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

[Leon Romanovsky <leon@kernel.org>]

On Fri, Mar 31, 2023 at 08:56:59AM +0000, Geethasowjanya Akula wrote:
> 
> 
> >-----Original Message-----
> >From: Leon Romanovsky <leon@kernel.org> 
> >Sent: Thursday, March 30, 2023 12:46 PM
> >To: Geethasowjanya Akula <gakula@marvell.com>
> >Cc: Sai Krishna Gajula <saikrishnag@marvell.com>; davem@davemloft.net; edumazet@google.com; kuba@kernel.org; pabeni@redhat.com; netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Sunil >Kovvuri Goutham <sgoutham@marvell.com>; richardcochran@gmail.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@kernel.org>
> >> >Sent: Thursday, March 30, 2023 11:26 AM
> >> >To: Sai Krishna Gajula <saikrishnag@marvell.com>
> >> >Cc: davem@davemloft.net; edumazet@google.com; kuba@kernel.org; 
> >> >pabeni@redhat.com; netdev@vger.kernel.org; 
> >> >linux-kernel@vger.kernel.org; Sunil Kovvuri Goutham 
> >> ><sgoutham@marvell.com>; >richardcochran@gmail.com; Geethasowjanya 
> >> >Akula <gakula@marvell.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@marvell.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