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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
Date: Tue, 9 Jun 2020 11:17:27 +0200
Message-ID: <20200609091727.GA23814@lst.de> (raw)
In-Reply-To: <s5hlfkwip1h.wl-tiwai@suse.de>

On Tue, Jun 09, 2020 at 11:09:14AM +0200, Takashi Iwai wrote:
> On Tue, 09 Jun 2020 10:43:05 +0200,
> Christoph Hellwig wrote:
> > 
> > On Tue, Jun 09, 2020 at 10:05:26AM +0200, Takashi Iwai wrote:
> > > > >From the disassembly it seems like a vmalloc allocation is NULL, which
> > > > seems really weird as this patch shouldn't make a difference for them,
> > > > and I also only see a single places that allocates the field, and that
> > > > checks for an allocation failure.  But the sound code is a little
> > > > hard to unwind sometimes.
> > > 
> > > It's not clear which sound device being affected, but if it's
> > > HD-audio on x86, runtime->dma_area points to a vmapped buffer from
> > > SG-pages allocated by dma_alloc_coherent().
> > > 
> > > OTOH, if it's a USB-audio, runtime->dma_area is a buffer by
> > > vmalloc().
> > 
> > Err, you can't just vmap a buffer returned from dma_alloc_coherent,
> > dma_alloc_coherent returns values are opaque and can't be used
> > for virt_to_page.  Whatever that code did has already been broken
> > per the DMA API contract and on many architectures and just happend
> > to work on x86 by accident.
> 
> Hmm, that's bad.
> 
> 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.

  reply index

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-20 11:11 Pavel Machek
2020-05-20 11:37 ` Takashi Iwai
2020-05-20 11:39   ` Pavel Machek
2020-05-20 11:43     ` Takashi Iwai
2020-06-07 15:58 ` Alex Xu (Hello71)
2020-06-07 16:38   ` 82fef0ad811f "x86/mm: unencrypted non-blocking DMA allocations use coherent pools" was " Pavel Machek
2020-06-07 19:41     ` David Rientjes
2020-06-07 22:53       ` Alex Xu (Hello71)
2020-06-08  0:57         ` David Rientjes
2020-06-08  2:13           ` Alex Xu (Hello71)
2020-06-08  6:19   ` Christoph Hellwig
2020-06-08 13:53     ` Alex Xu (Hello71)
2020-06-09  2:31       ` David Rientjes
2020-06-09  5:43         ` Christoph Hellwig
2020-06-09  8:05           ` Takashi Iwai
2020-06-09  8:43             ` Christoph Hellwig
2020-06-09  9:09               ` Takashi Iwai
2020-06-09  9:17                 ` Christoph Hellwig [this message]
2020-06-09  9:31                   ` Takashi Iwai
2020-06-09 11:02                     ` Takashi Iwai
2020-06-09 11:31                     ` Christoph Hellwig
2020-06-09 11:38                       ` Takashi Iwai
2020-06-09 11:40                         ` Christoph Hellwig
2020-06-09 11:45                           ` Takashi Iwai
2020-06-09 11:49                             ` Christoph Hellwig
2020-06-09 13:16                               ` Jaroslav Kysela
2020-06-10  5:26           ` David Rientjes
2020-06-10  7:14             ` Christoph Hellwig
2020-06-09 11:47       ` Christoph Hellwig
2020-06-09 15:12         ` Takashi Iwai
     [not found]           ` <<s5hr1uogtna.wl-tiwai@suse.de>
2020-06-11 14:51             ` Alex Xu (Hello71)
2020-06-11 17:11               ` Takashi Iwai
2020-06-13 16:25                 ` Alex Xu (Hello71)
2020-06-14  9:54                   ` Takashi Iwai
2020-06-14 12:07                     ` Alex Xu (Hello71)
2020-06-14 15:40                       ` Takashi Iwai
2020-06-11 14:51         ` Alex Xu (Hello71)
     [not found] <20200520110900.GA8203@amd>
2020-05-21  7:41 ` Pavel Machek

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