Merge branch 'x86-kdump-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull kdump fixes from Peter Anvin:
 "The kexec/kdump people have found several problems with the support
  for loading over 4 GiB that was introduced in this merge cycle.  This
  is partly due to a number of design problems inherent in the way the
  various pieces of kdump fit together (it is pretty horrifically manual
  in many places.)

  After a *lot* of iterations this is the patchset that was agreed upon,
  but of course it is now very late in the cycle.  However, because it
  changes both the syntax and semantics of the crashkernel option, it
  would be desirable to avoid a stable release with the broken
  interfaces."

I'm not happy with the timing, since originally the plan was to release
the final 3.9 tomorrow.  But apparently I'm doing an -rc8 instead...

* 'x86-kdump-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  kexec: use Crash kernel for Crash kernel low
  x86, kdump: Change crashkernel_high/low= to crashkernel=,high/low
  x86, kdump: Retore crashkernel= to allocate under 896M
  x86, kdump: Set crashkernel_low automatically

1 files changed, 20 insertions, 3 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index d1cc3a9fa14f..8ccbf27aead4 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -596,9 +596,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         is selected automatically. Check
                         Documentation/kdump/kdump.txt for further details.
 
-        crashkernel_low=size[KMG]
-                        [KNL, x86] parts under 4G.
-
         crashkernel=range1:size1[,range2:size2,...][@offset]
                         [KNL] Same as above, but depends on the memory
                         in the running system. The syntax of range is
@@ -606,6 +603,26 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         a memory unit (amount[KMG]). See also
                         Documentation/kdump/kdump.txt for an example.
 
+        crashkernel=size[KMG],high
+                        [KNL, x86_64] range could be above 4G. Allow kernel
+                        to allocate physical memory region from top, so could
+                        be above 4G if system have more than 4G ram installed.
+                        Otherwise memory region will be allocated below 4G, if
+                        available.
+                        It will be ignored if crashkernel=X is specified.
+        crashkernel=size[KMG],low
+                        [KNL, x86_64] range under 4G. When crashkernel=X,high
+                        is passed, kernel could allocate physical memory region
+                        above 4G, that cause second kernel crash on system
+                        that require some amount of low memory, e.g. swiotlb
+                        requires at least 64M+32K low memory.  Kernel would
+                        try to allocate 72M below 4G automatically.
+                        This one let user to specify own low range under 4G
+                        for second kernel instead.
+                        0: to disable low allocation.
+                        It will be ignored when crashkernel=X,high is not used
+                        or memory reserved is below 4G.
+
         cs89x0_dma=     [HW,NET]
                         Format: <dma>