Messages in this thread | | | Date | Wed, 5 Sep 2012 22:16:57 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [RFC 1/2] virtio_console: Add support for DMA memory allocation |
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On Wed, Sep 05, 2012 at 08:15:36PM +0200, Sjur Brændeland wrote: > Hi Michael. > > >> If the device then asks for VIRTIO_CONSOLE_F_DMA_MEM > >> when DMA is not supported, virtio will do BUG_ON() from > >> virtio_check_driver_offered_feature(). > >> > >> Is this acceptable or should we add a check in virtcons_probe() > >> and let the probing fail instead? > >> > >> E.g: > >> /* Refuse to bind if F_DMA_MEM request cannot be met */ > >> if (!VIRTIO_CONSOLE_HAS_DMA && > >> (vdev->config->get_features(vdev) & (1 << VIRTIO_CONSOLE_F_DMA_MEM))){ > >> dev_err(&vdev->dev, > >> "DMA_MEM requested, but arch does not support DMA\n"); > >> err = -EINVAL; > >> goto fail; > >> } > >> > >> Regards, > >> Sjur > > > > Failing probe would be cleaner. But there is still a problem: > > old driver will happily bind to that device and then > > fail to work, right? > > Not just fail to work, the kernel will panic on the BUG_ON(). > Remoteproc gets the virtio configuration from firmware loaded > from user space. So this type of problem might be triggered > for other virtio drivers as well.
how?
> > > virtio pci has revision id for this, but remoteproc doesn't > > seem to have anything similar. Or did I miss it? > > No there are currently no sanity check of > virtio type and feature bits in remoteproc. > One option may be to add this...
you can not fix the past.
> > If not - > > we probably need to use a different > > device id, and not a feature bit. > > But if I create a new virtio console type, remoteproc > could still call the existing virtio_console with random > bad feature bits, causing kernel panic.
cirtio core checks device id - this should not happen.
> Even if we fix this particular problem, the general problem > still exists: bogus virtio declarations in remoteproc's firmware > may cause BUG_ON().
which BUG_ON exactly?
> (Note the fundamental difference > between visualizations and remoteproc. For remoteproc > the virtio configuration comes from binaries loaded from > user space). > > So maybe we should look for a more generic solution, e.g. > changing virtio probe functionality so that devices with > bad feature bits will not trigger BUG_ON(), but rather refuse > to bind the driver. > > Regards, > Sjur -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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