From: Borislav Petkov <bp@alien8.de>
To: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Thomas Lendacky <Thomas.Lendacky@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jiri Kosina <jikos@kernel.org>, "x86@kernel.org" <x86@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Tim Chen <tim.c.chen@linux.intel.com>
Subject: Re: General protection fault in `switch_mm_irqs_off()`
Date: Wed, 9 Jan 2019 22:11:04 +0100 [thread overview]
Message-ID: <20190109211104.GG15665@zn.tnic> (raw)
In-Reply-To: <9bca3e26-1dfc-6e86-cf28-90cadd983ff4@molgen.mpg.de>
On Wed, Jan 09, 2019 at 05:34:11PM +0100, Paul Menzel wrote:
> Is there a way to trace the value of `boot_cpu_data` from
> `arch/x86/include/asm/cpufeature.h` with some Linux Kernel magic?
>
> #define boot_cpu_has(bit) cpu_has(&boot_cpu_data, bit)
>
> Or is rebuilding with print statements the only solution?
Yes. Just apply this and catch output. It is a wild guess anyway as
this whole deal looks really strange but at least it should not #GP the
machine.
---
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index dad12b767ba0..ec4688779900 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -284,6 +284,9 @@ static inline void indirect_branch_prediction_barrier(void)
{
u64 val = PRED_CMD_IBPB;
+ if (WARN_ON(boot_cpu_has(X86_FEATURE_USE_IBPB)))
+ 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 1de0f4170178..4ed4cc99a2c0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -371,6 +371,8 @@ 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\n", __func__);
+
switch (cmd) {
case SPECTRE_V2_USER_CMD_FORCE:
case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2019-01-09 21:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-03 21:45 General protection fault in `switch_mm_irqs_off()` Paul Menzel
2019-01-04 12:41 ` Paul Menzel
2019-01-04 15:47 ` Borislav Petkov
2019-01-04 17:32 ` Lendacky, Thomas
2019-01-04 16:42 ` Jiri Kosina
[not found] ` <cb7ba667-562b-1e4c-f16e-7c11804bc98a@molgen.mpg.de>
2019-01-09 13:16 ` Thomas Gleixner
2019-01-09 13:35 ` Paul Menzel
2019-01-09 14:29 ` Lendacky, Thomas
2019-01-09 14:34 ` Paul Menzel
2019-01-09 16:15 ` Lendacky, Thomas
2019-01-09 16:34 ` Paul Menzel
2019-01-09 21:11 ` Borislav Petkov [this message]
[not found] ` <9bbcbaa7-b164-fcef-0588-7c5f25aa2440@molgen.mpg.de>
2019-01-10 15:53 ` Lendacky, Thomas
2019-01-10 16:02 ` Borislav Petkov
2019-01-10 16:00 ` Borislav Petkov
2019-01-10 16:49 ` Paul Menzel
2019-01-10 18:34 ` Lendacky, Thomas
2019-01-14 17:00 ` Lendacky, Thomas
2019-01-14 17:09 ` Paul Menzel
2019-01-14 17:37 ` Lendacky, Thomas
2019-10-02 15:52 ` Paul Menzel
2019-01-09 13:19 ` Paul Menzel
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