linux-kernel - Re: [PATCH v2 4/5] HID: hv: Remove dependencies on PAGE

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Message-ID: <87h88vdr36.fsf@vitty.brq.redhat.com>
Date:   Wed, 12 Jun 2019 12:40:29 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Maya Nakamura <m.maya.nakamura@...il.com>
Cc:     x86@...nel.org, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, mikelley@...rosoft.com,
        kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        sashal@...nel.org
Subject: Re: [PATCH v2 4/5] HID: hv: Remove dependencies on PAGE_SIZE for ring buffer

Maya Nakamura <m.maya.nakamura@...il.com> writes:

> Define the ring buffer size as a constant expression because it should
> not depend on the guest page size.
>
> Signed-off-by: Maya Nakamura <m.maya.nakamura@...il.com>
> ---
>  drivers/hid/hid-hyperv.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/hid/hid-hyperv.c b/drivers/hid/hid-hyperv.c
> index d3311d714d35..e8b154fa38e2 100644
> --- a/drivers/hid/hid-hyperv.c
> +++ b/drivers/hid/hid-hyperv.c
> @@ -112,8 +112,8 @@ struct synthhid_input_report {
>  
>  #pragma pack(pop)
>  
> -#define INPUTVSC_SEND_RING_BUFFER_SIZE		(10*PAGE_SIZE)
> -#define INPUTVSC_RECV_RING_BUFFER_SIZE		(10*PAGE_SIZE)
> +#define INPUTVSC_SEND_RING_BUFFER_SIZE		(40 * 1024)
> +#define INPUTVSC_RECV_RING_BUFFER_SIZE		(40 * 1024)
>  

My understanding is that this size is pretty arbitrary and as I see you
use it for hyperv-keyboard.c as well. It may make sense to have a
define, something like HYPERV_STD_RINGBUFFER_SIZE.

>  
>  enum pipe_prot_msg_type {

-- 
Vitaly