linux-kernel - Re: BUG: NULL pointer dereference at 00000000 -- IP: [<f8e783d5>] :b43:b43_dma_mapping

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Date:	Tue, 10 Jun 2008 16:50:26 +0200
From:	Michael Buesch <mb@...sch.de>
To:	"Vegard Nossum" <vegard.nossum@...il.com>
Cc:	"Miles Lane" <miles.lane@...il.com>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	"FUJITA Tomonori" <fujita.tomonori@....ntt.co.jp>
Subject: Re: BUG: NULL pointer dereference at 00000000 -- IP: [<f8e783d5>] :b43:b43_dma_mapping_error+0x16/0x155

On Tuesday 10 June 2008 16:42:41 Vegard Nossum wrote:
> This change comes from
> 
> commit 353c409463ecba63c3a41a992d3f5fba935eada9
> Author: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
> Date:   Fri May 23 19:02:30 2008 +0000


Ok, FUJITA Tomonori, please make sure a patch like the following goes
into the same trees that you submitted commit 353c409 to.
Also make sure to check b43legacy. I _guess_ you might have added
the same bug there.

Index: wireless-testing/drivers/net/wireless/b43/dma.c
===================================================================
--- wireless-testing.orig/drivers/net/wireless/b43/dma.c	2008-06-10 13:58:22.000000000 +0200
+++ wireless-testing/drivers/net/wireless/b43/dma.c	2008-06-10 16:48:53.000000000 +0200
@@ -802,6 +802,7 @@ struct b43_dmaring *b43_setup_dmaring(st
 	if (!ring)
 		goto out;
 	ring->type = type;
+	ring->dev = dev;
 
 	nr_slots = B43_RXRING_SLOTS;
 	if (for_tx)
@@ -853,7 +854,6 @@ struct b43_dmaring *b43_setup_dmaring(st
 				 DMA_TO_DEVICE);
 	}
 
-	ring->dev = dev;
 	ring->nr_slots = nr_slots;
 	ring->mmio_base = b43_dmacontroller_base(type, controller_index);
 	ring->index = controller_index;


>     dma-mapping-add-the-device-argument-to-dma_mapping_error
> 
>     Add per-device dma_mapping_ops support for CONFIG_X86_64 as POWER
>     architecture does:
> 
>     This enables us to cleanly fix the Calgary IOMMU issue that some devices
>     are not behind the IOMMU (http://lkml.org/lkml/2008/5/8/423).
> 
>     I think that per-device dma_mapping_ops support would be also helpful for
>     KVM people to support PCI passthrough but Andi thinks that this makes it
>     difficult to support the PCI passthrough (see the above thread).  So I
>     CC'ed this to KVM camp.  Comments are appreciated.
> 
>     A pointer to dma_mapping_ops to struct dev_archdata is added.  If the
>     pointer is non NULL, DMA operations in asm/dma-mapping.h use it.  If it's
>     NULL, the system-wide dma_ops pointer is used as before.
> 
>     If it's useful for KVM people, I plan to implement a mechanism to register
>     a hook called when a new pci (or dma capable) device is created (it works
>     with hot plugging).  It enables IOMMUs to set up an appropriate
>     dma_mapping_ops per device.
> 
>     The major obstacle is that dma_mapping_error doesn't take a pointer to the
>     device unlike other DMA operations.  So x86 can't have dma_mapping_ops per
>     device.  Note all the POWER IOMMUs use the same dma_mapping_error function
>     so this is not a problem for POWER but x86 IOMMUs use different
>     dma_mapping_error functions.
> 
>     The first patch adds the device argument to dma_mapping_error.  The patch
>     is trivial but large since it touches lots of drivers and dma-mapping.h in
>     all the architecture.
> 
> (Added to Cc.)
> 
> 
> Vegard
> 



-- 
Greetings Michael.
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