linux-kernel - RE: [PATCH v2 net] net: mana: Fix doorbell out of order violation and avoid unnecessary doorbell rings

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Message-ID:
 <DM4PR21MB35364264950F0182B50F5846CEBA2@DM4PR21MB3536.namprd21.prod.outlook.com>
Date: Fri, 9 Aug 2024 15:19:25 +0000
From: Long Li <longli@...rosoft.com>
To: Simon Horman <horms@...nel.org>
CC: KY Srinivasan <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>, "David S.
 Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub
 Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Shradha Gupta
	<shradhagupta@...ux.microsoft.com>, Konstantin Taranov
	<kotaranov@...rosoft.com>, Souradeep Chakrabarti
	<schakrabarti@...ux.microsoft.com>, Erick Archer <erick.archer@...look.com>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: RE: [PATCH v2 net] net: mana: Fix doorbell out of order violation and
 avoid unnecessary doorbell rings

> Subject: Re: [PATCH v2 net] net: mana: Fix doorbell out of order violation and
> avoid unnecessary doorbell rings
> 
> On Wed, Aug 07, 2024 at 04:17:06PM -0700, longli@...uxonhyperv.com
> wrote:
> > From: Long Li <longli@...rosoft.com>
> >
> > After napi_complete_done() is called when NAPI is polling in the
> > current process context, another NAPI may be scheduled and start
> > running in softirq on another CPU and may ring the doorbell before the
> > current CPU does. When combined with unnecessary rings when there is
> > no need to arm the CQ, it triggers error paths in the hardware.
> >
> > This patch fixes this by calling napi_complete_done() after doorbell
> > rings. It limits the number of unnecessary rings when there is no need
> > to arm. MANA hardware specifies that there must be one doorbell ring
> > every 8 CQ wraparounds. This driver guarantees one doorbell ring as
> > soon as the number of consumed CQEs exceeds 4 CQ wraparounds. In
> > pratical
> 
> nit: practical
> 
>      Flagged by checkpatch.pl --codespell
> 
> ...

Thank you! Will fix it.