Subject: Re: [PATCH 7/7] vDPA/ifcvf: improve irq requester, to handle per_vq/shared/config irq

From: "Michael S. Tsirkin" <[email-masked]>
Date: Thu, 13 Jan 2022 05:29:49 -0500

On Thu, Jan 13, 2022 at 06:10:15PM +0800, Zhu, Lingshan wrote:
> 
> 
> On 1/13/2022 5:52 PM, Michael S. Tsirkin wrote:
> > On Thu, Jan 13, 2022 at 04:17:29PM +0800, Zhu, Lingshan wrote:
> > > 
> > > On 1/11/2022 3:11 PM, Zhu, Lingshan wrote:
> > > 
> > > 
> > > 
> > >      On 1/10/2022 2:04 PM, Michael S. Tsirkin wrote:
> > > 
> > >          On Mon, Jan 10, 2022 at 01:18:51PM +0800, Zhu Lingshan wrote:
> > > 
> > >              This commit expends irq requester abilities to handle per vq irq,
> > >              shared irq and config irq.
> > > 
> > >              On some platforms, the device can not get enough vectors for every
> > >              virtqueue and config interrupt, the device needs to work under such
> > >              circumstances.
> > > 
> > >              Normally a device can get enough vectors, so every virtqueue and
> > >              config interrupt can have its own vector/irq. If the total vector
> > >              number is less than all virtqueues + 1(config interrupt), all
> > >              virtqueues need to share a vector/irq and config interrupt is
> > >              enabled. If the total vector number < 2, all vitequeues share
> > >              a vector/irq, and config interrupt is disabled. Otherwise it will
> > >              fail if allocation for vectors fails.
> > > 
> > >              This commit also made necessary chages to the irq cleaner to
> > >              free per vq irq/shared irq and config irq.
> > > 
> > >              Signed-off-by: Zhu Lingshan <[email-masked]>
> > > 
> > >          In this case, shouldn't you also check VIRTIO_PCI_ISR_CONFIG?
> > >          doing that will skip the need
> > > 
> > >      Hello Michael,
> > > 
> > >      When insufficient MSIX vectors granted:
> > >      If num_vectors >=2, there will be a vector for the config interrupt, and all vqs share one vector.
> > >      If num_vectors =1, all vqs share the only one vector, and config interrupt is disabled.
> > ATM linux falls back to INTX in that case, shared by config and vqs.
> Yes, the same result. However this driver needs to drive VFs too, and VFs do
> not support INTX,
> so we need it to send msix dma.
> > 
> > >      currently vqs and config interrupt don't share vectors, so IMHO, no need to check .
> > IMHO it does not matter much that current Linux drivers do not use it,
> > the spec explicitly allows this option. If such hardware
> > becomes more common (and you seem to want to improve support
> > for managing interrupts so maybe yes) we'll add it in Linux.
> (just see your another email coming), so I think I should implement a irq
> handler
> for num_vectors=1 case, a handler checks VIRTIO_PCI_ISR_CONFIG to tell
> whether
> it is a vq interrupt or config interrupt, then handle it(not disabling
> config interrupt).
> 
> Thanks,
> Zhu Lingshan

Right. To be more exact, if status is bit 2 is not set you call
vq interrupt, if set you call both vq and config interrupt,
since with MSI only config interrupts have a status bit.

> > 
> > >      I will send a V2 patch address your comments.
> > > 
> > >      Thanks,
> > >      Zhu Lingshan
> > > 
> > >              ---
> > >               drivers/vdpa/ifcvf/ifcvf_base.h |  6 +--
> > >               drivers/vdpa/ifcvf/ifcvf_main.c | 78 +++++++++++++++------------------
> > >               2 files changed, 38 insertions(+), 46 deletions(-)
> > > 
> > >              diff --git a/drivers/vdpa/ifcvf/ifcvf_base.h b/drivers/vdpa/ifcvf/ifcvf_base.h
> > >              index 1d5431040d7d..1d0afb63f06c 100644
> > >              --- a/drivers/vdpa/ifcvf/ifcvf_base.h
> > >              +++ b/drivers/vdpa/ifcvf/ifcvf_base.h
> > >              @@ -27,8 +27,6 @@
> > > 
> > >               #define IFCVF_QUEUE_ALIGNMENT  PAGE_SIZE
> > >               #define IFCVF_QUEUE_MAX                32768
> > >              -#define IFCVF_MSI_CONFIG_OFF   0
> > >              -#define IFCVF_MSI_QUEUE_OFF    1
> > >               #define IFCVF_PCI_MAX_RESOURCE 6
> > > 
> > >               #define IFCVF_LM_CFG_SIZE              0x40
> > >              @@ -102,11 +100,13 @@ struct ifcvf_hw {
> > >                      u8 notify_bar;
> > >                      /* Notificaiton bar address */
> > >                      void __iomem *notify_base;
> > >              +       u8 vector_per_vq;
> > >              +       u16 padding;
> > > 
> > >          What is this padding doing?
> > > 
> > > for cacheline alignment
> > > 
> > > 
> > > 
> > >                      phys_addr_t notify_base_pa;
> > >                      u32 notify_off_multiplier;
> > >              +       u32 dev_type;
> > >                      u64 req_features;
> > >                      u64 hw_features;
> > >              -       u32 dev_type;
> > > 
> > >          moving things around ... optimization? split out.
> > > 
> > > sure
> > > 
> > > 
> > > 
> > >                      struct virtio_pci_common_cfg __iomem *common_cfg;
> > >                      void __iomem *net_cfg;
> > >                      struct vring_info vring[IFCVF_MAX_QUEUES];
> > >              diff --git a/drivers/vdpa/ifcvf/ifcvf_main.c b/drivers/vdpa/ifcvf/ifcvf_main.c
> > >              index 414b5dfd04ca..ec76e342bd7e 100644
> > >              --- a/drivers/vdpa/ifcvf/ifcvf_main.c
> > >              +++ b/drivers/vdpa/ifcvf/ifcvf_main.c
> > >              @@ -17,6 +17,8 @@
> > >               #define DRIVER_AUTHOR   "Intel Corporation"
> > >               #define IFCVF_DRIVER_NAME       "ifcvf"
> > > 
> > >              +static struct vdpa_config_ops ifc_vdpa_ops;
> > >              +
> > > 
> > >          there can be multiple devices thinkably.
> > >          reusing a global ops does not sound reasonable.
> > > 
> > > OK, I will set vq irq number to -EINVAL when vqs share irq,
> > > then we can disable irq_bypass when see irq = -EINVAL,
> > > no need to set get_vq_irq = NULL.
> > > 
> > > 
> > > 
> > > 
> > >               static irqreturn_t ifcvf_config_changed(int irq, void *arg)
> > >               {
> > >                      struct ifcvf_hw *vf = arg;
> > >              @@ -63,13 +65,20 @@ static void ifcvf_free_irq(struct ifcvf_adapter *adapter, int queues)
> > >                      struct ifcvf_hw *vf = &adapter->vf;
> > >                      int i;
> > > 
> > >              +       if (vf->vector_per_vq)
> > >              +               for (i = 0; i < queues; i++) {
> > >              +                       devm_free_irq(&pdev->dev, vf->vring[i].irq, &vf->vring[i]);
> > >              +                       vf->vring[i].irq = -EINVAL;
> > >              +               }
> > >              +       else
> > >              +               devm_free_irq(&pdev->dev, vf->vring[0].irq, vf);
> > > 
> > >              -       for (i = 0; i < queues; i++) {
> > >              -               devm_free_irq(&pdev->dev, vf->vring[i].irq, &vf->vring[i]);
> > >              -               vf->vring[i].irq = -EINVAL;
> > >              +
> > >              +       if (vf->config_irq != -EINVAL) {
> > >              +               devm_free_irq(&pdev->dev, vf->config_irq, vf);
> > >              +               vf->config_irq = -EINVAL;
> > >                      }
> > > 
> > >          what about other error types?
> > > 
> > > vf->config_irq is set to -EINVAL in ifcvf_request_config_irq(),
> > > if no config irq(vector) is granted, or it should be a valid irq number,
> > > so there can be no other error numbers. But I can change it
> > > to  if (vf->config_irq < 0) for sure
> > > 
> > > 
> > > 
> > > 
> > >              -       devm_free_irq(&pdev->dev, vf->config_irq, vf);
> > >                      ifcvf_free_irq_vectors(pdev);
> > >               }
> > > 
> > >              @@ -191,52 +200,35 @@ static int ifcvf_request_config_irq(struct ifcvf_adapter *adapter, int config_ve
> > > 
> > >               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_vectors;
> > >              +       int config_vector, ret;
> > > 
> > >              -       /* all queues and config interrupt  */
> > >              -       max_intr = vf->nr_vring + 1;
> > >              +       nvectors = ifcvf_alloc_vectors(adapter);
> > >              +       if (nvectors < 0)
> > >              +               return nvectors;
> > > 
> > >              -       ret = pci_alloc_irq_vectors(pdev, max_intr,
> > >              -                                   max_intr, PCI_IRQ_MSIX);
> > >              -       if (ret < 0) {
> > >              -               IFCVF_ERR(pdev, "Failed to alloc IRQ vectors\n");
> > >              -               return ret;
> > >              -       }
> > >              +       vf->vector_per_vq = true;
> > >              +       max_vectors = vf->nr_vring + 1;
> > >              +       config_vector = vf->nr_vring;
> > > 
> > >              -       snprintf(vf->config_msix_name, 256, "ifcvf[%s]-config\n",
> > >              -                pci_name(pdev));
> > >              -       vector = 0;
> > >              -       vf->config_irq = pci_irq_vector(pdev, vector);
> > >              -       ret = devm_request_irq(&pdev->dev, vf->config_irq,
> > >              -                              ifcvf_config_changed, 0,
> > >              -                              vf->config_msix_name, vf);
> > >              -       if (ret) {
> > >              -               IFCVF_ERR(pdev, "Failed to request config irq\n");
> > >              -               return ret;
> > >              +       if (nvectors < max_vectors) {
> > >              +               vf->vector_per_vq = false;
> > >              +               config_vector = 1;
> > >              +               ifc_vdpa_ops.get_vq_irq = NULL;
> > >                      }
> > > 
> > >              -       for (i = 0; i < vf->nr_vring; 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);
> > >              +       if (nvectors < 2)
> > >              +               config_vector = 0;
> > > 
> > >              -                       return ret;
> > >              -               }
> > >              +       ret = ifcvf_request_vq_irq(adapter, vf->vector_per_vq);
> > >              +       if (ret)
> > >              +               return ret;
> > > 
> > >              -               vf->vring[i].irq = irq;
> > >              -       }
> > >              +       ret = ifcvf_request_config_irq(adapter, config_vector);
> > >              +
> > >              +       if (ret)
> > >              +               return ret;
> > > 
> > >          here on error we need to cleanup vq irq we requested, need we not?
> > > 
> > > I think it may not be needed, it can work without config interrupt, though lame
> > > 
> > > Thanks for your comments!
> > > Zhu Lingshan
> > > 
> > > 
> > > 
> > > 
> > >                      return 0;
> > >               }
> > >              @@ -573,7 +565,7 @@ static struct vdpa_notification_area ifcvf_get_vq_notification(struct vdpa_devic
> > >                * IFCVF currently does't have on-chip IOMMU, so not
> > >                * implemented set_map()/dma_map()/dma_unmap()
> > >                */
> > >              -static const struct vdpa_config_ops ifc_vdpa_ops = {
> > >              +static struct vdpa_config_ops ifc_vdpa_ops = {
> > >                      .get_features   = ifcvf_vdpa_get_features,
> > >                      .set_features   = ifcvf_vdpa_set_features,
> > >                      .get_status     = ifcvf_vdpa_get_status,
> > >              --
> > >              2.27.0
> > > 
> > > 
> > > 
> > >