virtio-pci: harden INTX interrupts

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.

Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20211019070152.8236-6-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 3f51fdb7be45431ae562c84cbbef19277197811d..fdbde1db5ec59f7cee313871d7ed5917d0798d20 100644 (file)
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -30,8 +30,16 @@ void vp_disable_cbs(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) {
+               /*
+                * The below synchronize() guarantees that any
+                * interrupt for this line arriving after
+                * synchronize_irq() has completed is guaranteed to see
+                * intx_soft_enabled == false.
+                */
+               WRITE_ONCE(vp_dev->intx_soft_enabled, false);
                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 +51,16 @@ void vp_enable_cbs(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) {
+               disable_irq(vp_dev->pci_dev->irq);
+               /*
+                * The above disable_irq() provides TSO ordering and
+                * as such promotes the below store to store-release.
+                */
+               WRITE_ONCE(vp_dev->intx_soft_enabled, true);
+               enable_irq(vp_dev->pci_dev->irq);
                return;
+       }
 
        for (i = 0; i < vp_dev->msix_vectors; ++i)
                enable_irq(pci_irq_vector(vp_dev->pci_dev, i));
@@ -97,6 +113,9 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
        struct virtio_pci_device *vp_dev = opaque;
        u8 isr;
 
+       if (!READ_ONCE(vp_dev->intx_soft_enabled))
+               return IRQ_NONE;
+
        /* 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 d3c6f72c73906029b5c32451a32ea6c073cbf301..23f6c5c678d5e3e411726f2ebe1d3a009e4f990c 100644 (file)
--- a/drivers/virtio/virtio_pci_common.h
+++ b/drivers/virtio/virtio_pci_common.h
@@ -63,6 +63,7 @@ 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. */