In place kexec

[H. Peter Anvin]

On 07/29/2010 06:43 AM, Neil Horman wrote:
> On Wed, Jul 28, 2010 at 03:02:19PM -0700, Eric W. Biederman wrote:
>> "H. Peter Anvin" <hpa at zytor.com> writes:
>>
>>> We are getting a claim that the qla driver corrupts memory after a
>>> kexec, apparently due to a DMA engine left running in the before-kernel.
>>>
>>> For an in-place kexec (as opposed to a crash dump kexec, where we switch
>>> into dedicated memory), what shutdown paths get executed?
>>
>> It is the normal reboot path, so the device shutdown method gets
>> executed.
>>
>> Eric
>>
> Check your iommu.  We've had lots of problems with them in the past, and in the
> crash path we explicity leave the iommu on now, whereas the normal shutdown path
> turns it off.  If some other dma-capable device doesn't shut down properly and
> keeps dma operations going, you're liable to get memory corruption when the
> iommu re-initalizes.  
> 

Sorry, can we keep the discussions of kexec-on-crash and kexec-in-place
clearly separated, please?  The qla driver issue is supposed to be
kexec-in-place, and it sounds like you're talking about kexec-on-crash.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.