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

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Date:   Wed, 26 Jan 2022 20:18:37 +0800
From:   "Zhu, Lingshan" <lingshan.zhu@...el.com>
To:     "Michael S. Tsirkin" <mst@...hat.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 1/26/2022 3:36 AM, Michael S. Tsirkin wrote:
> 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...
can fix in V3, thanks for your help!
>
>> +{
>> +	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