x86, kdump: Change crashkernel_high/low= to crashkernel=,high/low

[mirror_ubuntu-artful-kernel.git] / Documentation / kernel-parameters.txt

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81dbc37fc2dbfa005ff607890df3a8bbc6b..a1ac1f1d6d3413386f771afbff0404d381d2e57d 100644 (file)
--- 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>