On Wed, Mar 09, 2011 at 12:02:06PM +0530, Mahesh Jagannath Salgaonkar wrote:

On 08/25/2010 06:07 AM, Eric W. Biederman wrote:

quoted

Anton Blanchard [off-list ref] writes:

quoted

On ppc64 the crashkernel region almost always overlaps an area of firmware.
This works fine except when using the sysfs interface to reduce the kdump
region. If we free the firmware area we are guaranteed to crash.

That is ppc64 bug.  firmware should not be in the reserved region.  Any
random kernel like thing can be put in to that region at any valid
address and the fact that shrinking the region frees your firmware means
that using that region could also stomp your firmware (which I assume
would be a bad thing).

The issue only happens while shrinking the region using sysfs interface.
We already have checks in kexec for not to stomp over on the firmware
overlap area while loading capture kernel. Currently we do a top-down
allocation for the firmware region which means it sits at the top of the
RMO, right in the middle of the crashdump region. We can not move the
crashkernel region beyond firmware region because kernel needs its some
of memory in RMO region.

The crashkernel region is specified via kernel cmdline, so why
not just drop a failure when it overlaps with RMO region?
Am I missing something?

Thanks.