Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH] virtio-net: Read MAC only after initializing MSI-X | Date | Sun, 14 Aug 2011 12:23:44 +0930 |
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On Sat, 13 Aug 2011 11:51:01 +0300, Sasha Levin <levinsasha928@gmail.com> wrote: > The MAC of a virtio-net device is located at the first field of the device > specific header. This header is located at offset 20 if the device doesn't > support MSI-X or offset 24 if it does.
Erk. This means, in general, we have to do virtio_find_single_vq or config->find_vqs before we examine any config options.
Look at virtio_blk, which has the same error.
Solutions in order of best to worst: (1) Enable MSI-X before calling device probe. This means reserving two vectors in virtio_pci_probe to ensure we *can* do this, I think. Michael?
(2) Ensure ordering of "find_vqs then access config space" statically. This probably means handing the vqs array to virtio_config_val, so noone can call it before they have their virtqueues.
(3) Ensure ordering dynamically, ie. BUG_ON() if they haven't done find_vqs when they call the config accessors.
If (1) is too invasive for -stable, then we should rearrange the drivers in separate patches (and cc: -stable), then fix it properly.
Good catch Sasha!
Cheers, Rusty.
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