linux-kernel - RE: [EXT] Re: [net PATCH] octeontx2-pf: Use GFP

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Date:   Tue, 10 Jan 2023 08:55:50 +0000
From:   Geethasowjanya Akula <gakula@...vell.com>
To:     Eric Dumazet <edumazet@...gle.com>
CC:     Leon Romanovsky <leon@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Subbaraya Sundeep Bhatta <sbhatta@...vell.com>,
        Hariprasad Kelam <hkelam@...vell.com>,
        Sunil Kovvuri Goutham <sgoutham@...vell.com>
Subject: RE: [EXT] Re: [net PATCH] octeontx2-pf: Use GFP_ATOMIC in atomic
 context



-----Original Message-----
From: Eric Dumazet <edumazet@...gle.com> 
Sent: Tuesday, January 10, 2023 2:05 PM
To: Geethasowjanya Akula <gakula@...vell.com>
Cc: Leon Romanovsky <leon@...nel.org>; netdev@...r.kernel.org; linux-kernel@...r.kernel.org; kuba@...nel.org; pabeni@...hat.com; davem@...emloft.net; Subbaraya Sundeep Bhatta <sbhatta@...vell.com>; Hariprasad Kelam <hkelam@...vell.com>; Sunil Kovvuri Goutham <sgoutham@...vell.com>
Subject: [EXT] Re: [net PATCH] octeontx2-pf: Use GFP_ATOMIC in atomic context

External Email

----------------------------------------------------------------------
On Tue, Jan 10, 2023 at 8:54 AM Geethasowjanya Akula <gakula@...vell.com> wrote:
>>
>>
>>
>> -----Original Message-----
>> From: Leon Romanovsky <leon@...nel.org>
>> Sent: Sunday, January 8, 2023 6:39 PM
>> To: Geethasowjanya Akula <gakula@...vell.com>
>> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; 
>> kuba@...nel.org; pabeni@...hat.com; davem@...emloft.net; 
>> edumazet@...gle.com; Subbaraya Sundeep Bhatta <sbhatta@...vell.com>; 
>> Hariprasad Kelam <hkelam@...vell.com>; Sunil Kovvuri Goutham 
>> <sgoutham@...vell.com>
>> Subject: [EXT] Re: [net PATCH] octeontx2-pf: Use GFP_ATOMIC in atomic 
>> context
>>
>> External Email
>>
>> ----------------------------------------------------------------------
>> On Sat, Jan 07, 2023 at 10:11:39AM +0530, Geetha sowjanya wrote:
>> >> Use GFP_ATOMIC flag instead of GFP_KERNEL while allocating memory 
>> >> in atomic context.
>>
>> >Awesome, but the changed functions don't run in atomic context.
>>
>> drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
>>     1368         /* Flush accumulated messages */
>>     1369         err = otx2_sync_mbox_msg(&pfvf->mbox);
>>     1370         if (err)
>>     1371                 goto fail;
>>     1372
>>     1373         get_cpu();
>>                  ^^^^^^^^^
>> The get_cpu() disables preemption.

>Forcing GFP_ATOMIC in init functions is not desirable.
>
>Please move around the get_cpu() so that we keep GFP_KERNEL whenever possible.
Ok will submit v2 with suggested changes.
>
>diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
>b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
>index 88f8772a61cd527c2ab138fb5a996470a7dfd456..2e628e12cd1ff92756f054639abd777ea185680f
>100644
>--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
>+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
>@@ -1370,7 +1370,6 @@ int otx2_sq_aura_pool_init(struct otx2_nic *pfvf)
>       if (err)
>                goto fail;
>
>-       get_cpu();
>        /* Allocate pointers and free them to aura/pool */
>       for (qidx = 0; qidx < hw->tot_tx_queues; qidx++) {
>                pool_id = otx2_get_pool_idx(pfvf, AURA_NIX_SQ, qidx); @@ -1388,13 +1387,17 @@ int otx2_sq_aura_pool_init(struct otx2_nic *pfvf)
>                        err = otx2_alloc_rbuf(pfvf, pool, &bufptr);
>                        if (err)
>                                goto err_mem;
>+                       /* __cn10k_aura_freeptr() needs to be called
>+                        * with preemption disabled.
>+                        */
>+                       get_cpu();
>                        pfvf->hw_ops->aura_freeptr(pfvf, pool_id, bufptr);
>+                       put_cpu();
>                        sq->sqb_ptrs[sq->sqb_count++] = (u64)bufptr;
>               }
>        }
>
> err_mem:
>-       put_cpu();
>        return err ? -ENOMEM : 0;
>
> fail: