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
On Wed, Oct 13, 2021 at 5:42 PM Michael S. Tsirkin <mst at redhat.com> wrote:> > 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.Yes.> 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.But the interrupt could be raised after synchronize_irq() which may see a false of the intx_soft_enabled. In this case we still need the make sure intx_soft_enbled to be read first instead of allowing other operations to be done first, otherwise the intx_soft_enabled is meaningless. Thanks> > 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 >