RE: [PATCH v3 2/3] drivers: hv: vmbus: add test attributes to debugfs

From: Michael Kelley
Date: Wed Aug 21 2019 - 19:11:00 EST


From: Branden Bonaby <brandonbonaby94@xxxxxxxxx> Sent: Tuesday, August 20, 2019 4:39 PM
>
> Expose the test parameters as part of the debugfs channel attributes.
> We will control the testing state via these attributes.
>
> Signed-off-by: Branden Bonaby <brandonbonaby94@xxxxxxxxx>
> ---
> Changes in v3:
> - Change call to IS_ERR_OR_NULL, to IS_ERR.
>
> Changes in v2:
> - Move test attributes to debugfs.
> - Wrap test code under #ifdef statements.
> - Add new documentation file under Documentation/ABI/testing.
> - Make commit message reflect the change from from sysfs to debugfs.
>
> Documentation/ABI/testing/debugfs-hyperv | 21 +++
> MAINTAINERS | 1 +
> drivers/hv/vmbus_drv.c | 167 +++++++++++++++++++++++
> 3 files changed, 189 insertions(+)
> create mode 100644 Documentation/ABI/testing/debugfs-hyperv
>
> diff --git a/Documentation/ABI/testing/debugfs-hyperv
> b/Documentation/ABI/testing/debugfs-hyperv
> new file mode 100644
> index 000000000000..b25f751fafa8
> --- /dev/null
> +++ b/Documentation/ABI/testing/debugfs-hyperv
> @@ -0,0 +1,21 @@
> +What: /sys/kernel/debug/hyperv/<UUID>/fuzz_test_state
> +Date: August 2019
> +KernelVersion: 5.3
> +Contact: Branden Bonaby <brandonbonaby94@xxxxxxxxx>
> +Description: Fuzz testing status of a vmbus device, whether its in an ON
> + state or a OFF state

Document what values are actually returned?

> +Users: Debugging tools
> +
> +What: /sys/kernel/debug/hyperv/<UUID>/delay/fuzz_test_buffer_interrupt_delay
> +Date: August 2019
> +KernelVersion: 5.3
> +Contact: Branden Bonaby <brandonbonaby94@xxxxxxxxx>
> +Description: Fuzz testing buffer delay value between 0 - 1000

It would be helpful to document the units -- I think this is 0 to 1000
microseconds.

> +Users: Debugging tools
> +
> +What: /sys/kernel/debug/hyperv/<UUID>/delay/fuzz_test_message_delay
> +Date: August 2019
> +KernelVersion: 5.3
> +Contact: Branden Bonaby <brandonbonaby94@xxxxxxxxx>
> +Description: Fuzz testing message delay value between 0 - 1000

Same here.

> +Users: Debugging tools
> diff --git a/MAINTAINERS b/MAINTAINERS
> index e81e60bd7c26..120284a8185f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -7460,6 +7460,7 @@ F: include/uapi/linux/hyperv.h
> F: include/asm-generic/mshyperv.h
> F: tools/hv/
> F: Documentation/ABI/stable/sysfs-bus-vmbus
> +F: Documentation/ABI/testing/debugfs-hyperv
>
> HYPERBUS SUPPORT
> M: Vignesh Raghavendra <vigneshr@xxxxxx>
> diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
> index ebd35fc35290..d2e47f04d172 100644
> --- a/drivers/hv/vmbus_drv.c
> +++ b/drivers/hv/vmbus_drv.c
> @@ -919,6 +919,10 @@ static void vmbus_device_release(struct device *device)
> struct hv_device *hv_dev = device_to_hv_device(device);
> struct vmbus_channel *channel = hv_dev->channel;
>
> +#ifdef CONFIG_HYPERV_TESTING
> + hv_debug_rm_dev_dir(hv_dev);
> +#endif /* CONFIG_HYPERV_TESTING */

Same comment in as previous patch about #ifdef inline in the code,
and similarly for other occurrences in this patch.

> +
> mutex_lock(&vmbus_connection.channel_mutex);
> hv_process_channel_removal(channel);
> mutex_unlock(&vmbus_connection.channel_mutex);
> @@ -1727,6 +1731,9 @@ int vmbus_device_register(struct hv_device *child_device_obj)
> pr_err("Unable to register primary channeln");
> goto err_kset_unregister;
> }
> +#ifdef CONFIG_HYPERV_TESTING
> + hv_debug_add_dev_dir(child_device_obj);
> +#endif /* CONFIG_HYPERV_TESTING */
>
> return 0;
>
> @@ -2086,6 +2093,159 @@ static void hv_crash_handler(struct pt_regs *regs)
> hyperv_cleanup();
> };
>
> +#ifdef CONFIG_HYPERV_TESTING
> +
> +struct dentry *hv_root;
> +
> +static int hv_debugfs_delay_get(void *data, u64 *val)
> +{
> + *val = *(u32 *)data;
> + return 0;
> +}
> +
> +static int hv_debugfs_delay_set(void *data, u64 val)
> +{
> + if (val >= 1 && val <= 1000)
> + *(u32 *)data = val;
> + /*Best to not use else statement here since we want
> + * the delay to remain the same if val > 1000
> + */

The standard multi-line comment style would be:

/*
* Best to not use else statement here since we want
* the delay to remain the same if val > 1000
*/

> + else if (val <= 0)
> + *(u32 *)data = 0;

You could consider returning an error for an invalid
value (< 0, or > 1000).

> + return 0;
> +}
> +
> +DEFINE_DEBUGFS_ATTRIBUTE(hv_debugfs_delay_fops, hv_debugfs_delay_get,
> + hv_debugfs_delay_set, "%llu\n");
> +

Michael