From: David Rientjes <rientjes@google.com>
To: Christoph Hellwig <hch@lst.de>
Cc: "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 22:26:45 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.22.394.2006092213110.154443@chino.kir.corp.google.com> (raw)
In-Reply-To: <20200609054306.GA9606@lst.de>
On Tue, 9 Jun 2020, Christoph Hellwig wrote:
> > Working theory is that CONFIG_DMA_NONCOHERENT_MMAP getting set is causing
> > the error_code in the page fault path. Debugging with Alex off-thread we
> > found that dma_{alloc,free}_from_pool() are not getting called from the
> > new code in dma_direct_{alloc,free}_pages() and he has not enabled
> > mem_encrypt.
>
> While DMA_COHERENT_POOL absolutely should not select DMA_NONCOHERENT_MMAP
> (and you should send your patch either way), I don't think it is going
> to make a difference here, as DMA_NONCOHERENT_MMAP just means we
> allows mmaps even for non-coherent devices, and we do not support
> non-coherent devices on x86.
>
We haven't heard yet whether the disabling of DMA_NONCOHERENT_MMAP fixes
Aaron's BUG(), and the patch included some other debugging hints that will
be printed out in case it didn't, but I'll share what we figured out:
In 5.7, his config didn't have DMA_DIRECT_REMAP or DMA_REMAP (it did have
GENERIC_ALLOCATOR already). AMD_MEM_ENCRYPT is set.
In Linus HEAD, AMD_MEM_ENCRYPT now selects DMA_COHERENT_POOL so it sets
the two aforementioned options.
We also figured out that dma_should_alloc_from_pool() is always false up
until the BUG(). So what else changed? Only the selection of DMA_REMAP
and DMA_NONCOHERENT_MMAP.
The comment in the Kconfig about setting "an uncached bit in the
pagetables" led me to believe it may be related to the splat he's seeing
(reserved bit violation). So I suggested dropping DMA_NONCOHERENT_MMAP
from his Kconfig for testing purposes.
If this option should not implicitly be set for DMA_COHERENT_POOL, then I
assume we need yet another Kconfig option since DMA_REMAP selected it
before and DMA_COHERENT_POOL selects DMA_REMAP :)
So do we want a DMA_REMAP_BUT_NO_DMA_NONCOHERENT_MMAP? Decouple DMA_REMAP
from DMA_NONCOHERENT_MMAP and select the latter wherever the former was
set (but not DMA_COHERENT_POOL)? Something else?
next prev parent reply other threads:[~2020-06-10 5:26 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-20 11:11 next-0519 on thinkpad x60: sound related? window manager crash 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
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 [this message]
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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