linux-kernel - Re: [Pkg-xen-devel] ioatdma: Boot process hangs then reboots when using Xen + Linux 3.2

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Date:	Fri, 2 Mar 2012 11:31:56 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Dan Williams <dan.j.williams@...el.com>,
	Jonathan Nieder <jrnieder@...il.com>,
	xen-devel@...ts.xensource.com,
	pkg-xen-devel@...ts.alioth.debian.org,
	Maciej Sosnowski <maciej.sosnowski@...el.com>,
	linux-kernel@...r.kernel.org, William Dauchy <wdauchy@...il.com>,
	Konrad Rzeszutek Wilk <konrad@...nok.org>,
	Dave Jiang <dave.jiang@...el.com>
Subject: Re: [Pkg-xen-devel] ioatdma: Boot process hangs then reboots when
 using Xen + Linux 3.2

On Fri, Mar 2, 2012 at 9:57 AM, Bastian Blank <waldi@...ian.org> wrote:
> On Fri, Mar 02, 2012 at 08:44:00AM -0800, Dan Williams wrote:
>> On Fri, Mar 2, 2012 at 8:21 AM, Bastian Blank <waldi@...ian.org> wrote:
>> > On Thu, Mar 01, 2012 at 10:42:44PM -0800, Dan Williams wrote:
>> >> WARN_ON may work, but then kernel may be subject random hangs from missed
>> >> i/o completions.
>> ...actually descriptors completing too early.
>
> The interrupt happens while the module is still loading, so most likely
> directly after enabling them. There should be no request in flight yet.
>
> What puzzles me is the mix of different data types in the ioatdma
> driver:
>
> | u64 completion = *chan->completion;
> | unsigned long phys_complete = completion & ~0x3f;
>
> The state is 64bit long, but is down converted to a 32bit value without
> anything.
>
> phys_complete (a 32 bit value) gets compared to struct
> dma_async_tx_descriptor.phys, which is defined as dma_addr_t, a _64_ bit
> value.

The assumption is that the driver's control structures are not in high
memory so all address values will only have 32-bits of valid data, but
maybe xen32 changes that assumption?

Can you send the log of the driver load with debug enabled?

diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
index a4d6cb0..82472de 100644
--- a/drivers/dma/ioat/dma.c
+++ b/drivers/dma/ioat/dma.c
@@ -24,7 +24,7 @@
  * This driver supports an Intel I/OAT DMA engine, which does asynchronous
  * copy operations.
  */
-
+#define DEBUG
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/slab.h>
diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
index 5d65f83..da337e7 100644
--- a/drivers/dma/ioat/dma_v2.c
+++ b/drivers/dma/ioat/dma_v2.c
@@ -24,7 +24,7 @@
  * This driver supports an Intel I/OAT DMA engine (versions >= 2), which
  * does asynchronous data movement and checksumming operations.
  */
-
+#define DEBUG
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/slab.h>
--
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