Messages in this thread | | | From | "Lendacky, Thomas" <> | Subject | Re: General protection fault in `switch_mm_irqs_off()` | Date | Thu, 10 Jan 2019 18:34:09 +0000 |
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On 1/10/19 10:49 AM, Paul Menzel wrote: > Dear Boris, dear Thomas, > > > On 01/10/19 17:00, Borislav Petkov wrote: >> On Thu, Jan 10, 2019 at 02:57:40PM +0100, Paul Menzel wrote: >>> Thank you very much. Indeed, the machine does not crash. I used Linus’ >>> master branch for testing, and applied your patch on top. Please find >>> the full log attached. >> >>> 80.649: [ 3.197107] Spectre V2 : spectre_v2_user_select_mitigation: set X86_FEATURE_USE_IBPB >> >> This is amazing. >> >> Ok, next diff, same exercise. Thx.> >> --- >> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h >> index dad12b767ba0..528ef8336f5f 100644 >> --- a/arch/x86/include/asm/nospec-branch.h >> +++ b/arch/x86/include/asm/nospec-branch.h >> @@ -284,6 +284,12 @@ static inline void indirect_branch_prediction_barrier(void) >> { >> u64 val = PRED_CMD_IBPB; >> >> + if (WARN_ON(boot_cpu_has(X86_FEATURE_USE_IBPB))) { >> + pr_info("%s: c: %px, array: 0x%x\n", >> + __func__, &boot_cpu_data, boot_cpu_data.x86_capability[7]); >> + return; >> + } >> + >> alternative_msr_write(MSR_IA32_PRED_CMD, val, X86_FEATURE_USE_IBPB); >> } >> >> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c >> index 8654b8b0c848..e818e5abe611 100644 >> --- a/arch/x86/kernel/cpu/bugs.c >> +++ b/arch/x86/kernel/cpu/bugs.c >> @@ -371,6 +371,9 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd) >> if (boot_cpu_has(X86_FEATURE_IBPB)) { >> setup_force_cpu_cap(X86_FEATURE_USE_IBPB); >> >> + pr_err("%s: set X86_FEATURE_USE_IBPB, c: %px, array: 0x%x\n", >> + __func__, &boot_cpu_data, boot_cpu_data.x86_capability[7]); >> + >> switch (cmd) { >> case SPECTRE_V2_USER_CMD_FORCE: >> case SPECTRE_V2_USER_CMD_PRCTL_IBPB: >> diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c >> index cb28e98a0659..8566737fa500 100644 >> --- a/arch/x86/kernel/cpu/common.c >> +++ b/arch/x86/kernel/cpu/common.c >> @@ -765,6 +765,9 @@ static void apply_forced_caps(struct cpuinfo_x86 *c) >> c->x86_capability[i] &= ~cpu_caps_cleared[i]; >> c->x86_capability[i] |= cpu_caps_set[i]; >> } >> + >> + if (c == &boot_cpu_data) >> + pr_info("%s: c: %px, array: 0x%x\n", __func__, c, c->x86_capability[7]); >> } >> >> static void init_speculation_control(struct cpuinfo_x86 *c) >> @@ -778,6 +781,10 @@ static void init_speculation_control(struct cpuinfo_x86 *c) >> if (cpu_has(c, X86_FEATURE_SPEC_CTRL)) { >> set_cpu_cap(c, X86_FEATURE_IBRS); >> set_cpu_cap(c, X86_FEATURE_IBPB); >> + >> + pr_info("%s: X86_FEATURE_SPEC_CTRL: c: %px, array: 0x%x, CPUID: 0x%x\n", >> + __func__, c, c->x86_capability[7], cpuid_edx(7)); >> + >> set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL); >> } >> >> @@ -793,9 +800,13 @@ static void init_speculation_control(struct cpuinfo_x86 *c) >> set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL); >> } >> >> - if (cpu_has(c, X86_FEATURE_AMD_IBPB)) >> + if (cpu_has(c, X86_FEATURE_AMD_IBPB)) { >> set_cpu_cap(c, X86_FEATURE_IBPB); >> >> + pr_info("%s: X86_FEATURE_AMD_IBPB: c: %px, array: 0x%x, CPUID: 0x%x\n", >> + __func__, c, c->x86_capability[7], cpuid_ebx(0x80000008)); >> + } >> + >> if (cpu_has(c, X86_FEATURE_AMD_STIBP)) { >> set_cpu_cap(c, X86_FEATURE_STIBP); >> set_cpu_cap(c, X86_FEATURE_MSR_SPEC_CTRL); > > Please find the logs attached.
Ah, so the CPUID value is showing X86_FEATURE_AMD_IBPB (not sure why the cpuid command was showing a value of zero for EBX in your previous email). Let me see what I can find out about this processor/firmware relation. I wouldn't expect to see the #GP given that the firmware says IBPB is supported.
Thanks, Tom
> > > Kind regards, > > Paul >
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