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Date:   Tue, 9 Jun 2020 13:40:59 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Takashi Iwai <tiwai@suse.de>
Cc:     Christoph Hellwig <hch@lst.de>,
        David Rientjes <rientjes@google.com>,
        "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>,
        alsa-devel@alsa-project.org, bp@alien8.de, hch@infradead.org,
        hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@redhat.com,
        Pavel Machek <pavel@ucw.cz>, perex@perex.cz,
        tglx@linutronix.de, tiwai@suse.com, x86@kernel.org
Subject: Re: next-0519 on thinkpad x60: sound related? window manager crash
Message-ID: <20200609114059.GA1228@lst.de>
References: <1591624340.z01ejtod28.none@localhost> <alpine.DEB.2.22.394.2006081928070.148886@chino.kir.corp.google.com> <20200609054306.GA9606@lst.de> <s5hsgf4irzt.wl-tiwai@suse.de> <20200609084305.GA21671@lst.de> <s5hlfkwip1h.wl-tiwai@suse.de> <20200609091727.GA23814@lst.de> <s5hh7vkio0n.wl-tiwai@suse.de> <20200609113123.GA547@lst.de> <s5h3674ii49.wl-tiwai@suse.de>
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On Tue, Jun 09, 2020 at 01:38:46PM +0200, Takashi Iwai wrote:
> On Tue, 09 Jun 2020 13:31:23 +0200,
> Christoph Hellwig wrote:
> > 
> > On Tue, Jun 09, 2020 at 11:31:20AM +0200, Takashi Iwai wrote:
> > > > > How would be a proper way to get the virtually mapped SG-buffer pages
> > > > > with coherent memory?  (Also allowing user-space mmap, too)
> > > > 
> > > > dma_mmap_coherent / dma_mmap_attrs for userspace.  We don't really
> > > > have a good way for kernel space mappings.
> > > 
> > > And that's the missing piece right now...  :-<
> > 
> > Can you point me to the relevant places (allocation and vmap mostly)
> > so that I can take a look at how to fix this mess?
> 
> Found in sound/core/sgbuf.c.  It's specific to x86.

So it looks like we could just turn off CONFIG_SND_DMA_SGBUF and
be done with it?  After all this works on other architectures
just fine..