netdev - Re: [RFC PATCH V4 12/13] netfront: multi page ring support.

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Date:	Thu, 16 Feb 2012 10:02:51 +0000
From:	Wei Liu <wei.liu2@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	<wei.liu2@...rix.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"Ian Campbell" <Ian.Campbell@...rix.com>
Subject: Re: [RFC PATCH V4 12/13] netfront: multi page ring support.

On Wed, 2012-02-15 at 22:42 +0000, Konrad Rzeszutek Wilk wrote:
> On Thu, Feb 02, 2012 at 04:49:22PM +0000, Wei Liu wrote:
> > 
> > Signed-off-by: Wei Liu <wei.liu2@...rix.com>
> 
> It also needs this:
> 
> From 4cf97c025792cf073edc4d312b962ecc0b3b67ab Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> Date: Wed, 15 Feb 2012 17:39:46 -0500
> Subject: [PATCH] xen/net: Don't try to use all of the rings if we are not
>  built for it.
> 
> Otherwise we end up:
> 
> BUG: unable to handle kernel paging request at ffff88004000c0c8
> IP: [<ffffffff810f1ee4>] free_one_page+0x144/0x410
> PGD 1806063 PUD 0
> 22:22:34 tst007 logger: /etc/xen/scripts/vif-bridge: offline XENBUS_PATH=backend/vif/1/0
> 00 [#1] SMP
> CPU 0
> Modules linked in:
> 
> Pid: 17, comm: xenwatch Not tainted 3.2.0upstream #2 Xen HVM domU
> RIP: 0010:[<ffffffff810f1ee4>]  [<ffffffff810f1ee4>] free_one_page+0x144/0x410
> RSP: 0018:ffff88003bea3c40  EFLAGS: 00010046
> .. snip.
> Call Trace:
>  [<ffffffff810f2c7f>] __free_pages_ok+0x9f/0xe0
>  [<ffffffff810f4eab>] __free_pages+0x1b/0x40
>  [<ffffffff810f4f1a>] free_pages+0x4a/0x60
>  [<ffffffff8138b33d>] xennet_disconnect_backend+0xbd/0x130
>  [<ffffffff8138bd88>] talk_to_netback+0x8e8/0x1160
>  [<ffffffff812f4e28>] ? xenbus_gather+0xd8/0x170
>  [<ffffffff8138e3bd>] netback_changed+0xcd/0x550
>  [<ffffffff812f5bb8>] xenbus_otherend_changed+0xa8/0xb0
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  drivers/net/xen-netfront.c |   14 +++++++++++++-
>  1 files changed, 13 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
> index 0223552..1eadd90 100644
> --- a/drivers/net/xen-netfront.c
> +++ b/drivers/net/xen-netfront.c
> @@ -29,6 +29,8 @@
>   * IN THE SOFTWARE.
>   */
>  
> +#define DEBUG 1
> +
>  #include <linux/module.h>
>  #include <linux/kernel.h>
>  #include <linux/netdevice.h>
> @@ -66,7 +68,7 @@ struct netfront_cb {
>  
>  #define GRANT_INVALID_REF	0
>  
> -#define XENNET_MAX_RING_PAGE_ORDER 2
> +#define XENNET_MAX_RING_PAGE_ORDER 4

I guess this is you tuning with page order? And here is not the only one
place you changed?

As a matter of fact, in the previous patch 8 I encode hard limit 2 on
the ring page order, your change here will stop FE / BE from connecting.

I think I will also need to change this to something like

  #define XENNET_MAX_RING_PAGE_ORDER XENBUS_MAX_RING_PAGE_ORDER

to remind people to modify that value. 

>  #define XENNET_MAX_RING_PAGES      (1U << XENNET_MAX_RING_PAGE_ORDER)
>  
>  #define NET_TX_RING_SIZE(_nr_pages)					\
> @@ -1611,6 +1613,11 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
>  		info->tx_ring_page_order = 0;
>  		dev_info(&dev->dev, "single tx ring\n");
>  	} else {
> +		if (max_tx_ring_page_order > XENNET_MAX_RING_PAGE_ORDER) {
> +			dev_warn(&dev->dev, "Backend can do %d pages but we can only do %d!\n",
> +				max_tx_ring_page_order, XENNET_MAX_RING_PAGE_ORDER);
> +			max_tx_ring_page_order = XENNET_MAX_RING_PAGE_ORDER;
> +		}
>  		info->tx_ring_page_order = max_tx_ring_page_order;
>  		dev_info(&dev->dev, "multi page tx ring, order = %d\n",
>  			 max_tx_ring_page_order);
> @@ -1642,6 +1649,11 @@ static int setup_netfront(struct xenbus_device *dev, struct netfront_info *info)
>  		dev_info(&dev->dev, "single rx ring\n");
>  	} else {
>  		info->rx_ring_page_order = max_rx_ring_page_order;
> +		if (max_rx_ring_page_order > XENNET_MAX_RING_PAGE_ORDER) {
> +			dev_warn(&dev->dev, "Backend can do %d pages but we can only do %d!\n",
> +				max_rx_ring_page_order, XENNET_MAX_RING_PAGE_ORDER);
> +			max_rx_ring_page_order = XENNET_MAX_RING_PAGE_ORDER;
> +		}
>  		dev_info(&dev->dev, "multi page rx ring, order = %d\n",
>  			 max_rx_ring_page_order);
>  	}

Thanks for this, I will squash it into my patch.


Wei.

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