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author | Thomas Gleixner <tglx@linutronix.de> | 2018-11-25 19:33:54 +0100 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2018-11-28 11:57:13 +0100 |
commit | 7cc765a67d8e04ef7d772425ca5a2a1e2b894c15 (patch) | |
tree | e60ac2f2ea13e3bb15f9a128585b43b9a943ca7a /arch/x86 | |
parent | 9137bb27e60e554dab694eafa4cca241fa3a694f (diff) | |
download | linux-stable-7cc765a67d8e04ef7d772425ca5a2a1e2b894c15.tar.gz linux-stable-7cc765a67d8e04ef7d772425ca5a2a1e2b894c15.tar.bz2 linux-stable-7cc765a67d8e04ef7d772425ca5a2a1e2b894c15.zip |
x86/speculation: Enable prctl mode for spectre_v2_user
Now that all prerequisites are in place:
- Add the prctl command line option
- Default the 'auto' mode to 'prctl'
- When SMT state changes, update the static key which controls the
conditional STIBP evaluation on context switch.
- At init update the static key which controls the conditional IBPB
evaluation on context switch.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Casey Schaufler <casey.schaufler@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jon Masters <jcm@redhat.com>
Cc: Waiman Long <longman9394@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Dave Stewart <david.c.stewart@intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181125185005.958421388@linutronix.de
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 41 |
1 files changed, 32 insertions, 9 deletions
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 74359fff87fd..d0137d10f9a6 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -255,11 +255,13 @@ enum spectre_v2_user_cmd { SPECTRE_V2_USER_CMD_NONE, SPECTRE_V2_USER_CMD_AUTO, SPECTRE_V2_USER_CMD_FORCE, + SPECTRE_V2_USER_CMD_PRCTL, }; static const char * const spectre_v2_user_strings[] = { [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", + [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", }; static const struct { @@ -270,6 +272,7 @@ static const struct { { "auto", SPECTRE_V2_USER_CMD_AUTO, false }, { "off", SPECTRE_V2_USER_CMD_NONE, false }, { "on", SPECTRE_V2_USER_CMD_FORCE, true }, + { "prctl", SPECTRE_V2_USER_CMD_PRCTL, false }, }; static void __init spec_v2_user_print_cond(const char *reason, bool secure) @@ -324,12 +327,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) smt_possible = false; switch (spectre_v2_parse_user_cmdline(v2_cmd)) { - case SPECTRE_V2_USER_CMD_AUTO: case SPECTRE_V2_USER_CMD_NONE: goto set_mode; case SPECTRE_V2_USER_CMD_FORCE: mode = SPECTRE_V2_USER_STRICT; break; + case SPECTRE_V2_USER_CMD_AUTO: + case SPECTRE_V2_USER_CMD_PRCTL: + mode = SPECTRE_V2_USER_PRCTL; + break; } /* Initialize Indirect Branch Prediction Barrier */ @@ -340,6 +346,9 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) case SPECTRE_V2_USER_STRICT: static_branch_enable(&switch_mm_always_ibpb); break; + case SPECTRE_V2_USER_PRCTL: + static_branch_enable(&switch_mm_cond_ibpb); + break; default: break; } @@ -352,6 +361,12 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED) return; + /* + * If SMT is not possible or STIBP is not available clear the STIPB + * mode. + */ + if (!smt_possible || !boot_cpu_has(X86_FEATURE_STIBP)) + mode = SPECTRE_V2_USER_NONE; set_mode: spectre_v2_user = mode; /* Only print the STIBP mode when SMT possible */ @@ -552,6 +567,15 @@ static void update_stibp_strict(void) on_each_cpu(update_stibp_msr, NULL, 1); } +/* Update the static key controlling the evaluation of TIF_SPEC_IB */ +static void update_indir_branch_cond(void) +{ + if (sched_smt_active()) + static_branch_enable(&switch_to_cond_stibp); + else + static_branch_disable(&switch_to_cond_stibp); +} + void arch_smt_update(void) { /* Enhanced IBRS implies STIBP. No update required. */ @@ -567,6 +591,7 @@ void arch_smt_update(void) update_stibp_strict(); break; case SPECTRE_V2_USER_PRCTL: + update_indir_branch_cond(); break; } @@ -1038,7 +1063,8 @@ static char *stibp_state(void) case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; case SPECTRE_V2_USER_PRCTL: - return ""; + if (static_key_enabled(&switch_to_cond_stibp)) + return ", STIBP: conditional"; } return ""; } @@ -1046,14 +1072,11 @@ static char *stibp_state(void) static char *ibpb_state(void) { if (boot_cpu_has(X86_FEATURE_IBPB)) { - switch (spectre_v2_user) { - case SPECTRE_V2_USER_NONE: - return ", IBPB: disabled"; - case SPECTRE_V2_USER_STRICT: + if (static_key_enabled(&switch_mm_always_ibpb)) return ", IBPB: always-on"; - case SPECTRE_V2_USER_PRCTL: - return ""; - } + if (static_key_enabled(&switch_mm_cond_ibpb)) + return ", IBPB: conditional"; + return ", IBPB: disabled"; } return ""; } |