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Tsirkin" To: Jason Wang Subject: Re: [PATCH V2 07/12] virtio-pci: harden INTX interrupts Message-ID: <20211013053627-mutt-send-email-mst@kernel.org> References: <20211012065227.9953-1-jasowang@redhat.com> <20211012065227.9953-8-jasowang@redhat.com> MIME-Version: 1.0 In-Reply-To: <20211012065227.9953-8-jasowang@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: "Paul E . McKenney" , david.kaplan@amd.com, konrad.wilk@oracle.com, Peter Zijlstra , Boqun Feng , f.hetzelt@tu-berlin.de, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Thomas Gleixner X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" 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 > Cc: Thomas Gleixner > Cc: Peter Zijlstra > Cc: Paul E. McKenney > Signed-off-by: Jason Wang > --- > 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 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization