netdev - Re: [PATCH V2 2/4] vDPA/ifcvf: implement device MSIX vector allocator

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Date:   Tue, 25 Jan 2022 14:36:10 -0500
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Zhu Lingshan <lingshan.zhu@...el.com>
Cc:     jasowang@...hat.com, netdev@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH V2 2/4] vDPA/ifcvf: implement device MSIX vector allocator

On Tue, Jan 25, 2022 at 05:17:42PM +0800, Zhu Lingshan wrote:
> This commit implements a MSIX vector allocation helper
> for vqs and config interrupts.
> 
> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
> ---
>  drivers/vdpa/ifcvf/ifcvf_main.c | 30 ++++++++++++++++++++++++++++--
>  1 file changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
> index d1a6b5ab543c..7e2af2d2aaf5 100644
> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> @@ -58,14 +58,40 @@ static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
>  	ifcvf_free_irq_vectors(pdev);
>  }
>  
> +static int ifcvf_alloc_vectors(struct ifcvf_adapter *adapter)


So the helper returns an int...

> +{
> +	struct pci_dev *pdev = adapter->pdev;
> +	struct ifcvf_hw *vf = &adapter->vf;
> +	u16 max_intr, ret;
> +
> +	/* all queues and config interrupt  */
> +	max_intr = vf->nr_vring + 1;
> +	ret = pci_alloc_irq_vectors(pdev, 1, max_intr, PCI_IRQ_MSIX | PCI_IRQ_AFFINITY);
> +
> +	if (ret < 0) {
> +		IFCVF_ERR(pdev, "Failed to alloc IRQ vectors\n");
> +		return ret;


which is negative on error...

> +	}
> +
> +	if (ret < max_intr)
> +		IFCVF_INFO(pdev,
> +			   "Requested %u vectors, however only %u allocated, lower performance\n",
> +			   max_intr, ret);
> +
> +	return ret;
> +}
> +
>  static int ifcvf_request_irq(struct ifcvf_adapter *adapter)
>  {
>  	struct pci_dev *pdev = adapter->pdev;
>  	struct ifcvf_hw *vf = &adapter->vf;
>  	int vector, i, ret, irq;
> -	u16 max_intr;
> +	u16 nvectors, max_intr;
> +
> +	nvectors = ifcvf_alloc_vectors(adapter);

which you proceed to stash into an unsigned int ...

> +	if (!(nvectors > 0))

and then compare to zero ...

> +		return nvectors;
>

correct error handling is unlikely as a result.

  
> -	/* all queues and config interrupt  */
>  	max_intr = vf->nr_vring + 1;
>  
>  	ret = pci_alloc_irq_vectors(pdev, max_intr,


As long as you are introducing a helper, document it's return
type and behaviour and then use correctly.

> -- 
> 2.27.0