x86/spectre: Add boot time option to select Spectre v2 mitigation
authorDavid Woodhouse <dwmw@amazon.co.uk>
Thu, 11 Jan 2018 21:46:26 +0000 (21:46 +0000)
committerThomas Gleixner <tglx@linutronix.de>
Thu, 11 Jan 2018 23:14:29 +0000 (00:14 +0100)
commitda285121560e769cc31797bba6422eea71d473e0
treec28344795834b8449fc63bb22c9d2a6c50edfe6c
parent76b043848fd22dbf7f8bf3a1452f8c70d557b860
x86/spectre: Add boot time option to select Spectre v2 mitigation

Add a spectre_v2= option to select the mitigation used for the indirect
branch speculation vulnerability.

Currently, the only option available is retpoline, in its various forms.
This will be expanded to cover the new IBRS/IBPB microcode features.

The RETPOLINE_AMD feature relies on a serializing LFENCE for speculation
control. For AMD hardware, only set RETPOLINE_AMD if LFENCE is a
serializing instruction, which is indicated by the LFENCE_RDTSC feature.

[ tglx: Folded back the LFENCE/AMD fixes and reworked it so IBRS
   integration becomes simple ]

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: Rik van Riel <riel@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: thomas.lendacky@amd.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Kees Cook <keescook@google.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
Cc: Paul Turner <pjt@google.com>
Link: https://lkml.kernel.org/r/1515707194-20531-5-git-send-email-dwmw@amazon.co.uk
Documentation/admin-guide/kernel-parameters.txt
arch/x86/include/asm/nospec-branch.h
arch/x86/kernel/cpu/bugs.c
arch/x86/kernel/cpu/common.c