RE: [PATCH v4 08/11] Input: hyperv-keyboard: Use VMBUS_RING_SIZE() for ringbuffer sizes

[Michael Kelley]

From: Boqun Feng <boqun.feng@xxxxxxxxx> 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@xxxxxxxxx>
> Cc: Michael Kelley <mikelley@xxxxxxxxxxxxx>
> Cc: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> ---
> Michael and Dmitry,
> 
> I change the code because of a problem I found:
> 
> 	https://lore.kernel.org/lkml/20200914084600.GA45838@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> 
> , so I drop your Reviewed-by or Acked-by tag. If the update version
> looks good to you, may I add your tag again? Thanks in advance, and
> apologies for the inconvenience.
> 
> Regards,
> Boqun
> 
>  drivers/input/serio/hyperv-keyboard.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/input/serio/hyperv-keyboard.c b/drivers/input/serio/hyperv-keyboard.c
> index df4e9f6f4529..1a7b72a9016d 100644
> --- a/drivers/input/serio/hyperv-keyboard.c
> +++ b/drivers/input/serio/hyperv-keyboard.c
> @@ -75,8 +75,8 @@ struct synth_kbd_keystroke {
> 
>  #define HK_MAXIMUM_MESSAGE_SIZE 256
> 
> -#define KBD_VSC_SEND_RING_BUFFER_SIZE		(40 * 1024)
> -#define KBD_VSC_RECV_RING_BUFFER_SIZE		(40 * 1024)
> +#define KBD_VSC_SEND_RING_BUFFER_SIZE	VMBUS_RING_SIZE(36 * 1024)
> +#define KBD_VSC_RECV_RING_BUFFER_SIZE	VMBUS_RING_SIZE(36 * 1024)
> 
>  #define XTKBD_EMUL0     0xe0
>  #define XTKBD_EMUL1     0xe1
> --
> 2.28.0

Reviewed-by:  Michael Kelley <mikelley@xxxxxxxxxxxxx>