From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Christoph Hellwig <hch@lst.de>
Cc: "Marek Behún" <kabel@kernel.org>,
"Robin Murphy" <robin.murphy@arm.com>,
"Arnd Bergmann" <arnd@kernel.org>,
"Andre Przywara" <andre.przywara@arm.com>,
"Marc Zyngier" <maz@kernel.org>,
"Linus Torvalds" <torvalds@linux-foundation.org>,
"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: Mon, 3 Oct 2022 15:11:44 +0100 [thread overview]
Message-ID: <YzrtoNYtmEmftrjU@shell.armlinux.org.uk> (raw)
In-Reply-To: <20221003073037.GB2108@lst.de>
On Mon, Oct 03, 2022 at 09:30:37AM +0200, Christoph Hellwig wrote:
> On Fri, Sep 30, 2022 at 05:02:05PM +0200, Marek Behún wrote:
> > 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;
>
> I never see any assignment to ->buf_cookie in the driver, what am
> I missing?
I think Marek's setup (like my setups) use the hardware buffer manager,
and it's hardware that fills in the "buf_cookie", which is supposed to
be the virtual address of the buffer.
Each buffer supplied to the hardware buffer manager is supposed to
contain the virtual address in the first 32-bit word in that buffer.
This is done by mvneta_bm_construct():
/* In order to update buf_cookie field of RX descriptor properly,
* BM hardware expects buf virtual address to be placed in the
* first four bytes of mapped buffer.
*/
*(u32 *)buf = (u32)buf;
immediately prior to dma_map_single(..., DMA_FROM_DEVICE) is called.
If I had to guess, I would suggest that this write is being lost via
cache invalidation, and given that the hardware BM both reads and
writes this buffer, DMA_FROM_DEVICE is not correct, it should be
DMA_BIDIRECTIONAL.
Changing that is probably going to need DMA_FROM_DEVICE also changed
elsewhere in the mvneta_bm and mvneta driver.
I'm not in a position where I could test that out. Marek?
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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next prev parent reply other threads:[~2022-10-03 14:13 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
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) [this message]
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
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