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Subject: Re: [PATCH] ifcvf: move IRQ request/free to status change handlers
To:     Zhu Lingshan <lingshan.zhu@intel.com>, mst@redhat.com,
        kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Cc:     lulu@redhat.com, dan.daly@intel.com, cunming.liang@intel.com
References: <1589181563-38400-1-git-send-email-lingshan.zhu@intel.com>
From:   Jason Wang <jasowang@redhat.com>
Message-ID: <22d9dcdb-e790-0a68-ba41-b9530b2bf9fd@redhat.com>
Date:   Mon, 11 May 2020 17:26:49 +0800
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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@intel.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);


> +
> +			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 (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");