+ Jason Wang (email got truncated). On Fri, Jul 12, 2024 at 07:59:14PM +0530, Manivannan Sadhasivam wrote: > Virtio spec has so far only supported MSI-X and INTX for receiving the > interrupts from the virtio device on PCI transport. But this becomes a > limiting factor for devices supporting only MSI (plus INTX emulation) as > they have to use the legacy INTX emulation which is limited to one IRQ per > PCIe function. > > But this now addressed with the help of a proposal to the Virtio spec > adding MSI support [1]. Based on that, let's implement MSI support in the > virtio-pci driver. > > The Virtio spec proposal reuses the existing MSI-X infrastructure, like the > config_msix_vector/queue_msix_vector fields of the Virito common config > structure. Following that, MSI support in virtio-pci driver is also added > on top of the existing MSI-X implementation and it mostly reuses the MSI-X > code base. The existing vp_find_vqs_msix() API is modified to support MSI > along with MSI-X. > > The preference for interrupt allocation is still given to MSI-X as per the > spec. The driver will try to allocate MSI only if both of the MSI-X > allocations (one vector for each queue and 2 vectors) fails. As like MSI-X, > driver will try to allocate one MSI vector for each queue first, and if > that fails, it will try to allocate 2 vectors (one for config queue and one > shared for queues). If both of them fails, driver will fallback to the > legacy INTX as usual. > > For keeping the changes minimal, existing 'virtio_pci_device::msix_enabled' > flag is used to indicate the status of MSI and MSI-X. Rest of the MSI-X > functionalities such as IRQ affinity are also reused for MSI (but the > affinity setting really depends on the underlying IRQCHIP controller). > > [1] > https://lore.kernel.org/virtio-comment/20240712140144.12066-1-manivannan.sadhasi...@linaro.org/ > > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasi...@linaro.org> > --- > drivers/virtio/virtio_pci_common.c | 24 ++++++++++++++++++------ > drivers/virtio/virtio_pci_common.h | 2 +- > 2 files changed, 19 insertions(+), 7 deletions(-) > > diff --git a/drivers/virtio/virtio_pci_common.c > b/drivers/virtio/virtio_pci_common.c > index f6b0b00e4599..6f80b0c46c5f 100644 > --- a/drivers/virtio/virtio_pci_common.c > +++ b/drivers/virtio/virtio_pci_common.c > @@ -100,11 +100,11 @@ static irqreturn_t vp_interrupt(int irq, void *opaque) > } > > static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors, > - bool per_vq_vectors, struct irq_affinity > *desc) > + bool per_vq_vectors, struct irq_affinity > *desc, > + unsigned int flags) > { > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > const char *name = dev_name(&vp_dev->vdev.dev); > - unsigned int flags = PCI_IRQ_MSIX; > unsigned int i, v; > int err = -ENOMEM; > > @@ -288,7 +288,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, > unsigned int nvqs, > struct virtqueue *vqs[], vq_callback_t *callbacks[], > const char * const names[], bool per_vq_vectors, > const bool *ctx, > - struct irq_affinity *desc) > + struct irq_affinity *desc, unsigned int flags) > { > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > u16 msix_vec; > @@ -310,7 +310,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, > unsigned int nvqs, > } > > err = vp_request_msix_vectors(vdev, nvectors, per_vq_vectors, > - per_vq_vectors ? desc : NULL); > + per_vq_vectors ? desc : NULL, flags); > if (err) > goto error_find; > > @@ -407,11 +407,23 @@ int vp_find_vqs(struct virtio_device *vdev, unsigned > int nvqs, > int err; > > /* Try MSI-X with one vector per queue. */ > - err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, true, ctx, > desc); > + err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, true, ctx, > + desc, PCI_IRQ_MSIX); > if (!err) > return 0; > /* Fallback: MSI-X with one vector for config, one shared for queues. */ > - err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, > desc); > + err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, > + desc, PCI_IRQ_MSIX); > + if (!err) > + return 0; > + /* Try MSI with one vector per queue. */ > + err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, true, ctx, > + desc, PCI_IRQ_MSI); > + if (!err) > + return 0; > + /* Fallback: MSI with one vector for config, one shared for queues. */ > + err = vp_find_vqs_msix(vdev, nvqs, vqs, callbacks, names, false, ctx, > + desc, PCI_IRQ_MSI); > if (!err) > return 0; > /* Is there an interrupt? If not give up. */ > diff --git a/drivers/virtio/virtio_pci_common.h > b/drivers/virtio/virtio_pci_common.h > index 7fef52bee455..a5062ca85f3b 100644 > --- a/drivers/virtio/virtio_pci_common.h > +++ b/drivers/virtio/virtio_pci_common.h > @@ -77,7 +77,7 @@ struct virtio_pci_device { > > struct virtio_pci_admin_vq admin_vq; > > - /* MSI-X support */ > + /* MSI/MSI-X support */ > int msix_enabled; > int intx_enabled; > cpumask_var_t *msix_affinity_masks; > -- > 2.25.1 >
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