x86/bugs: Add AMD retbleed= boot parameter
authorAlexandre Chartre <alexandre.chartre@oracle.com>
Tue, 14 Jun 2022 21:15:50 +0000 (23:15 +0200)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 23 Jul 2022 10:54:02 +0000 (12:54 +0200)
commit89eba42632fcfff30e84f66a5a7ca63882ac64ea
tree74f67041f3bbb4b08c4c31d98dcecaaa6d051c09
parent82e92fe936dbefda25ed030abe91ae76576cd6da
x86/bugs: Add AMD retbleed= boot parameter

commit 7fbf47c7ce50b38a64576b150e7011ae73d54669 upstream.

Add the "retbleed=<value>" boot parameter to select a mitigation for
RETBleed. Possible values are "off", "auto" and "unret"
(JMP2RET mitigation). The default value is "auto".

Currently, "retbleed=auto" will select the unret mitigation on
AMD and Hygon and no mitigation on Intel (JMP2RET is not effective on
Intel).

  [peterz: rebase; add hygon]
  [jpoimboe: cleanups]

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Documentation/admin-guide/kernel-parameters.txt
arch/x86/Kconfig
arch/x86/kernel/cpu/bugs.c