netdev - Re: [PATCH net v3 1/4] net: txgbe: initialize num_q

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Message-ID: <ZoQbChC5gTNxBNtI@localhost.localdomain>
Date: Tue, 2 Jul 2024 17:21:46 +0200
From: Michal Kubiak <michal.kubiak@...el.com>
To: Jiawen Wu <jiawenwu@...stnetic.com>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <horms@...nel.org>, <andrew@...n.ch>,
	<netdev@...r.kernel.org>, <przemyslaw.kitszel@...el.com>,
	<mengyuanlou@...-swift.com>, <duanqiangwen@...-swift.com>
Subject: Re: [PATCH net v3 1/4] net: txgbe: initialize num_q_vectors for
 MSI/INTx interrupts

On Mon, Jul 01, 2024 at 03:14:13PM +0800, Jiawen Wu wrote:
> When using MSI/INTx interrupts, wx->num_q_vectors is uninitialized.
> Thus there will be kernel panic in wx_alloc_q_vectors() to allocate
> queue vectors.
> 
> Fixes: 3f703186113f ("net: libwx: Add irq flow functions")
> Signed-off-by: Jiawen Wu <jiawenwu@...stnetic.com>
> ---
>  drivers/net/ethernet/wangxun/libwx/wx_lib.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/wangxun/libwx/wx_lib.c b/drivers/net/ethernet/wangxun/libwx/wx_lib.c
> index 68bde91b67a0..f53776877f71 100644
> --- a/drivers/net/ethernet/wangxun/libwx/wx_lib.c
> +++ b/drivers/net/ethernet/wangxun/libwx/wx_lib.c
> @@ -1686,6 +1686,7 @@ static int wx_set_interrupt_capability(struct wx *wx)
>  	}
>  
>  	pdev->irq = pci_irq_vector(pdev, 0);
> +	wx->num_q_vectors = 1;

I would suggest improving readability of that logic. TBH, initially it wasn't
obvious to me why you assign 1 to num_q_vectors (instead of nvecs variable).
Maybe you just want to exit with an error when nvecs != 1 and avoid some nesting.
I think that should make that logic easier to read. For example:

        /* minmum one for queue, one for misc*/
        nvecs = 1;
        nvecs = pci_alloc_irq_vectors(pdev, nvecs,
                                      nvecs, PCI_IRQ_MSI | PCI_IRQ_INTX);
        if (nvecs != 1) {
                wx_err(wx, "Failed to allocate MSI/INTx interrupts. Error: %d\n", nvecs);
                return nvecs;
        }

        if (pdev->msi_enabled)
                wx_err(wx, "Fallback to MSI.\n");
        else
                wx_err(wx, "Fallback to INTx.\n");

        pdev->irq = pci_irq_vector(pdev, 0);
	wx->num_q_vectors = 1;

(Please consider it as a suggestion only).
>  
>  	return 0;
>  }
> -- 
> 2.27.0
> 
> 

Thanks,
Michal