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Date: Mon, 13 Sep 2021 02:03:51 -0400
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jason Wang <jasowang@...hat.com>
Cc: virtualization@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org, f.hetzelt@...berlin.de,
david.kaplan@....com, konrad.wilk@...cle.com, pbonzini@...hat.com,
Andi Kleen <ak@...ux.intel.com>,
Dan Williams <dan.j.williams@...el.com>,
"Kuppuswamy, Sathyanarayanan"
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>,
Andy Lutomirski <luto@...nel.org>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Richard Henderson <rth@...ddle.net>,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
James E J Bottomley <James.Bottomley@...senpartnership.com>,
Helge Deller <deller@....de>,
"David S . Miller" <davem@...emloft.net>,
Arnd Bergmann <arnd@...db.de>,
Jonathan Corbet <corbet@....net>,
Peter H Anvin <hpa@...or.com>,
Dave Hansen <dave.hansen@...el.com>,
Tony Luck <tony.luck@...el.com>,
Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
Sean Christopherson <seanjc@...gle.com>,
Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
X86 ML <x86@...nel.org>
Subject: Re: [PATCH 6/9] virtio_pci: harden MSI-X interrupts
On Mon, Sep 13, 2021 at 01:53:50PM +0800, Jason Wang wrote:
> We used to synchronize pending MSI-X irq handlers via
> synchronize_irq(), this may not work for the untrusted device which
> may keep sending interrupts after reset which may lead unexpected
> results. Similarly, we should not enable MSI-X interrupt until the
> device is ready. So this patch fixes those two issues by:
>
> 1) switching to use disable_irq() to prevent the virtio interrupt
> handlers to be called after the device is reset.
> 2) using IRQF_NO_AUTOEN and enable the MSI-X irq during .ready()
>
> This can make sure the virtio interrupt handler won't be called before
> virtio_device_ready() and after reset.
>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
I don't get the threat model here. Isn't disabling irqs done by the
hypervisor anyway? Is there a reason to trust disable_irq but not
device reset?
Cc a bunch more people ...
> ---
> drivers/virtio/virtio_pci_common.c | 27 +++++++++++++++++++++------
> drivers/virtio/virtio_pci_common.h | 6 ++++--
> drivers/virtio/virtio_pci_legacy.c | 5 +++--
> drivers/virtio/virtio_pci_modern.c | 6 ++++--
> 4 files changed, 32 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index b35bb2d57f62..0b9523e6dd39 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -24,8 +24,8 @@ MODULE_PARM_DESC(force_legacy,
> "Force legacy mode for transitional virtio 1 devices");
> #endif
>
> -/* wait for pending irq handlers */
> -void vp_synchronize_vectors(struct virtio_device *vdev)
> +/* disable irq handlers */
> +void vp_disable_vectors(struct virtio_device *vdev)
> {
> struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> int i;
> @@ -34,7 +34,20 @@ void vp_synchronize_vectors(struct virtio_device *vdev)
> synchronize_irq(vp_dev->pci_dev->irq);
>
> for (i = 0; i < vp_dev->msix_vectors; ++i)
> - synchronize_irq(pci_irq_vector(vp_dev->pci_dev, i));
> + disable_irq(pci_irq_vector(vp_dev->pci_dev, i));
> +}
> +
> +/* enable irq handlers */
> +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)
> + return;
> +
> + for (i = 0; i < vp_dev->msix_vectors; ++i)
> + enable_irq(pci_irq_vector(vp_dev->pci_dev, i));
> }
>
> /* the notify function used when creating a virt queue */
> @@ -141,7 +154,8 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
> snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
> "%s-config", name);
> err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
> - vp_config_changed, 0, vp_dev->msix_names[v],
> + vp_config_changed, IRQF_NO_AUTOEN,
> + vp_dev->msix_names[v],
> vp_dev);
> if (err)
> goto error;
> @@ -160,7 +174,8 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
> snprintf(vp_dev->msix_names[v], sizeof *vp_dev->msix_names,
> "%s-virtqueues", name);
> err = request_irq(pci_irq_vector(vp_dev->pci_dev, v),
> - vp_vring_interrupt, 0, vp_dev->msix_names[v],
> + vp_vring_interrupt, IRQF_NO_AUTOEN,
> + vp_dev->msix_names[v],
> vp_dev);
> if (err)
> goto error;
> @@ -337,7 +352,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
> "%s-%s",
> dev_name(&vp_dev->vdev.dev), names[i]);
> err = request_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec),
> - vring_interrupt, 0,
> + vring_interrupt, IRQF_NO_AUTOEN,
> vp_dev->msix_names[msix_vec],
> vqs[i]);
> if (err)
> diff --git a/drivers/virtio/virtio_pci_common.h b/drivers/virtio/virtio_pci_common.h
> index beec047a8f8d..a235ce9ff6a5 100644
> --- a/drivers/virtio/virtio_pci_common.h
> +++ b/drivers/virtio/virtio_pci_common.h
> @@ -102,8 +102,10 @@ static struct virtio_pci_device *to_vp_device(struct virtio_device *vdev)
> return container_of(vdev, struct virtio_pci_device, vdev);
> }
>
> -/* wait for pending irq handlers */
> -void vp_synchronize_vectors(struct virtio_device *vdev);
> +/* disable irq handlers */
> +void vp_disable_vectors(struct virtio_device *vdev);
> +/* enable irq handlers */
> +void vp_enable_vectors(struct virtio_device *vdev);
> /* the notify function used when creating a virt queue */
> bool vp_notify(struct virtqueue *vq);
> /* the config->del_vqs() implementation */
> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> index d62e9835aeec..bdf6bc667ab5 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -97,8 +97,8 @@ static void vp_reset(struct virtio_device *vdev)
> /* Flush out the status write, and flush in device writes,
> * including MSi-X interrupts, if any. */
> ioread8(vp_dev->ioaddr + VIRTIO_PCI_STATUS);
> - /* Flush pending VQ/configuration callbacks. */
> - vp_synchronize_vectors(vdev);
> + /* Disable VQ/configuration callbacks. */
> + vp_disable_vectors(vdev);
> }
>
> static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
> @@ -194,6 +194,7 @@ static void del_vq(struct virtio_pci_vq_info *info)
> }
>
> static const struct virtio_config_ops virtio_pci_config_ops = {
> + .ready = vp_enable_vectors,
> .get = vp_get,
> .set = vp_set,
> .get_status = vp_get_status,
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 30654d3a0b41..acf0f6b6381d 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -172,8 +172,8 @@ static void vp_reset(struct virtio_device *vdev)
> */
> while (vp_modern_get_status(mdev))
> msleep(1);
> - /* Flush pending VQ/configuration callbacks. */
> - vp_synchronize_vectors(vdev);
> + /* Disable VQ/configuration callbacks. */
> + vp_disable_vectors(vdev);
> }
>
> static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector)
> @@ -380,6 +380,7 @@ static bool vp_get_shm_region(struct virtio_device *vdev,
> }
>
> static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
> + .ready = vp_enable_vectors,
> .get = NULL,
> .set = NULL,
> .generation = vp_generation,
> @@ -397,6 +398,7 @@ static const struct virtio_config_ops virtio_pci_config_nodev_ops = {
> };
>
> static const struct virtio_config_ops virtio_pci_config_ops = {
> + .ready = vp_enable_vectors,
> .get = vp_get,
> .set = vp_set,
> .generation = vp_generation,
> --
> 2.25.1
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