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Date:   Tue, 12 May 2020 11:38:18 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "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6:11, Zhu, Lingshan wrote:
>
>
> On 5/11/2020 5:26 PM, 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.
> Hi Jason,
>
> So these code can a double assurance.
>>
>>
>>>
>>> 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);
> we have the loop in ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues),
> it takes a parameter queues, and a loop
>
> +    for (i = 0; i < queues; i++)+        devm_free_irq(&pdev->dev, 
> vf->vring[i].irq, &vf->vring[i]); will free irq for vq[0,queues)


Aha, I get this.


>>
>>
>>
>>> +
>>> +            return ret;
>>> +        }
>>> +
>>> +        vf->vring[i].irq = irq;
>>> +    }
>>> +
>>> +    return 0;
>>> +}
>>> +
>>>   static int ifcvf_start_datapath(void *private)
>>>   {
>>>       struct ifcvf_hw *vf = ifcvf_private_to_vf(private);
>>> @@ -118,9 +172,12 @@ static void ifcvf_vdpa_set_status(struct 
>>> vdpa_device *vdpa_dev, u8 status)
>>>   {
>>>       struct ifcvf_adapter *adapter;
>>>       struct ifcvf_hw *vf;
>>> +    u8 status_old;
>>> +    int ret;
>>>         vf  = vdpa_to_vf(vdpa_dev);
>>>       adapter = dev_get_drvdata(vdpa_dev->dev.parent);
>>> +    status_old = ifcvf_get_status(vf);
>>>         if (status == 0) {
>>>           ifcvf_stop_datapath(adapter);
>>> @@ -128,7 +185,22 @@ static void ifcvf_vdpa_set_status(struct 
>>> vdpa_device *vdpa_dev, u8 status)
>>>           return;
>>>       }
>>>   -    if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
>>> +    if ((status_old & VIRTIO_CONFIG_S_DRIVER_OK) &&
>>> +        !(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
>>> +        ifcvf_stop_datapath(adapter);
>>> +        ifcvf_free_irq(adapter, IFCVF_MAX_QUEUE_PAIRS * 2);
>>> +    }
>>> +
>>> +    if ((status & VIRTIO_CONFIG_S_DRIVER_OK) &&
>>> +        !(status_old & VIRTIO_CONFIG_S_DRIVER_OK)) {
>>> +        ret = ifcvf_request_irq(adapter);
>>> +        if (ret) {
>>> +            status = ifcvf_get_status(vf);
>>> +            status |= VIRTIO_CONFIG_S_FAILED;
>>> +            ifcvf_set_status(vf, status);
>>> +            return;
>>> +        }
>>> +
>>
>>
>> Have a hard though on the logic here.
>>
>> This depends on the status setting from guest or userspace. Which 
>> means it can not deal with e.g when qemu or userspace is crashed? Do 
>> we need to care this or it's a over engineering?
>>
>> Thanks
> If qemu crash, I guess users may re-run qmeu / re-initialize the device, according to the spec, there should be a reset routine.
> This code piece handles status change on DRIVER_OK flipping. I am not sure I get your point, mind to give more hints?


The problem is if we don't launch new qemu instance, the interrupt will 
be still there?

Thanks


>
> Thanks,
> BR
> Zhu Lingshan
>   
>>
>>
>>>           if (ifcvf_start_datapath(adapter) < 0)
>>>               IFCVF_ERR(adapter->pdev,
>>>                     "Failed to set ifcvf vdpa  status %u\n",
>>> @@ -284,38 +356,6 @@ static void ifcvf_vdpa_set_config_cb(struct 
>>> vdpa_device *vdpa_dev,
>>>       .set_config_cb  = ifcvf_vdpa_set_config_cb,
>>>   };
>>>   -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;
>>> -
>>> -
>>> -    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);
>>> -            return ret;
>>> -        }
>>> -        vf->vring[i].irq = irq;
>>> -    }
>>> -
>>> -    return 0;
>>> -}
>>> -
>>> -static void ifcvf_free_irq_vectors(void *data)
>>> -{
>>> -    pci_free_irq_vectors(data);
>>> -}
>>> -
>>>   static int ifcvf_probe(struct pci_dev *pdev, const struct 
>>> pci_device_id *id)
>>>   {
>>>       struct device *dev = &pdev->dev;
>>> @@ -349,13 +389,6 @@ static int ifcvf_probe(struct pci_dev *pdev, 
>>> const struct pci_device_id *id)
>>>           return ret;
>>>       }
>>>   -    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;
>>> -    }
>>> -
>>>       ret = devm_add_action_or_reset(dev, ifcvf_free_irq_vectors, 
>>> pdev);
>>>       if (ret) {
>>>           IFCVF_ERR(pdev,
>>> @@ -379,12 +412,6 @@ static int ifcvf_probe(struct pci_dev *pdev, 
>>> const struct pci_device_id *id)
>>>       adapter->pdev = pdev;
>>>       adapter->vdpa.dma_dev = &pdev->dev;
>>>   -    ret = ifcvf_request_irq(adapter);
>>> -    if (ret) {
>>> -        IFCVF_ERR(pdev, "Failed to request MSI-X irq\n");
>>> -        goto err;
>>> -    }
>>> -
>>>       ret = ifcvf_init_hw(vf, pdev);
>>>       if (ret) {
>>>           IFCVF_ERR(pdev, "Failed to init IFCVF hw\n");
>>

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