Revert "virtio-pci: harden INTX interrupts"

This reverts commit 080cd7c. Since
the MSI-X interrupts hardening will be reverted in the next patch. We
will rework the interrupt hardening in the future.

Fixes: 080cd7c ("virtio-pci: harden INTX interrupts")
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20220323031524.6555-1-jasowang@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: jasowang

drivers/virtio/virtio_pci_common.c

@@ -30,16 +30,8 @@ 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) {
-		/*
-		 * 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);
+	if (vp_dev->intx_enabled)
 		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));
@@ -51,16 +43,8 @@ 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) {
-		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);
+	if (vp_dev->intx_enabled)
 		return;
-	}
 
 	for (i = 0; i < vp_dev->msix_vectors; ++i)
 		enable_irq(pci_irq_vector(vp_dev->pci_dev, i));
@@ -113,9 +97,6 @@ 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);

drivers/virtio/virtio_pci_common.h

@@ -63,7 +63,6 @@ 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. */