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early_reserve_e820() is an early hack for kexec that does a limited fixup of the mptable and passes it to the kexec kernel as if it was the real thing. For this it needs to allocate memory - but no memory allocator is available yet beyond the memblock allocator, so early_reserve_e820() is really a wrapper around memblock_alloc() plus a hack to update the e820_table_firmware entries. The name 'reserve' is really a bit of a misnomer, as 'reserved' memory typically means memory completely inaccessible to the kernel - while here what we want to do is a special RAM allocation for our own purposes and insert that as RAM_RESERVED. Rename the function to e820__memblock_alloc_reserved() to better signal this dual purpose, plus document it better, which was omitted when it was merged. The barely comprehensible and cryptic comment: /* * pre allocated 4k and reserved it in memblock and e820_table_firmware */ u64 __init e820__memblock_alloc_reserved(u64 size, u64 align) ... does not count as documentation, replace it with: /* * Allocate the requested number of bytes with the requsted alignment * and return (the physical address) to the caller. Also register this * range in the 'firmware' E820 table. * * This allows kexec to fake a new mptable, as if it came from the real * system. */ u64 __init e820__memblock_alloc_reserved(u64 size, u64 align) No change in functionality. Cc: Alex Thorlton <athorlton@sgi.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Huang, Ying <ying.huang@intel.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Juergen Gross <jgross@suse.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paul Jackson <pj@sgi.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Rafael J. Wysocki <rjw@sisk.pl> Cc: Tejun Heo <tj@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Wei Yang <richard.weiyang@gmail.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: linux-kernel@vger.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.