RE: [PATCH v4 09/11] HID: hyperv: Use VMBUS_RING_SIZE() for ringbuffer sizes

From: Michael Kelley <mikelley@microsoft.com>
To: Boqun Feng <boqun.feng@gmail.com>,
	"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
	"linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Cc: KY Srinivasan <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>, Jiri Kosina <jikos@kernel.org>,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	"will@kernel.org" <will@kernel.org>,
	"ardb@kernel.org" <ardb@kernel.org>,
	"arnd@arndb.de" <arnd@arndb.de>,
	"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
	"Mark.Rutland@arm.com" <Mark.Rutland@arm.com>,
	"maz@kernel.org" <maz@kernel.org>, Jiri Kosina <jkosina@suse.cz>
Subject: RE: [PATCH v4 09/11] HID: hyperv: Use VMBUS_RING_SIZE() for ringbuffer sizes
Date: Sun, 27 Sep 2020 00:11:40 +0000	[thread overview]
Message-ID: <MW2PR2101MB10522AE6C10071E709655BFFD7340@MW2PR2101MB1052.namprd21.prod.outlook.com> (raw)
In-Reply-To: <20200916034817.30282-10-boqun.feng@gmail.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: Jiri Kosina <jkosina@suse.cz>
> Cc: Michael Kelley <mikelley@microsoft.com>
> ---
> Michael and Jiri,
> 
> I change the code because of a problem I found:
> 
> 	https://lore.kernel.org/lkml/20200914084600.GA45838@debian-boqun.qqnc3lrjykvubdpftowmye0fmh.lx.internal.cloudapp.net/
> 
> , 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/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 0b6ee1dee625..978ee2aab2d4 100644
> --- a/drivers/hid/hid-hyperv.c
> +++ b/drivers/hid/hid-hyperv.c
> @@ -104,8 +104,8 @@ struct synthhid_input_report {
> 
>  #pragma pack(pop)
> 
> -#define INPUTVSC_SEND_RING_BUFFER_SIZE		(40 * 1024)
> -#define INPUTVSC_RECV_RING_BUFFER_SIZE		(40 * 1024)
> +#define INPUTVSC_SEND_RING_BUFFER_SIZE	VMBUS_RING_SIZE(36 * 1024)
> +#define INPUTVSC_RECV_RING_BUFFER_SIZE	VMBUS_RING_SIZE(36 * 1024)
> 
> 
>  enum pipe_prot_msg_type {
> --
> 2.28.0

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