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x86/bugs: Add AMD retbleed= boot parameter

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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>
This commit is contained in:
Alexandre Chartre
2022-06-14 23:15:50 +02:00
committed by Greg Kroah-Hartman
parent 82e92fe936
commit 89eba42632
3 changed files with 125 additions and 1 deletions
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15
Documentation/admin-guide/kernel-parameters.txt
View File

@@ -4968,6 +4968,21 @@
retain_initrd [RAM] Keep initrd memory after extraction
retbleed= [X86] Control mitigation of RETBleed (Arbitrary
Speculative Code Execution with Return Instructions)
vulnerability.
off - unconditionally disable
auto - automatically select a migitation
unret - force enable untrained return thunks,
only effective on AMD Zen {1,2}
based systems.
Selecting 'auto' will choose a mitigation method at run
time according to the CPU.
Not specifying this option is equivalent to retbleed=auto.
rfkill.default_state=
0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
etc. communication is blocked by default.