linux-kernel - Re: [EXT] Re: [net PATCH 1/7] octeontx2-af: Secure APR table update with the lock

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Date:   Mon, 3 Apr 2023 16:08:20 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Geethasowjanya Akula <gakula@...vell.com>
Cc:     Sai Krishna Gajula <saikrishnag@...vell.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Sunil Kovvuri Goutham <sgoutham@...vell.com>,
        "richardcochran@...il.com" <richardcochran@...il.com>
Subject: Re: [EXT] Re: [net PATCH 1/7] octeontx2-af: Secure APR table update
 with the lock

On Fri, Mar 31, 2023 at 08:56:59AM +0000, Geethasowjanya Akula wrote:
> 
> 
> >-----Original Message-----
> >From: Leon Romanovsky <leon@...nel.org> 
> >Sent: Thursday, March 30, 2023 12:46 PM
> >To: Geethasowjanya Akula <gakula@...vell.com>
> >Cc: Sai Krishna Gajula <saikrishnag@...vell.com>; davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org; pabeni@...hat.com; netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Sunil >Kovvuri Goutham <sgoutham@...vell.com>; richardcochran@...il.com
> >Subject: Re: [EXT] Re: [net PATCH 1/7] octeontx2-af: Secure APR table update with the lock
> >
> >On Thu, Mar 30, 2023 at 06:56:54AM +0000, Geethasowjanya Akula wrote:
> >> 
> >> >-----Original Message-----
> >> >From: Leon Romanovsky <leon@...nel.org>
> >> >Sent: Thursday, March 30, 2023 11:26 AM
> >> >To: Sai Krishna Gajula <saikrishnag@...vell.com>
> >> >Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org; 
> >> >pabeni@...hat.com; netdev@...r.kernel.org; 
> >> >linux-kernel@...r.kernel.org; Sunil Kovvuri Goutham 
> >> ><sgoutham@...vell.com>; >richardcochran@...il.com; Geethasowjanya 
> >> >Akula <gakula@...vell.com>
> >> >Subject: [EXT] Re: [net PATCH 1/7] octeontx2-af: Secure APR table 
> >> >update with the lock
> >> 
> >> >External Email
> >> 
> >> >---------------------------------------------------------------------
> >> >- On Wed, Mar 29, 2023 at 10:36:13PM +0530, Sai Krishna wrote:
> >> >> From: Geetha sowjanya <gakula@...vell.com>
> >> >> 
> >> >> APR table contains the lmtst base address of PF/VFs.
> >> >> These entries are updated by the PF/VF during the device probe. Due 
> >> >> to race condition while updating the entries are getting corrupted. 
> >> >> Hence secure the APR table update with the lock.
> >> 
> >> >However, I don't see rsrc_lock in probe path.
> >> >otx2_probe()
> >> >-> cn10k_lmtst_init()
> >> > -> lmt_base/lmstst is updated with and without mbox.lock.
> >> 
> >> >Where did you take rsrc_lock in probe flow?
> >> 
> >> rsrc_lock is initialized in AF driver. PF/VF driver in cn10k_lmtst_init() send a mbox request to AF to update the lmtst table. 
> >> mbox handler in AF takes rsrc_lock to update lmtst table.
> 
> >Can you please present the stack trace of such flow? What are the actual variables/struct rsrc_lock is protecting?
> 
> The lock tries to protect the request and response register at line#73 and line#83 in below function, from getting overwritten when
> Multiple PFs invokes rvu_get_lmtaddr() simultaneously. 
> For example, if PF1 submit the request at line#73 and got permitted before it reads the response at line#80.
> PF2 got scheduled submit the request then the response of PF1 is overwritten by the PF2 response.  
> When PF1 gets reschedule, it reads wrong data.

I see, thanks