linux-kernel - Re: [PATCH] ifcvf: move IRQ request/free to status change handlers

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Message-ID: <289e3487-7ecc-6b82-35d5-3037e34c8e31@redhat.com>
Date:   Tue, 12 May 2020 11:41:10 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Francesco Lavra <francescolavra.fl@...il.com>,
        Zhu Lingshan <lingshan.zhu@...el.com>, mst@...hat.com,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc:     lulu@...hat.com, dan.daly@...el.com, cunming.liang@...el.com
Subject: Re: [PATCH] ifcvf: move IRQ request/free to status change handlers


On 2020/5/11 下午6:18, Francesco Lavra wrote:
> On 5/11/20 11:26 AM, Jason Wang wrote:
>>
>> On 2020/5/11 下午3:19, Zhu Lingshan wrote:
>>> This commit move IRQ request and free operations from probe()
>>> to VIRTIO status change handler to comply with VIRTIO spec.
>>>
>>> VIRTIO spec 1.1, section 2.1.2 Device Requirements: Device Status Field
>>> The device MUST NOT consume buffers or send any used buffer
>>> notifications to the driver before DRIVER_OK.
>>
>>
>> My previous explanation might be wrong here. It depends on how you 
>> implement your hardware, if you hardware guarantee that no interrupt 
>> will be triggered before DRIVER_OK, then it's fine.
>>
>> And the main goal for this patch is to allocate the interrupt on demand.
>>
>>
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>> ---
>>>   drivers/vdpa/ifcvf/ifcvf_main.c | 119 
>>> ++++++++++++++++++++++++----------------
>>>   1 file changed, 73 insertions(+), 46 deletions(-)
>>>
>>> diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c 
>>> b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> index abf6a061..4d58bf2 100644
>>> --- a/drivers/vdpa/ifcvf/ifcvf_main.c
>>> +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
>>> @@ -28,6 +28,60 @@ static irqreturn_t ifcvf_intr_handler(int irq, 
>>> void *arg)
>>>       return IRQ_HANDLED;
>>>   }
>>> +static void ifcvf_free_irq_vectors(void *data)
>>> +{
>>> +    pci_free_irq_vectors(data);
>>> +}
>>> +
>>> +static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
>>> +{
>>> +    struct pci_dev *pdev = adapter->pdev;
>>> +    struct ifcvf_hw *vf = &adapter->vf;
>>> +    int i;
>>> +
>>> +
>>> +    for (i = 0; i < queues; i++)
>>> +        devm_free_irq(&pdev->dev, vf->vring[i].irq, &vf->vring[i]);
>>> +
>>> +    ifcvf_free_irq_vectors(pdev);
>>> +}
>>> +
>>> +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;
>>> +
>>> +    ret = pci_alloc_irq_vectors(pdev, IFCVF_MAX_INTR,
>>> +                    IFCVF_MAX_INTR, PCI_IRQ_MSIX);
>>> +    if (ret < 0) {
>>> +        IFCVF_ERR(pdev, "Failed to alloc IRQ vectors\n");
>>> +        return ret;
>>> +    }
>>> +
>>> +    for (i = 0; i < IFCVF_MAX_QUEUE_PAIRS * 2; i++) {
>>> +        snprintf(vf->vring[i].msix_name, 256, "ifcvf[%s]-%d\n",
>>> +             pci_name(pdev), i);
>>> +        vector = i + IFCVF_MSI_QUEUE_OFF;
>>> +        irq = pci_irq_vector(pdev, vector);
>>> +        ret = devm_request_irq(&pdev->dev, irq,
>>> +                       ifcvf_intr_handler, 0,
>>> +                       vf->vring[i].msix_name,
>>> +                       &vf->vring[i]);
>>> +        if (ret) {
>>> +            IFCVF_ERR(pdev,
>>> +                  "Failed to request irq for vq %d\n", i);
>>> +            ifcvf_free_irq(adapter, i);
>>
>>
>> I'm not sure this unwind is correct. It looks like we should loop and 
>> call devm_free_irq() for virtqueue [0, i);
>
> That's exactly what the code does: ifcvf_free_irq() contains a (i = 0; 
> i < queues; i++) loop, and here the function is called with the 
> `queues` argument set to `i`.
>

Oh right.

Thanks