linux-kernel - Re: [PATCH net 3/4] net: hns3: fixed vf get max channels bug

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Message-ID: <20250705082403.0ba474f4@pumpkin>
Date: Sat, 5 Jul 2025 08:24:03 +0100
From: David Laight <david.laight.linux@...il.com>
To: Simon Horman <horms@...nel.org>
Cc: Jijie Shao <shaojijie@...wei.com>, davem@...emloft.net,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 andrew+netdev@...n.ch, shenjian15@...wei.com, liuyonglong@...wei.com,
 chenhao418@...wei.com, jonathan.cameron@...wei.com,
 shameerali.kolothum.thodi@...wei.com, salil.mehta@...wei.com,
 netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 3/4] net: hns3: fixed vf get max channels bug

On Fri, 4 Jul 2025 17:05:37 +0100
Simon Horman <horms@...nel.org> wrote:

> + David Laight
> 
> On Wed, Jul 02, 2025 at 09:09:00PM +0800, Jijie Shao wrote:
> > From: Hao Lan <lanhao@...wei.com>
> > 
> > Currently, the queried maximum of vf channels is the maximum of channels
> > supported by each TC. However, the actual maximum of channels is
> > the maximum of channels supported by the device.
> > 
> > Fixes: 849e46077689 ("net: hns3: add ethtool_ops.get_channels support for VF")
> > Signed-off-by: Jian Shen <shenjian15@...wei.com>
> > Signed-off-by: Hao Lan <lanhao@...wei.com>
> > Signed-off-by: Jijie Shao <shaojijie@...wei.com>  
> 
> Reviewed-by: Simon Horman <horms@...nel.org>
> 
> > ---
> >  drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c | 6 +-----
> >  1 file changed, 1 insertion(+), 5 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c b/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c
> > index 33136a1e02cf..626f5419fd7d 100644
> > --- a/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c
> > +++ b/drivers/net/ethernet/hisilicon/hns3/hns3vf/hclgevf_main.c
> > @@ -3094,11 +3094,7 @@ static void hclgevf_uninit_ae_dev(struct hnae3_ae_dev *ae_dev)
> >  
> >  static u32 hclgevf_get_max_channels(struct hclgevf_dev *hdev)
> >  {
> > -	struct hnae3_handle *nic = &hdev->nic;
> > -	struct hnae3_knic_private_info *kinfo = &nic->kinfo;
> > -
> > -	return min_t(u32, hdev->rss_size_max,
> > -		     hdev->num_tqps / kinfo->tc_info.num_tc);
> > +	return min_t(u32, hdev->rss_size_max, hdev->num_tqps);  
> 
> min_t() wasn't needed before and it certainly doesn't seem to be needed
> now, as both .rss_size_max, and .num_tqps are u16.

It (well something) would have been needed before the min_t() changes.
The u16 values get promoted to 'signed int' prior to the division.

> 
> As a follow-up, once this change hits net-next, please update to use min()
> instead. Likely elsewhere too.

Especially any min_t(u16, ...) or u8 ones.
They are just so wrong and have caused bugs.

	David