Re: dma api errors with swiotlb

From: Thomas HellstrÃm (VMware)
Date: Wed Sep 04 2019 - 09:22:02 EST

On 9/4/19 3:16 PM, Christoph Hellwig wrote:
On Wed, Sep 04, 2019 at 03:02:14PM +0200, Thomas HellstrÃm (VMware) wrote:
It looks like it does that, although when we send it, the SWIOTLB error has
already occured and been printed out, and then the sequence starts again.
Well, the only way to really find out is to try. We also have a
backoff algorithm in the SCSI midlayer, so it should not be much of
an inpact. If you care about the warnings they can be disabled using
DMA_ATTR_NO_WARN. I have to admit that I'm not even sure the warnings
are all that useful, but that's something you need to take up with
the swiotlb maintainer.

Yes, I guess so. I actually think the warnings make sense, since while the scsi midlayer handles this nicely, other drivers competing for the space might not.