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Sun, 12 Sep 2021 23:50:16 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwcfkgu3ConcE2PukWR2cAEy3AU4MhrJ9eakHtv6dPbV1CFh1HXDoihq8fVIZUBqRBUMAYQfw== X-Received: by 2002:adf:fe82:: with SMTP id l2mr5774770wrr.268.1631515816044; Sun, 12 Sep 2021 23:50:16 -0700 (PDT) Received: from redhat.com ([2.55.27.174]) by smtp.gmail.com with ESMTPSA id h8sm5857613wmb.35.2021.09.12.23.50.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 12 Sep 2021 23:50:15 -0700 (PDT) Date: Mon, 13 Sep 2021 02:50:08 -0400 From: "Michael S. Tsirkin" To: Jason Wang Subject: Re: [PATCH 6/9] virtio_pci: harden MSI-X interrupts Message-ID: <20210913024153-mutt-send-email-mst@kernel.org> References: <20210913055353.35219-1-jasowang@redhat.com> <20210913055353.35219-7-jasowang@redhat.com> <20210913015711-mutt-send-email-mst@kernel.org> <20210913022257-mutt-send-email-mst@kernel.org> <20210913023626-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: <20210913023626-mutt-send-email-mst@kernel.org> 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: "Kuppuswamy, Sathyanarayanan" , Kuppuswamy Sathyanarayanan , "kaplan, david" , Peter Zijlstra , virtualization , James E J Bottomley , Dave Hansen , Peter H Anvin , Thomas Gleixner , Andi Kleen , Jonathan Corbet , Helge Deller , X86 ML , Ingo Molnar , Arnd Bergmann , Konrad Rzeszutek Wilk , "Hetzelt, Felicitas" , Tony Luck , Borislav Petkov , Andy Lutomirski , Bjorn Helgaas , Dan Williams , Richard Henderson , Thomas Bogendoerfer , Sean Christopherson , linux-kernel , pbonzini , "David S . Miller" , Kirill Shutemov 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 Mon, Sep 13, 2021 at 02:37:42AM -0400, Michael S. Tsirkin wrote: > On Mon, Sep 13, 2021 at 02:34:01PM +0800, Jason Wang wrote: > > On Mon, Sep 13, 2021 at 2:28 PM Michael S. Tsirkin wrote: > > > > > > On Mon, Sep 13, 2021 at 02:08:02PM +0800, Jason Wang wrote: > > > > On Mon, Sep 13, 2021 at 2:04 PM Michael S. Tsirkin wrote: > > > > > > > > > > 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 > > > > > > > > > > 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? > > > > > > > > My understanding is that e.g in the case of SEV/TDX we don't trust the > > > > hypervisor. So the hypervisor can keep sending interrupts even if the > > > > device is reset. The guest can only trust its own software interrupt > > > > management logic to avoid call virtio callback in this case. > > > > > > > > Thanks > > > > > > Hmm but I don't see how do these patches do this. > > > They call disable_irq but can't the hypervisor keep > > > sending interrupts after disable_irq, too? > > > > Yes, but since the irq is disabled, the vring or config callback won't > > be called in this case. > > > > Thanks > > But doen't "irq is disabled" basically mean "we told the hypervisor > to disable the irq"? What extractly prevents hypervisor from > sending the irq even if guest thinks it disabled it? More generally, can't we for example blow away the indir_desc array that we use to keep the ctx pointers? Won't that be enough? And looking at all this closely, I suspect it is wise to just completely disable hotplug/unplug for encrypted guests. Or maybe it's already the case? > > > > > > > > > > > > > > > > > > > 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 > > > > > > > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization