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When a kernel dump is present then restrict the high memory regions to avoid allocating memory where the kernel dump resides. Use the ibm,kernel-dump node under /rtas to determine whether a kernel dump exists and up to which limit GRUB can use available memory. Set the upper_mem_limit to the size of the kernel dump section of type REAL_MODE_REGION and therefore only allow GRUB's memory usage for high addresses from RMO_ADDR_MAX to upper_mem_limit. This means that GRUB can use high memory in the range of RMO_ADDR_MAX (768MB) to upper_mem_limit and the kernel-dump memory regions above upper_mem_limit remain untouched. This change has no effect on memory allocations below linux_rmo_save (typically at 640MB). Also, fall back to allocating below rmo_linux_save in case the chunk of memory there would be larger than the chunk of memory above RMO_ADDR_MAX. This can for example occur if a free memory area is found starting at 300MB extending up to 1GB but a kernel dump is located at 768MB and therefore does not allow the allocation of the high memory area but requiring to use the chunk starting at 300MB to avoid an unnecessary out-of-memory condition. Signed-off-by: Stefan Berger <stefanb@linux.ibm.com> Reviewed-by: Hari Bathini <hbathini@linux.ibm.com> Cc: Pavithra Prakash <pavrampu@in.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Carolyn Scherrer <cpscherr@us.ibm.com> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com> Cc: Sourabh Jain <sourabhjain@linux.ibm.com> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This is GRUB 2, the second version of the GRand Unified Bootloader. GRUB 2 is rewritten from scratch to make GNU GRUB cleaner, safer, more robust, more powerful, and more portable. See the file NEWS for a description of recent changes to GRUB 2. See the file INSTALL for instructions on how to build and install the GRUB 2 data and program files. See the file MAINTAINERS for information about the GRUB maintainers, etc. If you found a security vulnerability in the GRUB please check the SECURITY file to get more information how to properly report this kind of bugs to the maintainers. Please visit the official web page of GRUB 2, for more information. The URL is <http://www.gnu.org/software/grub/grub.html>. More extensive documentation is available in the Info manual, accessible using 'info grub' after building and installing GRUB 2. There are a number of important user-visible differences from the first version of GRUB, now known as GRUB Legacy. For a summary, please see: info grub Introduction 'Changes from GRUB Legacy'