linux-arm-kernel.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: Robin Murphy <robin.murphy@arm.com>
To: "Marek Behún" <kabel@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Arnd Bergmann <arnd@kernel.org>,
	Andre Przywara <andre.przywara@arm.com>,
	Marc Zyngier <maz@kernel.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Russell King <linux@armlinux.org.uk>,
	Andrew Lunn <andrew@lunn.ch>,
	Gregory Clement <gregory.clement@bootlin.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	iommu@lists.linux-foundation.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally"
Date: Fri, 30 Sep 2022 17:41:44 +0100	[thread overview]
Message-ID: <50ec473b-9def-dc2b-7d1b-cbdc277cbac2@arm.com> (raw)
In-Reply-To: <20220930170205.490f1a6b@dellmb>

On 2022-09-30 16:02, Marek Behún wrote:
> On Fri, 30 Sep 2022 16:52:34 +0200
> Marek Behún <kabel@kernel.org> wrote:
> 
>> On Fri, 30 Sep 2022 14:46:06 +0100
>> Robin Murphy <robin.murphy@arm.com> wrote:
>>
>>> On 2022-09-30 14:10, Marek Behún wrote:
>>>> Hello Linus, Arnd, Robin and Christoph,
>>>>
>>>> I just bisected a regression on Turris Omnia (Armada 385), wherein the
>>>> system hangs shortly after init is run, to commit
>>>>
>>>>     ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
>>>>     https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ae626eb97376
>>>>
>>>> In order to fix the regression, I had to revert this commit and
>>>> subsequent 3 commits:
>>>>     ae626eb97376 ("ARM/dma-mapping: use dma-direct unconditionally")
>>>>     42998ef08aba ("ARM/dma-mapping: drop .dma_supported for IOMMU ops")
>>>>     d563bccfa35b ("ARM/dma-mapping: consolidate IOMMU ops callbacks")
>>>>     4136ce90f079 ("ARM/dma-mapping: merge IOMMU ops")
>>>> in reverse order, of course:
>>>>     git revert 4136ce90f079
>>>>     git revert d563bccfa35b
>>>>     git revert 42998ef08aba
>>>>     git revert ae626eb97376
>>>>
>>>> Christoph, Robin, since you are the authors of these commits, do you
>>>> have any idea what could be happening? Are we able to fix this without
>>>> reverting those commits, before 6.0?
>>>
>>> "hangs shortly after init" isn't much to go on. Are any errors logged?
>>> Possibly some driver is sat waiting for a DMA transfer to complete, that
>>> has somehow got the wrong address or lost coherency so never gets seen,
>>> but without at least being able to narrow it down to the affected driver
>>> it's hard to do much more than vague guessing.
>>
>> OK I enabled CONFIG_DMA_API_DEBUG and now am getting a null pointer
>> dereference. I managed to isolate the bug to a specifc line in mvneta
>> driver:
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/marvell/mvneta.c#n2591
>>
>> I put debug printfs (pr_err("  a %i\n", __LINE__)) into the
>> mvneta_rx_hwbm() function.
>> The pr_err after the call to dma_sync_single_range_for_cpu() prints,
>> but the pr_err after skb_put_data() does not print.
>>
>> Attaching console output.
> 
> It seems that the null pointer dereference comes from the data variable
> having zero value. We assign
>    data = (u8 *)(uintptr_t)rx_desc->buf_cookie;
> rx_desc is obtained with function
>    mvneta_rxq_next_desc_get()
> 
> rx queues are allocated in mvneta_rxq_sw_init() with
> 
>    /* Allocate memory for RX descriptors */
>    rxq->descs = dma_alloc_coherent(pp->dev->dev.parent,
> 				  rxq->size * MVNETA_DESC_ALIGNED_SIZE,
> 				  &rxq->descs_phys, GFP_KERNEL);

Hmm, making sense of that driver is beyond me at this time on a Friday 
afternoon, and I can't tell whether this is immediately related, but:

[   10.406446] Register r5 information: 0-page vmalloc region starting 
at 0xf10f3000 allocated at dma_common_contiguous_remap+0x68/0x84

definitely smells suspicious in its own right. Remapping 0 pages is bad 
enough, but I'm also slightly wondering about remapping DMA allocations 
at all - IIUC this is one of the mvebu SoCs where everything gets made 
coherent by a bus notifier, so I wouldn't expect remaps except for 
highmem, but the upstream DT suggests you probably don't have masses of 
RAM either :/

Thanks,
Robin.

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2022-09-30 16:43 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-30 13:10 REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally" Marek Behún
2022-09-30 13:46 ` Robin Murphy
2022-09-30 14:52   ` Marek Behún
2022-09-30 15:02     ` Marek Behún
2022-09-30 16:41       ` Robin Murphy [this message]
2022-09-30 18:02         ` Marek Behún
2022-10-03  7:21           ` Christoph Hellwig
2022-10-03  7:30       ` Christoph Hellwig
2022-10-03 14:11         ` Russell King (Oracle)
2022-10-03 15:25           ` Marek Behún
2022-10-03 16:09             ` Pali Rohár
2022-10-03 19:04               ` Marek Behún
2022-10-03 19:08                 ` Pali Rohár
2022-10-03 21:30             ` Marcin Wojtas
2022-10-03 21:35               ` Pali Rohár
2022-10-03 22:03                 ` Marcin Wojtas
2022-10-04  7:10               ` Christoph Hellwig
2022-10-04  8:15                 ` Marek Behún
2022-10-04  8:17                   ` [PATCH] ARM: mvebu: select OF_DMA_DEFAULT_COHERENT if MACH_MVEBU_V7 Marek Behún
2022-10-04  8:30                     ` Christoph Hellwig
2022-10-04 12:54                       ` Marek Behún
2022-10-04  8:30                     ` Arnd Bergmann
2022-10-04  9:14                     ` Thorsten Leemhuis
2022-10-04  9:22                       ` Russell King (Oracle)
2022-10-04  9:56                 ` REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally" Robin Murphy
2022-10-04  7:25               ` Russell King (Oracle)
2022-10-04  8:30                 ` Marcin Wojtas
2022-10-04  9:08                   ` Russell King (Oracle)
2022-10-04 12:36                     ` Marek Behún
2022-10-04 12:59                       ` Marcin Wojtas
2022-10-04 18:51                         ` Pali Rohár
2022-10-04 19:35                           ` Marcin Wojtas
2022-10-04  8:26               ` Marek Behún
2022-10-04  8:36                 ` Marcin Wojtas
2022-10-20 18:22                   ` Russell King (Oracle)
2022-10-20 19:10                     ` Marek Behún
2022-10-21 16:25                     ` Linus Torvalds
2022-10-21 16:30                     ` Christoph Hellwig
2022-10-21 18:21                       ` Russell King (Oracle)
2022-10-23 11:58                     ` Klaus Kudielka
2022-10-03 18:57         ` Marek Behún
2022-10-01  9:31 ` Thorsten Leemhuis
2022-11-04 12:08   ` REGRESSION in 6.0-rc7 caused by patch "ARM/dma-mapping: use dma-direct unconditionally" #forregzbot Thorsten Leemhuis

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=50ec473b-9def-dc2b-7d1b-cbdc277cbac2@arm.com \
    --to=robin.murphy@arm.com \
    --cc=andre.przywara@arm.com \
    --cc=andrew@lunn.ch \
    --cc=arnd@kernel.org \
    --cc=gregkh@linuxfoundation.org \
    --cc=gregory.clement@bootlin.com \
    --cc=hch@lst.de \
    --cc=iommu@lists.linux-foundation.org \
    --cc=kabel@kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux@armlinux.org.uk \
    --cc=maz@kernel.org \
    --cc=torvalds@linux-foundation.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).