Re: [PATCH 1/6] Drivers: hv: vmbus: Add utility function for querying ring size

Greg KH
2024-02-18T07:12:01Z

On Sat, Feb 17, 2024 at 10:03:35AM -0800, Saurabh Sengar wrote:
> Add a function to query for the preferred ring buffer size of VMBus
> device.

That says what you did, but not why you did it.

>
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> ---
> drivers/hv/channel_mgmt.c | 7 +++++--
> drivers/hv/hyperv_vmbus.h | 5 +++++
> include/linux/hyperv.h | 1 +
> 3 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index 2f4d09ce027a..7ea444d72f9f 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -120,7 +120,8 @@ const struct vmbus_device vmbus_devs[] = {
> },
>
> /* File copy */
> - { .dev_type = HV_FCOPY,
> + { .pref_ring_size = 0x4000,
> + .dev_type = HV_FCOPY,
> HV_FCOPY_GUID,
> .perf_device = false,
> .allowed_in_isolated = false,
> @@ -141,11 +142,13 @@ const struct vmbus_device vmbus_devs[] = {
> },
>
> /* Unknown GUID */
> - { .dev_type = HV_UNKNOWN,
> + { .pref_ring_size = 0x11000,
> + .dev_type = HV_UNKNOWN,

Where do these magic numbers for the size come from?

> .perf_device = false,
> .allowed_in_isolated = false,
> },
> };
> +EXPORT_SYMBOL_GPL(vmbus_devs);
>
> static const struct {
> guid_t guid;
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index f6b1e710f805..76ac5185a01a 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -417,6 +417,11 @@ static inline bool hv_is_perf_channel(struct vmbus_channel *channel)
> return vmbus_devs[channel->device_id].perf_device;
> }
>
> +static inline size_t hv_dev_ring_size(struct vmbus_channel *channel)
> +{
> + return vmbus_devs[channel->device_id].pref_ring_size;
> +}
> +
> static inline bool hv_is_allocated_cpu(unsigned int cpu)
> {
> struct vmbus_channel *channel, *sc;
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 2b00faf98017..5951c7bb5712 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -800,6 +800,7 @@ struct vmbus_requestor {
> #define VMBUS_RQST_RESET (U64_MAX - 3)
>
> struct vmbus_device {
> + size_t pref_ring_size;

No documentation for this? What is the size in units of?

thanks,

greg k-h