From: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com> Signed-off-by: Mahesh Salgaonkar <mah...@linux.vnet.ibm.com> --- Documentation/powerpc/firmware-assisted-dump.txt | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/Documentation/powerpc/firmware-assisted-dump.txt b/Documentation/powerpc/firmware-assisted-dump.txt index 30b32f879219..2ab13270b050 100644 --- a/Documentation/powerpc/firmware-assisted-dump.txt +++ b/Documentation/powerpc/firmware-assisted-dump.txt @@ -113,7 +113,15 @@ header, is usually reserved at an offset greater than boot memory size (see Fig. 1). This area is *not* released: this region will be kept permanently reserved, so that it can act as a receptacle for a copy of the boot memory content in addition to CPU state -and HPTE region, in the case a crash does occur. +and HPTE region, in the case a crash does occur. Since this reserved +memory area is used only after the system crash, there is no point in +blocking this significant chunk of memory from production kernel. +Hence, the implementation uses the Linux kernel's Contiguous Memory +Allocator (CMA) for memory reservation. With CMA reservation this memory +will be available for applications to use it, while kernel is prevented +from using it. With this fadump will still be able to capture all of +the kernel memory and most of the user space memory except the user +pages that were present in CMA region. The first kernel, during fadump registration, prepares ELF core header that contains necessary information for the coredump of the 1st kernel
