Re: [PATCH 2.6.20.3] Flush writes to MSI-X table

Greg KH
2007-03-23T21:24:31Z

On Thu, Mar 22, 2007 at 02:08:19PM -0700, Mitch Williams wrote:
> Because both MSI-X interrupt messages and MSI-X table writes are posted,
> it's possible for them to cross while in-flight. This results in
> interrupts being received long after the kernel thinks they're disabled,
> and in interrupts being sent to stale vectors after rebalancing.
>
> This patch performs a read flush after writes to the MSI-X table for
> enable/disable and rebalancing operations. Because this is an expensive
> operation, we do not perform the read flush after mask/unmask
> operations. Hardware which supports MSI-X typically also supports some
> sort of interrupt moderation, so a read-flush is not necessary for
> mask/unmask operations.
>
> This patch has been validated with (unreleased) network hardware which
> uses MSI-X.

Is this needed for any hardware that is public today?

Also, it seems a bit too big of a patch for -stable right now,
especially as the mainline patch will not make it into 2.6.22 at the
earliest.

thanks,

greg k-h