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powerpc: Disable Collaborative Memory Manager for kdump

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When running Active Memory Sharing, the Collaborative Memory Manager
(CMM) may mark some pages as "loaned" with the hypervisor.
Periodically, the CMM will query the hypervisor for a loan request,
which is a single signed value.  When kexec'ing into a kdump kernel,
the CMM driver in the kdump kernel is not aware of the pages the
previous kernel had marked as "loaned", so the hypervisor and the CMM
driver are out of sync.  This results in the CMM driver getting a
negative loan request, which can then get treated as a large unsigned
value and can cause kdump to hang due to the CMM driver inflating too
large.  Since there really is no clean way for the CMM driver in the
kdump kernel to clean this up, simply disable CMM in the kdump kernel.
This fixes hangs we were seeing doing kdump with AMS.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
Brian King 2008-12-18 11:13:46 +00:00 committed by Paul Mackerras
parent 5d84e4bee0
commit 2218108e18
1 changed files with 1 additions and 1 deletions
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arch/powerpc/platforms/pseries/Kconfig
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@ -54,7 +54,7 @@ config PPC_SMLPAR
config CMM
tristate "Collaborative memory management"
depends on PPC_SMLPAR
depends on PPC_SMLPAR && !CRASH_DUMP
default y
help
Select this option, if you want to enable the kernel interface