On Mon, Sep 13, 2021 at 01:53:51PM +0800, Jason Wang wrote:
> This patch tries to make sure the virtio interrupt handler for INTX
> won't be called after a reset and before virtio_device_ready(). We
> can't use IRQF_NO_AUTOEN since we're using shared interrupt
> (IRQF_SHARED). So this patch tracks the INTX enabling status in a new
> intx_soft_enabled variable and toggle it during in
> vp_disable/enable_vectors(). The INTX interrupt handler will check
> intx_soft_enabled before processing the actual interrupt.
>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Not all that excited about all the memory barriers for something
that should be an extremely rare event (for most kernels -
literally once per boot). Can't we do better?
> ---
> drivers/virtio/virtio_pci_common.c | 18 ++++++++++++++++--
> drivers/virtio/virtio_pci_common.h | 1 +
> 2 files changed, 17 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index 0b9523e6dd39..835197151dc1 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -30,8 +30,12 @@ void vp_disable_vectors(struct virtio_device *vdev)
> struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> int i;
>
> - if (vp_dev->intx_enabled)
> + if (vp_dev->intx_enabled) {
> + vp_dev->intx_soft_enabled = false;
> + /* ensure the vp_interrupt see this intx_soft_enabled value */
> + smp_wmb();
> synchronize_irq(vp_dev->pci_dev->irq);
> + }
>
> for (i = 0; i < vp_dev->msix_vectors; ++i)
> disable_irq(pci_irq_vector(vp_dev->pci_dev, i));
> @@ -43,8 +47,12 @@ void vp_enable_vectors(struct virtio_device *vdev)
> struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> int i;
>
> - if (vp_dev->intx_enabled)
> + if (vp_dev->intx_enabled) {
> + vp_dev->intx_soft_enabled = true;
> + /* ensure the vp_interrupt see this intx_soft_enabled value */
> + smp_wmb();
> return;
> + }
>
> for (i = 0; i < vp_dev->msix_vectors; ++i)
> enable_irq(pci_irq_vector(vp_dev->pci_dev, i));
> @@ -97,6 +105,12 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
> struct virtio_pci_device *vp_dev = opaque;
> u8 isr;
>
> + if (!vp_dev->intx_soft_enabled)
> + return IRQ_NONE;
> +
> + /* read intx_soft_enabled before read others */
> + smp_rmb();
> +
> /* reading the ISR has the effect of also clearing it so it's very
> * important to save off the value. */
> isr = ioread8(vp_dev->isr);
> diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
> index a235ce9ff6a5..3c06e0f92ee4 100644
> --- a/drivers/virtio/virtio_pci_common.h
> +++ b/drivers/virtio/virtio_pci_common.h
> @@ -64,6 +64,7 @@ struct virtio_pci_device {
> /* MSI-X support */
> int msix_enabled;
> int intx_enabled;
> + bool intx_soft_enabled;
> cpumask_var_t *msix_affinity_masks;
> /* Name strings for interrupts. This size should be enough,
> * and I'm too lazy to allocate each name separately. */
> --
> 2.25.1
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