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Message-ID: <24d5875e-6f44-ce43-74f0-e641e02f8f42@redhat.com>
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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