docs: kdump: Update the crashkernel description for riscv

Now "crashkernel=" parameter on riscv has been updated to support
crashkernel=X,[high,low]. Through which we can reserve memory region
above/within 32bit addressible DMA zone.

Here update the parameter description accordingly.

Signed-off-by: Chen Jiahao <chenjiahao16@huawei.com>
Reviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Acked-by: Baoquan He <bhe@redhat.com>
Link: https://lore.kernel.org/r/20230726175000.2536220-3-chenjiahao16@huawei.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index a145799..bd51974 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -862,7 +862,7 @@
                        memory region [offset, offset + size] for that kernel
                        image. If '@offset' is omitted, then a suitable offset
                        is selected automatically.
-                       [KNL, X86-64, ARM64] Select a region under 4G first, and
+                       [KNL, X86-64, ARM64, RISCV] Select a region under 4G first, and
                        fall back to reserve region above 4G when '@offset'
                        hasn't been specified.
                        See Documentation/admin-guide/kdump/kdump.rst for further details.
@@ -875,14 +875,14 @@
                        Documentation/admin-guide/kdump/kdump.rst for an example.
 
        crashkernel=size[KMG],high
-                       [KNL, X86-64, ARM64] 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.
+                       [KNL, X86-64, ARM64, RISCV] 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, ARM64] range under 4G. When crashkernel=X,high
+                       [KNL, X86-64, ARM64, RISCV] 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
@@ -893,6 +893,7 @@
                        size is platform dependent.
                          --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
                          --> arm64: 128MiB
+                         --> riscv: 128MiB
                        This one lets the user specify own low range under 4G
                        for second kernel instead.
                        0: to disable low allocation.