RE: [PATCH v4 10/11] Driver: hv: util: Use VMBUS_RING_SIZE() for ringbuffer sizes

[Michael Kelley <mikelley@microsoft.com>]

From: Boqun Feng <boqun.feng@gmail.com> Sent: Tuesday, September 15, 2020 8:48 PM
> 
> For a Hyper-V vmbus, the size of the ringbuffer has two requirements:
> 
> 1)	it has to take one PAGE_SIZE for the header
> 
> 2)	it has to be PAGE_SIZE aligned so that double-mapping can work
> 
> VMBUS_RING_SIZE() could calculate a correct ringbuffer size which
> fulfills both requirements, therefore use it to make sure vmbus work
> when PAGE_SIZE != HV_HYP_PAGE_SIZE (4K).
> 
> Note that since the argument for VMBUS_RING_SIZE() is the size of
> payload (data part), so it will be minus 4k (the size of header when
> PAGE_SIZE = 4k) than the original value to keep the ringbuffer total
> size unchanged when PAGE_SIZE = 4k.
> 
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
> Cc: Michael Kelley <mikelley@microsoft.com>
> 
> ---
> Michael,
> 
> I drop your Reviewed-by tag because of the page align issue. Could you
> review this updated version? Thanks!
> 
> Regards,
> Boqun
> 
> 
>  drivers/hv/hv_util.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
> index a4e8d96513c2..05566ecdbe4b 100644
> --- a/drivers/hv/hv_util.c
> +++ b/drivers/hv/hv_util.c
> @@ -500,6 +500,9 @@ static void heartbeat_onchannelcallback(void *context)
>  	}
>  }
> 
> +#define HV_UTIL_RING_SEND_SIZE VMBUS_RING_SIZE(3 * HV_HYP_PAGE_SIZE)
> +#define HV_UTIL_RING_RECV_SIZE VMBUS_RING_SIZE(3 * HV_HYP_PAGE_SIZE)
> +
>  static int util_probe(struct hv_device *dev,
>  			const struct hv_vmbus_device_id *dev_id)
>  {
> @@ -530,8 +533,8 @@ static int util_probe(struct hv_device *dev,
> 
>  	hv_set_drvdata(dev, srv);
> 
> -	ret = vmbus_open(dev->channel, 4 * HV_HYP_PAGE_SIZE,
> -			 4 * HV_HYP_PAGE_SIZE, NULL, 0, srv->util_cb,
> +	ret = vmbus_open(dev->channel, HV_UTIL_RING_SEND_SIZE,
> +			 HV_UTIL_RING_RECV_SIZE, NULL, 0, srv->util_cb,
>  			 dev->channel);
>  	if (ret)
>  		goto error;
> @@ -590,8 +593,8 @@ static int util_resume(struct hv_device *dev)
>  			return ret;
>  	}
> 
> -	ret = vmbus_open(dev->channel, 4 * HV_HYP_PAGE_SIZE,
> -			 4 * HV_HYP_PAGE_SIZE, NULL, 0, srv->util_cb,
> +	ret = vmbus_open(dev->channel, HV_UTIL_RING_SEND_SIZE,
> +			 HV_UTIL_RING_RECV_SIZE, NULL, 0, srv->util_cb,
>  			 dev->channel);
>  	return ret;
>  }
> --
> 2.28.0

Reviewed-by:  Michael Kelley <mikelley@microsoft.com>