linux-kernel - Re: dma api errors with swiotlb

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Message-ID: <20190904131638.GA29164@infradead.org>
Date:   Wed, 4 Sep 2019 06:16:38 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Thomas Hellström (VMware) 
        <thomas_os@...pmail.org>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: dma api errors with swiotlb

On Wed, Sep 04, 2019 at 03:02:14PM +0200, Thomas Hellström (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.