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Tsirkin" To: Jason Wang Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, f.hetzelt@tu-berlin.de, david.kaplan@amd.com, konrad.wilk@oracle.com Subject: Re: [PATCH 7/9] virtio-pci: harden INTX interrupts Message-ID: <20210913022824-mutt-send-email-mst@kernel.org> References: <20210913055353.35219-1-jasowang@redhat.com> <20210913055353.35219-8-jasowang@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210913055353.35219-8-jasowang@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 13, 2021 at 01:53:51PM +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. > > Signed-off-by: Jason Wang Not all that excited about all the memory barriers for something that should be an extremely rare event (for most kernels - literally once per boot). Can't we do better? > --- > drivers/virtio/virtio_pci_common.c | 18 ++++++++++++++++-- > drivers/virtio/virtio_pci_common.h | 1 + > 2 files changed, 17 insertions(+), 2 deletions(-) > > diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c > index 0b9523e6dd39..835197151dc1 100644 > --- a/drivers/virtio/virtio_pci_common.c > +++ b/drivers/virtio/virtio_pci_common.c > @@ -30,8 +30,12 @@ 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) { > + vp_dev->intx_soft_enabled = false; > + /* ensure the vp_interrupt see this intx_soft_enabled value */ > + smp_wmb(); > 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 +47,12 @@ 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) { > + vp_dev->intx_soft_enabled = true; > + /* ensure the vp_interrupt see this intx_soft_enabled value */ > + smp_wmb(); > return; > + } > > for (i = 0; i < vp_dev->msix_vectors; ++i) > enable_irq(pci_irq_vector(vp_dev->pci_dev, i)); > @@ -97,6 +105,12 @@ static irqreturn_t vp_interrupt(int irq, void *opaque) > struct virtio_pci_device *vp_dev = opaque; > u8 isr; > > + if (!vp_dev->intx_soft_enabled) > + return IRQ_NONE; > + > + /* read intx_soft_enabled before read others */ > + smp_rmb(); > + > /* 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