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 at gmail.com>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Paul E. McKenney <paulmck at kernel.org>
Signed-off-by: Jason Wang <jasowang at redhat.com>
---
drivers/virtio/virtio_pci_common.c | 24 ++++++++++++++++++++++--
drivers/virtio/virtio_pci_common.h | 1 +
2 files changed, 23 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_pci_common.c
b/drivers/virtio/virtio_pci_common.c
index 0b9523e6dd39..5ae6a2a4eb77 100644
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -30,8 +30,16 @@ 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) {
+ /*
+ * 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_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) {
+ 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 +113,10 @@ static irqreturn_t vp_interrupt(int irq, void *opaque)
struct virtio_pci_device *vp_dev = opaque;
u8 isr;
+ /* read intx_soft_enabled before read others */
+ if (!smp_load_acquire(&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 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
Michael S. Tsirkin
2021-Oct-13 09:42 UTC
[PATCH V2 07/12] virtio-pci: harden INTX interrupts
On Tue, Oct 12, 2021 at 02:52:22PM +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. > > Cc: Boqun Feng <boqun.feng at gmail.com> > Cc: Thomas Gleixner <tglx at linutronix.de> > Cc: Peter Zijlstra <peterz at infradead.org> > Cc: Paul E. McKenney <paulmck at kernel.org> > Signed-off-by: Jason Wang <jasowang at redhat.com> > --- > drivers/virtio/virtio_pci_common.c | 24 ++++++++++++++++++++++-- > drivers/virtio/virtio_pci_common.h | 1 + > 2 files changed, 23 insertions(+), 2 deletions(-) > > diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c > index 0b9523e6dd39..5ae6a2a4eb77 100644 > --- a/drivers/virtio/virtio_pci_common.c > +++ b/drivers/virtio/virtio_pci_common.c > @@ -30,8 +30,16 @@ 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) { > + /* > + * 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_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) { > + 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 +113,10 @@ static irqreturn_t vp_interrupt(int irq, void *opaque) > struct virtio_pci_device *vp_dev = opaque; > u8 isr; > > + /* read intx_soft_enabled before read others */ > + if (!smp_load_acquire(&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);I don't see why we need this ordering guarantee here. synchronize_irq above makes sure no interrupt handler is in progress. the handler itself thus does not need any specific order, it is ok if intx_soft_enabled is read after, not before the rest of it. Just READ_ONCE should be enough, and we can drop the comment.> 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