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DRCONF_MEM_RESERVED is a flag that represents the "Reserved Memory" status in LOPAR v2.10, section 4.2.8. If a LMB is marked as reserved, quoting LOPAR, "is not to be used or altered by the base OS". This flag is read only in the kernel, being set by the firmware/hypervisor in the DT. As an example, QEMU will set this flag in hw/ppc/spapr.c, spapr_dt_dynamic_memory(). lmb_is_removable() does not check for DRCONF_MEM_RESERVED. This function is used in dlpar_remove_lmb() as a guard before the removal logic. Since it is failing to check for !RESERVED, dlpar_remove_lmb() will fail in a later stage instead of failing in the validation when receiving a reserved LMB as input. lmb_is_removable() is also used in dlpar_memory_remove_by_count() to evaluate if we have enough LMBs to complete the request. The missing !RESERVED check in this case is causing dlpar_memory_remove_by_count() to miscalculate the number of elegible LMBs for the removal, and can make it error out later on instead of failing in the validation with the 'not enough LMBs to satisfy request' message. Making a DRCONF_MEM_RESERVED check in lmb_is_removable() fixes all these issues. Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20210512202809.95363-3-danielhb413@gmail.com
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.