linux-kernel - Re: [PATCH] Octeontx2-af: Fix pci_alloc_irq

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Message-ID: <47282962-19bd-48bc-a09b-df957b467097@oracle.com>
Date: Wed, 15 Oct 2025 14:26:40 +0530
From: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
To: Simon Horman <horms@...nel.org>
Cc: Sunil Goutham <sgoutham@...vell.com>, Linu Cherian
 <lcherian@...vell.com>,
        Geetha sowjanya <gakula@...vell.com>, Jerin Jacob <jerinj@...vell.com>,
        hariprasad <hkelam@...vell.com>,
        Subbaraya Sundeep <sbhatta@...vell.com>,
        Andrew Lunn
 <andrew+netdev@...n.ch>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Nithya Mani <nmani@...vell.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        dan.carpenter@...aro.org, kernel-janitors@...r.kernel.org,
        error27@...il.com
Subject: Re: [PATCH] Octeontx2-af: Fix pci_alloc_irq_vectors() return value
 check

Hi Simon,
On 15/10/25 14:06, Simon Horman wrote:
> On Tue, Oct 14, 2025 at 03:50:47PM +0530, Harshit Mogalapalli wrote:
>> Hi,
>>
>> On 14/10/25 15:44, Harshit Mogalapalli wrote:
>>> In cgx_probe() when pci_alloc_irq_vectors() fails the error value will
>>> be negative and that check is sufficient.
>>>
>>> 	err = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_MSIX);
>>>           if (err < 0 || err != nvec) {
>>>           	...
>>> 	}
>>>
>>> Remove the check which compares err with nvec.
>>>
>>> Fixes: 1463f382f58d ("octeontx2-af: Add support for CGX link management")
>>> Suggested-by: Paolo Abeni <pabeni@...hat.com>
>>> Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@...cle.com>
>>> ---
>>> Only compile tested.
>>> ---
>>>    drivers/net/ethernet/marvell/octeontx2/af/cgx.c | 2 +-
>>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
>>> index d374a4454836..f4d5a3c05fa4 100644
>>> --- a/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
>>> +++ b/drivers/net/ethernet/marvell/octeontx2/af/cgx.c
>>> @@ -1993,7 +1993,7 @@ static int cgx_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>>>    	nvec = pci_msix_vec_count(cgx->pdev);
>>>    	err = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_MSIX);
>>> -	if (err < 0 || err != nvec) {
>>> +	if (err < 0) {
>>>    		dev_err(dev, "Request for %d msix vectors failed, err %d\n",
>>>    			nvec, err);
>>
>>
>> Now that I think about it more, maybe we want to error out when err != nvec
>> as well ? In that case maybe the right thing to do is leave the check as is
>> and set err = -EXYZ before goto ?
>>
>> Thanks,
>> Harshit>   		goto err_release_regions;
> 
> Hi Harshit,
> 
> My reading of the documentation of pci_alloc_irq_vectors() is that
> Because nvec is passed as both the min and max desired vectors,
> either nvecs will be allocated, or -ENOSPC will be returned.
> 

Ah thats a nice summary of the correctness of this patch.> Maybe it is 
worth adding a comment about that to patch description
> or the code. But I think the code in this patch is correct.

Definitely will add this and send v2.

Thanks,
Harshit