DEBUGFS) += debugfs.o >>> obj-$(CONFIG_VFIO_IOMMU_TYPE1) += vfio_iommu_type1.o >>> obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o >>> diff --git a/drivers/vfio/debugfs.c b/drivers/vfio/debugfs.c >>> new file mode 100644 >>> index 000000000000..ae53d6110f47 >>> --- /dev/null >>> +++ b/drivers/vfio/debugfs.c >>> @@ -0,0 +1,90 @@ >>> +// SPDX-License-Identifier: GPL-2.0-only >>> +/* >>> + * Copyright (c) 2023, HiSilicon Ltd. >>> + */ >>> + >>> +#include <linux/device.h> >>> +#include <linux/debugfs.h> >>> +#include <linux/seq_file.h> >>> +#include <linux/vfio.h> >>> +#include "vfio.h" >>> + >>> +static struct dentry *vfio_debugfs_root; >>> + >>> +static int vfio_device_state_read(struct seq_file *seq, void *data) >>> +{ >>> + struct device *vf_dev = seq->private; >>> + struct vfio_device *vdev = container_of(vf_dev, struct vfio_device, device); >>> + enum vfio_device_mig_state state; >>> + int ret; >>> + >>> + BUILD_BUG_ON(VFIO_DEVICE_STATE_NR != >>> + VFIO_DEVICE_STATE_PRE_COPY_P2P + 1); >>> + >>> + ret = vdev->mig_ops->migration_get_state(vdev, &state); >>> + if (ret) >>> + return -EINVAL; >>> + >>> + switch (state) { >>> + case VFIO_DEVICE_STATE_ERROR: >>> + seq_printf(seq, "%s\n", "ERROR"); >>> + break; >>> + case VFIO_DEVICE_STATE_STOP: >>> + seq_printf(seq, "%s\n", "STOP"); >>> + break; >>> + case VFIO_DEVICE_STATE_RUNNING: >>> + seq_printf(seq, "%s\n", "RUNNING"); >>> + break; >>> + case VFIO_DEVICE_STATE_STOP_COPY: >>> + seq_printf(seq, "%s\n", "STOP_COPY"); >>> + break; >>> + case VFIO_DEVICE_STATE_RESUMING: >>> + seq_printf(seq, "%s\n", "RESUMING"); >>> + break; >>> + case VFIO_DEVICE_STATE_RUNNING_P2P: >>> + seq_printf(seq, "%s\n", "RUNNING_P2P"); >>> + break; >>> + case VFIO_DEVICE_STATE_PRE_COPY: >>> + seq_printf(seq, "%s\n", "PRE_COPY"); >>> + break; >>> + case VFIO_DEVICE_STATE_PRE_COPY_P2P: >>> + seq_printf(seq, "%s\n", "PRE_COPY_P2P"); >>> + break; >>> + default: >>> + seq_printf(seq, "%s\n", "Invalid"); >> >> seq_puts() is more appropriate than seq_printf() above. >> > > There is no difference between seq_puts() and seq_printf() here, > no need to modify it.
seq_puts is simply preferred for unformatted output.
>> I would suggest to add an array or some helper, that the VFIO drivers >> could use to debug the migration flow with pr_* primitives. It can be >> done later. >> > > If you want to debug this migration process in the VFIO driver, > you can refer to vdev->mig_ops->migration_get_state() to read the status. > >> >>> + } >>> + >>> + return 0; >>> +} >>> + >>> +void vfio_device_debugfs_init(struct vfio_device *vdev) >>> +{ >>> + struct device *dev = &vdev->device; >>> + >>> + vdev->debug_root = debugfs_create_dir(dev_name(vdev->dev), vfio_debugfs_root); >>> + >>> + if (vdev->mig_ops) { >>> + struct dentry *vfio_dev_migration = NULL; >> >> mig_dir maybe ? >> > > "vfio_dev_migration " will not affect the readability of the code. > >> It would be easier to understand the nature of the variable IMHO. >> >>> + >>> + vfio_dev_migration = debugfs_create_dir("migration", vdev->debug_root); >>> + debugfs_create_devm_seqfile(dev, "state", vfio_dev_migration, >>> + vfio_device_state_read); >>> + } >>> +} >>> + >>> +void vfio_device_debugfs_exit(struct vfio_device *vdev) >>> +{ >>> + debugfs_remove_recursive(vdev->debug_root); >>> +} >>> + >>> +void vfio_debugfs_create_root(void) >>> +{ >>> + vfio_debugfs_root = debugfs_create_dir("vfio", NULL); >>> +} >>> + >>> +void vfio_debugfs_remove_root(void) >>> +{ >>> + debugfs_remove_recursive(vfio_debugfs_root); >>> + vfio_debugfs_root = NULL; >>> +} >>> + >>> diff --git a/drivers/vfio/vfio.h b/drivers/vfio/vfio.h >>> index 307e3f29b527..bde84ad344e5 100644 >>> --- a/drivers/vfio/vfio.h >>> +++ b/drivers/vfio/vfio.h >>> @@ -448,4 +448,18 @@ static inline void vfio_device_put_kvm(struct vfio_device *device) >>> } >>> #endif >>> +#ifdef CONFIG_VFIO_DEBUGFS >>> +void vfio_debugfs_create_root(void); >>> +void vfio_debugfs_remove_root(void); >>> + >>> +void vfio_device_debugfs_init(struct vfio_device *vdev); >>> +void vfio_device_debugfs_exit(struct vfio_device *vdev); >>> +#else >>> +static inline void vfio_debugfs_create_root(void) { } >>> +static inline void vfio_debugfs_remove_root(void) { } >>> + >>> +static inline void vfio_device_debugfs_init(struct vfio_device *vdev) { } >>> +static inline void vfio_device_debugfs_exit(struct vfio_device *vdev) { } >>> +#endif /* CONFIG_VFIO_DEBUGFS */ >>> + >>> #endif >>> diff --git a/drivers/vfio/vfio_main.c b/drivers/vfio/vfio_main.c >>> index e31e1952d7b8..9aec4c22f051 100644 >>> --- a/drivers/vfio/vfio_main.c >>> +++ b/drivers/vfio/vfio_main.c >>> @@ -309,7 +309,6 @@ static int __vfio_register_dev(struct vfio_device *device, >>> /* Refcounting can't start until the driver calls register */ >>> refcount_set(&device->refcount, 1); >>> - >> >> superfluous change. >> > > A blank line here is to separate it from the comment above. > Makes it easier to be read. > >>> vfio_device_group_register(device); >>> return 0; >>> @@ -320,7 +319,15 @@ static int __vfio_register_dev(struct vfio_device *device, >>> int vfio_register_group_dev(struct vfio_device *device) >>> { >>> - return __vfio_register_dev(device, VFIO_IOMMU); >>> + int ret; >>> + >>> + ret = __vfio_register_dev(device, VFIO_IOMMU); >>> + if (ret) >>> + return ret; >>> + >>> + vfio_device_debugfs_init(device); >> >> Can it be called from __vfio_register_dev() instead ? and mdev devices >> would get debugfs support also. >> > > This is for symmetry in function calls. > The need for symmetry was mentioned in the previous review.
yes. But this is also exluding the mdev devices which is a large VFIO family.
Thanks,
C.
> >> Thanks, >> >> C. >> > Thanks, > Longfang. > >>> + >>> + return 0; >>> } >>> EXPORT_SYMBOL_GPL(vfio_register_group_dev); >>> @@ -378,6 +385,7 @@ void vfio_unregister_group_dev(struct vfio_device *device) >>> } >>> } >>> + vfio_device_debugfs_exit(device); >>> /* Balances vfio_device_set_group in register path */ >>> vfio_device_remove_group(device); >>> } >>> @@ -1676,6 +1684,7 @@ static int __init vfio_init(void) >>> if (ret) >>> goto err_alloc_dev_chrdev; >>> + vfio_debugfs_create_root(); >>> pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n"); >>> return 0; >>> @@ -1691,6 +1700,7 @@ static int __init vfio_init(void) >>> static void __exit vfio_cleanup(void) >>> { >>> + vfio_debugfs_remove_root(); >>> ida_destroy(&vfio.device_ida); >>> vfio_cdev_cleanup(); >>> class_destroy(vfio.device_class); >>> diff --git a/include/linux/vfio.h b/include/linux/vfio.h >>> index 454e9295970c..769d7af86225 100644 >>> --- a/include/linux/vfio.h >>> +++ b/include/linux/vfio.h >>> @@ -69,6 +69,13 @@ struct vfio_device { >>> u8 iommufd_attached:1; >>> #endif >>> u8 cdev_opened:1; >>> +#ifdef CONFIG_DEBUG_FS >>> + /* >>> + * debug_root is a static property of the vfio_device >>> + * which must be set prior to registering the vfio_device. >>> + */ >>> + struct dentry *debug_root; >>> +#endif >>> }; >>> /** >>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h >>> index 7f5fb010226d..2b68e6cdf190 100644 >>> --- a/include/uapi/linux/vfio.h >>> +++ b/include/uapi/linux/vfio.h >>> @@ -1219,6 +1219,7 @@ enum vfio_device_mig_state { >>> VFIO_DEVICE_STATE_RUNNING_P2P = 5, >>> VFIO_DEVICE_STATE_PRE_COPY = 6, >>> VFIO_DEVICE_STATE_PRE_COPY_P2P = 7, >>> + VFIO_DEVICE_STATE_NR, >>> }; >>> /** >> >> . >> >
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