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46d36b1be1
The total memory size we get in kernel is usually slightly less than the actual memory size because BIOS/firmware will reserve some memory region. So it won't export all memory as usable. E.g, on my x86_64 kvm guest with 1G memory, the total_mem value shows: UEFI boot with ovmf: 0x3faef000 Legacy boot kvm guest: 0x3ff7ec00 When specifying crashkernel=1G-2G:128M, if we have a 1G memory machine, we get total size 1023M from firmware. Then it will not fall into 1G-2G, thus no memory reserved. User will never know this, it is hard to let user know the exact total value in kernel. One way is to use dmi/smbios to get physical memory size, but it's not reliable as well. According to Prarit hardware vendors sometimes screw this up. Thus round up total size to 128M to work around this problem. This patch is a resend of [1] and rebased onto v5.19-rc2, and the original credit goes to Dave Young. [1]: http://lists.infradead.org/pipermail/kexec/2018-April/020568.html Link: https://lkml.kernel.org/r/20220627074440.187222-1-ltao@redhat.com Signed-off-by: Tao Liu <ltao@redhat.com> Acked-by: Baoquan He <bhe@redhat.com> Cc: Dave Young <dyoung@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.