1bec4adcd5
Disassembly of interrupt_enter_prepare() shows a pointless nop before the mftb c000abf0 <interrupt_enter_prepare>: c000abf0: 81 23 00 84 lwz r9,132(r3) c000abf4: 71 29 40 00 andi. r9,r9,16384 c000abf8: 41 82 00 28 beq- c000ac20 <interrupt_enter_prepare+0x30> c000abfc: ===> 60 00 00 00 nop <==== c000ac00: 7d 0c 42 e6 mftb r8 c000ac04: 80 e2 00 08 lwz r7,8(r2) c000ac08: 81 22 00 28 lwz r9,40(r2) c000ac0c: 91 02 00 24 stw r8,36(r2) c000ac10: 7d 29 38 50 subf r9,r9,r7 c000ac14: 7d 29 42 14 add r9,r9,r8 c000ac18: 91 22 00 08 stw r9,8(r2) c000ac1c: 4e 80 00 20 blr c000ac20: 60 00 00 00 nop c000ac24: 7d 5a c2 a6 mfmd_ap r10 c000ac28: 3d 20 de 00 lis r9,-8704 c000ac2c: 91 43 00 b0 stw r10,176(r3) c000ac30: 7d 3a c3 a6 mtspr 794,r9 c000ac34: 4e 80 00 20 blr That comes from the call to kuap_loc(), allthough __kuap_lock() is an empty function on the 8xx. To avoid that, only perform kuap_is_disabled() check when there is something to do with __kuap_lock(). Do the same with __kuap_save_and_lock() and __kuap_get_and_assert_locked(). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Reviewed-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/a854d25bea375d4ba6ca9c2617f9edbba397100a.1689091022.git.christophe.leroy@csgroup.eu
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.