| Message ID | 20190325135555.23768-4-juergh@canonical.com |
|---|---|
| State | New |
| Headers | show |
| Series | Spectre v2 updates | expand |
On 2019-03-25 14:55:54, Juerg Haefliger wrote: > From: Thomas Lendacky <Thomas.Lendacky@amd.com> > > Different AMD processors may have different implementations of STIBP. > When STIBP is conditionally enabled, some implementations would benefit > from having STIBP always on instead of toggling the STIBP bit through MSR > writes. This preference is advertised through a CPUID feature bit. > > When conditional STIBP support is requested at boot and the CPU advertises > STIBP always-on mode as preferred, switch to STIBP "on" support. To show > that this transition has occurred, create a new spectre_v2_user_mitigation > value and a new spectre_v2_user_strings message. The new mitigation value > is used in spectre_v2_user_select_mitigation() to print the new mitigation > message as well as to return a new string from stibp_state(). > > Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > Cc: Andrea Arcangeli <aarcange@redhat.com> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> > Cc: Jiri Kosina <jkosina@suse.cz> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Tim Chen <tim.c.chen@linux.intel.com> > Cc: David Woodhouse <dwmw@amazon.co.uk> > Link: https://lkml.kernel.org/r/20181213230352.6937.74943.stgit@tlendack-t1.amdoffice.net > > CVE-2017-5715 > > (cherry picked from commit 20c3a2c33e9fdc82e9e8e8d2a6445b3256d20191) > Signed-off-by: Juerg Haefliger <juergh@canonical.com> Acked-by: Tyler Hicks <tyhicks@canonical.com> Tyler > --- > arch/x86/include/asm/cpufeatures.h | 1 + > arch/x86/include/asm/nospec-branch.h | 1 + > arch/x86/kernel/cpu/bugs.c | 28 ++++++++++++++++++++++------ > 3 files changed, 24 insertions(+), 6 deletions(-) > > diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h > index c8ac84e90d0f..dc6e72bb45ae 100644 > --- a/arch/x86/include/asm/cpufeatures.h > +++ b/arch/x86/include/asm/cpufeatures.h > @@ -284,6 +284,7 @@ > #define X86_FEATURE_AMD_IBPB (13*32+12) /* "" Indirect Branch Prediction Barrier */ > #define X86_FEATURE_AMD_IBRS (13*32+14) /* "" Indirect Branch Restricted Speculation */ > #define X86_FEATURE_AMD_STIBP (13*32+15) /* "" Single Thread Indirect Branch Predictors */ > +#define X86_FEATURE_AMD_STIBP_ALWAYS_ON (13*32+17) /* "" Single Thread Indirect Branch Predictors always-on preferred */ > #define X86_FEATURE_AMD_SSBD (13*32+24) /* "" Speculative Store Bypass Disable */ > #define X86_FEATURE_VIRT_SSBD (13*32+25) /* Virtualized Speculative Store Bypass Disable */ > #define X86_FEATURE_AMD_SSB_NO (13*32+26) /* "" Speculative Store Bypass is fixed in hardware. */ > diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h > index 032b6009baab..dad12b767ba0 100644 > --- a/arch/x86/include/asm/nospec-branch.h > +++ b/arch/x86/include/asm/nospec-branch.h > @@ -232,6 +232,7 @@ enum spectre_v2_mitigation { > enum spectre_v2_user_mitigation { > SPECTRE_V2_USER_NONE, > SPECTRE_V2_USER_STRICT, > + SPECTRE_V2_USER_STRICT_PREFERRED, > SPECTRE_V2_USER_PRCTL, > SPECTRE_V2_USER_SECCOMP, > }; > diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c > index 3fd12053e83b..716130e08528 100644 > --- a/arch/x86/kernel/cpu/bugs.c > +++ b/arch/x86/kernel/cpu/bugs.c > @@ -262,10 +262,11 @@ enum spectre_v2_user_cmd { > }; > > 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", > - [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl", > + [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", > + [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", > + [SPECTRE_V2_USER_STRICT_PREFERRED] = "User space: Mitigation: STIBP always-on protection", > + [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", > + [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl", > }; > > static const struct { > @@ -355,6 +356,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) > break; > } > > + /* > + * At this point, an STIBP mode other than "off" has been set. > + * If STIBP support is not being forced, check if STIBP always-on > + * is preferred. > + */ > + if (mode != SPECTRE_V2_USER_STRICT && > + boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) > + mode = SPECTRE_V2_USER_STRICT_PREFERRED; > + > /* Initialize Indirect Branch Prediction Barrier */ > if (boot_cpu_has(X86_FEATURE_IBPB)) { > setup_force_cpu_cap(X86_FEATURE_USE_IBPB); > @@ -608,6 +618,7 @@ void arch_smt_update(void) > case SPECTRE_V2_USER_NONE: > break; > case SPECTRE_V2_USER_STRICT: > + case SPECTRE_V2_USER_STRICT_PREFERRED: > update_stibp_strict(); > break; > case SPECTRE_V2_USER_PRCTL: > @@ -810,7 +821,8 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) > * Indirect branch speculation is always disabled in strict > * mode. > */ > - if (spectre_v2_user == SPECTRE_V2_USER_STRICT) > + if (spectre_v2_user == SPECTRE_V2_USER_STRICT || > + spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED) > return -EPERM; > task_clear_spec_ib_disable(task); > task_update_spec_tif(task); > @@ -823,7 +835,8 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) > */ > if (spectre_v2_user == SPECTRE_V2_USER_NONE) > return -EPERM; > - if (spectre_v2_user == SPECTRE_V2_USER_STRICT) > + if (spectre_v2_user == SPECTRE_V2_USER_STRICT || > + spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED) > return 0; > task_set_spec_ib_disable(task); > if (ctrl == PR_SPEC_FORCE_DISABLE) > @@ -894,6 +907,7 @@ static int ib_prctl_get(struct task_struct *task) > return PR_SPEC_PRCTL | PR_SPEC_DISABLE; > return PR_SPEC_PRCTL | PR_SPEC_ENABLE; > case SPECTRE_V2_USER_STRICT: > + case SPECTRE_V2_USER_STRICT_PREFERRED: > return PR_SPEC_DISABLE; > default: > return PR_SPEC_NOT_AFFECTED; > @@ -1086,6 +1100,8 @@ static char *stibp_state(void) > return ", STIBP: disabled"; > case SPECTRE_V2_USER_STRICT: > return ", STIBP: forced"; > + case SPECTRE_V2_USER_STRICT_PREFERRED: > + return ", STIBP: always-on"; > case SPECTRE_V2_USER_PRCTL: > case SPECTRE_V2_USER_SECCOMP: > if (static_key_enabled(&switch_to_cond_stibp)) > -- > 2.19.1 > > > -- > kernel-team mailing list > kernel-team@lists.ubuntu.com > https://lists.ubuntu.com/mailman/listinfo/kernel-team
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index c8ac84e90d0f..dc6e72bb45ae 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -284,6 +284,7 @@ #define X86_FEATURE_AMD_IBPB (13*32+12) /* "" Indirect Branch Prediction Barrier */ #define X86_FEATURE_AMD_IBRS (13*32+14) /* "" Indirect Branch Restricted Speculation */ #define X86_FEATURE_AMD_STIBP (13*32+15) /* "" Single Thread Indirect Branch Predictors */ +#define X86_FEATURE_AMD_STIBP_ALWAYS_ON (13*32+17) /* "" Single Thread Indirect Branch Predictors always-on preferred */ #define X86_FEATURE_AMD_SSBD (13*32+24) /* "" Speculative Store Bypass Disable */ #define X86_FEATURE_VIRT_SSBD (13*32+25) /* Virtualized Speculative Store Bypass Disable */ #define X86_FEATURE_AMD_SSB_NO (13*32+26) /* "" Speculative Store Bypass is fixed in hardware. */ diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 032b6009baab..dad12b767ba0 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -232,6 +232,7 @@ enum spectre_v2_mitigation { enum spectre_v2_user_mitigation { SPECTRE_V2_USER_NONE, SPECTRE_V2_USER_STRICT, + SPECTRE_V2_USER_STRICT_PREFERRED, SPECTRE_V2_USER_PRCTL, SPECTRE_V2_USER_SECCOMP, }; diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 3fd12053e83b..716130e08528 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -262,10 +262,11 @@ enum spectre_v2_user_cmd { }; 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", - [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl", + [SPECTRE_V2_USER_NONE] = "User space: Vulnerable", + [SPECTRE_V2_USER_STRICT] = "User space: Mitigation: STIBP protection", + [SPECTRE_V2_USER_STRICT_PREFERRED] = "User space: Mitigation: STIBP always-on protection", + [SPECTRE_V2_USER_PRCTL] = "User space: Mitigation: STIBP via prctl", + [SPECTRE_V2_USER_SECCOMP] = "User space: Mitigation: STIBP via seccomp and prctl", }; static const struct { @@ -355,6 +356,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) break; } + /* + * At this point, an STIBP mode other than "off" has been set. + * If STIBP support is not being forced, check if STIBP always-on + * is preferred. + */ + if (mode != SPECTRE_V2_USER_STRICT && + boot_cpu_has(X86_FEATURE_AMD_STIBP_ALWAYS_ON)) + mode = SPECTRE_V2_USER_STRICT_PREFERRED; + /* Initialize Indirect Branch Prediction Barrier */ if (boot_cpu_has(X86_FEATURE_IBPB)) { setup_force_cpu_cap(X86_FEATURE_USE_IBPB); @@ -608,6 +618,7 @@ void arch_smt_update(void) case SPECTRE_V2_USER_NONE: break; case SPECTRE_V2_USER_STRICT: + case SPECTRE_V2_USER_STRICT_PREFERRED: update_stibp_strict(); break; case SPECTRE_V2_USER_PRCTL: @@ -810,7 +821,8 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) * Indirect branch speculation is always disabled in strict * mode. */ - if (spectre_v2_user == SPECTRE_V2_USER_STRICT) + if (spectre_v2_user == SPECTRE_V2_USER_STRICT || + spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED) return -EPERM; task_clear_spec_ib_disable(task); task_update_spec_tif(task); @@ -823,7 +835,8 @@ static int ib_prctl_set(struct task_struct *task, unsigned long ctrl) */ if (spectre_v2_user == SPECTRE_V2_USER_NONE) return -EPERM; - if (spectre_v2_user == SPECTRE_V2_USER_STRICT) + if (spectre_v2_user == SPECTRE_V2_USER_STRICT || + spectre_v2_user == SPECTRE_V2_USER_STRICT_PREFERRED) return 0; task_set_spec_ib_disable(task); if (ctrl == PR_SPEC_FORCE_DISABLE) @@ -894,6 +907,7 @@ static int ib_prctl_get(struct task_struct *task) return PR_SPEC_PRCTL | PR_SPEC_DISABLE; return PR_SPEC_PRCTL | PR_SPEC_ENABLE; case SPECTRE_V2_USER_STRICT: + case SPECTRE_V2_USER_STRICT_PREFERRED: return PR_SPEC_DISABLE; default: return PR_SPEC_NOT_AFFECTED; @@ -1086,6 +1100,8 @@ static char *stibp_state(void) return ", STIBP: disabled"; case SPECTRE_V2_USER_STRICT: return ", STIBP: forced"; + case SPECTRE_V2_USER_STRICT_PREFERRED: + return ", STIBP: always-on"; case SPECTRE_V2_USER_PRCTL: case SPECTRE_V2_USER_SECCOMP: if (static_key_enabled(&switch_to_cond_stibp))