On Tue, Sep 01, 2026 at 10:07:41PM -0400, Radu Rendec wrote: > Under certain conditions(*) vp_modern_get_status() can always return > 0xff. This has a ripple effect that ultimately makes the system fail to > boot if the drivers are built-in and the virtio devices are probed > during boot: > * vp_reset() for the virtio-net-pci device spins forever in the loop > around vp_modern_get_status(mdev), which always returns 0xff. > * vp_reset() is called in the context of the probe() function for the > virtio-net-pci device, so probe() never returns. > * the init task gets stuck in wait_for_device_probe() before it > executes the real init binary. > > Add a timeout to the reset function and make the device probing fail if > the reset function times out.
Generally, I like using gdb stub in qemu to debug kernel and anything that will make things time out and fail is unwelcome. > > (*) This is not a theoretical problem. It happens on imx8mp-evk under > Qemu due to a relatively recent change to the dw_pcie driver that's > incompatible with the dw_pcie emulation in Qemu. I reported that bug > separately as a follow up to the patch that introduced it: > https://lore.kernel.org/all/[email protected]/ So presumably it will be fixed in qemu? Or find a different way, e.g. poke at device/vendor id of virtio. or add a workaround in the driver if you prefer. > Signed-off-by: Radu Rendec <[email protected]> > --- > drivers/remoteproc/remoteproc_virtio.c | 4 +++- > drivers/virtio/virtio.c | 8 +++++--- > drivers/virtio/virtio_mmio.c | 5 ++++- > drivers/virtio/virtio_pci_legacy.c | 4 +++- > drivers/virtio/virtio_pci_modern.c | 15 ++++++++++++--- > include/linux/virtio.h | 2 +- > include/linux/virtio_config.h | 2 +- > 7 files changed, 29 insertions(+), 11 deletions(-) > > diff --git a/drivers/remoteproc/remoteproc_virtio.c > b/drivers/remoteproc/remoteproc_virtio.c > index d5e9ff045a28..d103b80b1faf 100644 > --- a/drivers/remoteproc/remoteproc_virtio.c > +++ b/drivers/remoteproc/remoteproc_virtio.c > @@ -231,7 +231,7 @@ static void rproc_virtio_set_status(struct virtio_device > *vdev, u8 status) > dev_dbg(&vdev->dev, "status: %d\n", status); > } > > -static void rproc_virtio_reset(struct virtio_device *vdev) > +static int rproc_virtio_reset(struct virtio_device *vdev) > { > struct rproc_vdev *rvdev = vdev_to_rvdev(vdev); > struct fw_rsc_vdev *rsc; > @@ -240,6 +240,8 @@ static void rproc_virtio_reset(struct virtio_device *vdev) > > rsc->status = 0; > dev_dbg(&vdev->dev, "reset !\n"); > + > + return 0; > } > > /* provide the vdev features as retrieved from the firmware */ > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index 75bb4ffe3b87..9542e4f7cb31 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -250,7 +250,7 @@ static int virtio_features_ok(struct virtio_device *dev) > * call/workqueue/bh. Invoking virtio_break_device then flushing any such > * contexts is one way to handle that. > * */ > -void virtio_reset_device(struct virtio_device *dev) > +int virtio_reset_device(struct virtio_device *dev) > { > #ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION > /* > @@ -263,7 +263,7 @@ void virtio_reset_device(struct virtio_device *dev) > virtio_synchronize_cbs(dev); > #endif > > - dev->config->reset(dev); > + return dev->config->reset(dev); > } > EXPORT_SYMBOL_GPL(virtio_reset_device); > > @@ -567,7 +567,9 @@ int register_virtio_device(struct virtio_device *dev) > > /* We always start by resetting the device, in case a previous > * driver messed it up. This also tests that code path a little. */ > - virtio_reset_device(dev); > + err = virtio_reset_device(dev); > + if (err) > + goto out_of_node_put; > > /* Acknowledge that we've seen the device. */ > virtio_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE); > diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c > index 316f03b97356..537d38841331 100644 > --- a/drivers/virtio/virtio_mmio.c > +++ b/drivers/virtio/virtio_mmio.c > @@ -249,7 +249,7 @@ static void vm_set_status(struct virtio_device *vdev, u8 > status) > writel(status, vm_dev->base + VIRTIO_MMIO_STATUS); > } > > -static void vm_reset(struct virtio_device *vdev) > +static int vm_reset(struct virtio_device *vdev) > { > struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev); > > @@ -260,7 +260,10 @@ static void vm_reset(struct virtio_device *vdev) > /* Wait for reset to complete. */ > while (vm_get_status(vdev)) > fsleep(1000); > + /* TODO: add timeout */ > } > + > + return 0; > } > > > diff --git a/drivers/virtio/virtio_pci_legacy.c > b/drivers/virtio/virtio_pci_legacy.c > index d9cbb02b35a1..2882756c7084 100644 > --- a/drivers/virtio/virtio_pci_legacy.c > +++ b/drivers/virtio/virtio_pci_legacy.c > @@ -90,7 +90,7 @@ static void vp_set_status(struct virtio_device *vdev, u8 > status) > vp_legacy_set_status(&vp_dev->ldev, status); > } > > -static void vp_reset(struct virtio_device *vdev) > +static int vp_reset(struct virtio_device *vdev) > { > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > /* 0 status means a reset. */ > @@ -100,6 +100,8 @@ static void vp_reset(struct virtio_device *vdev) > vp_legacy_get_status(&vp_dev->ldev); > /* Flush pending VQ/configuration callbacks. */ > vp_synchronize_vectors(vdev); > + > + return 0; > } > > static u16 vp_config_vector(struct virtio_pci_device *vp_dev, u16 vector) > diff --git a/drivers/virtio/virtio_pci_modern.c > b/drivers/virtio/virtio_pci_modern.c > index 6d8ae2a6a8ca..4a6906a18cfa 100644 > --- a/drivers/virtio/virtio_pci_modern.c > +++ b/drivers/virtio/virtio_pci_modern.c > @@ -21,6 +21,7 @@ > #include "virtio_pci_common.h" > > #define VIRTIO_AVQ_SGS_MAX 4 > +#define VIRTIO_PCI_RESET_TIMEOUT_MS 1000 > > static void vp_get_features(struct virtio_device *vdev, u64 *features) > { > @@ -543,10 +544,11 @@ static void vp_set_status(struct virtio_device *vdev, > u8 status) > vp_modern_avq_activate(vdev); > } > > -static void vp_reset(struct virtio_device *vdev) > +static int vp_reset(struct virtio_device *vdev) > { > struct virtio_pci_device *vp_dev = to_vp_device(vdev); > struct virtio_pci_modern_device *mdev = &vp_dev->mdev; > + int timeout = VIRTIO_PCI_RESET_TIMEOUT_MS; > > /* 0 status means a reset. */ > vp_modern_set_status(mdev, 0); > @@ -555,13 +557,20 @@ static void vp_reset(struct virtio_device *vdev) > * This will flush out the status write, and flush in device writes, > * including MSI-X interrupts, if any. > */ > - while (vp_modern_get_status(mdev)) > - msleep(1); > + while (vp_modern_get_status(mdev)) { > + if (!timeout--) { > + dev_warn(&vdev->dev, "reset timeout"); > + return -ETIMEDOUT; > + } > + msleep(1000); 1 second is a long time. normally devices reset immediately. > + } > > vp_modern_avq_cleanup(vdev); > > /* Flush pending VQ/configuration callbacks. */ > vp_synchronize_vectors(vdev); > + > + return 0; > } > > static int vp_active_vq(struct virtqueue *vq, u16 msix_vec) So now if the device does not reset, during cleanup we previously blocked and now it will corrupt memory. > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > index f923e42cfd01..568e1bd95e4c 100644 > --- a/include/linux/virtio.h > +++ b/include/linux/virtio.h > @@ -212,7 +212,7 @@ void virtio_config_driver_enable(struct virtio_device > *dev); > int virtio_device_freeze(struct virtio_device *dev); > int virtio_device_restore(struct virtio_device *dev); > #endif > -void virtio_reset_device(struct virtio_device *dev); > +int virtio_reset_device(struct virtio_device *dev); > void virtio_device_shutdown(struct virtio_device *dev); > int virtio_device_reset_prepare(struct virtio_device *dev); > int virtio_device_reset_done(struct virtio_device *dev); > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h > index 69f84ea85d71..153426b0ae79 100644 > --- a/include/linux/virtio_config.h > +++ b/include/linux/virtio_config.h > @@ -117,7 +117,7 @@ struct virtio_config_ops { > u32 (*generation)(struct virtio_device *vdev); > u8 (*get_status)(struct virtio_device *vdev); > void (*set_status)(struct virtio_device *vdev, u8 status); > - void (*reset)(struct virtio_device *vdev); > + int (*reset)(struct virtio_device *vdev); > int (*find_vqs)(struct virtio_device *vdev, unsigned int nvqs, > struct virtqueue *vqs[], > struct virtqueue_info vqs_info[], > -- > 2.55.0
