Re: [virtio] [OASIS Issue Tracker] Created: (VIRTIO-35) race condition with multi-dword config accesses

From
Pawel Moll <>
Date
2013-10-08T10:39:13+00:00
ID
1381228750.3228.13.camel@hornet
Thread
Re: [virtio] [OASIS Issue Tracker] Created: (VIRTIO-35) race condition with multi-dword config accesses
On Fri, 2013-10-04 at 04:36 +0100, Rusty Russell wrote:
> +• 0x018 | R | ConfigGeneration
> + Configuration atomicity value.
> + Changes every time the configuration noticeably changes.  This means the
> + device may only change the value after a configuration read operation,
> + but it must change if there is any risk of a device seeing an inconsistent
> + configuration state.

How about moving it closer to the config space? Something like 0x0f0 or
even 0x0fc?

> +2.3.2.2.1. Legacy Interface: MMIO Device Layout
> +--------------------------
> +The ConfigGeneration field does not exist in legacy devices; fortunately
> +it would return 0 if accessed.  

Not on "my" models, no. It would result in external abort (think
SIGBUS).

Not a big problem - the device version number will be bumped to 2 anyway
(working on it right now).

Paweł