linux-kernel - [PATCH v2 3/5] intel_idle: Sync up the SPEC_CTRL MSR value to x86_spec_ctrl

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Message-Id: <20230620140625.1001886-4-longman@redhat.com>
Date:   Tue, 20 Jun 2023 10:06:23 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        linux-pm@...r.kernel.org, Robin Jarry <rjarry@...hat.com>,
        Joe Mario <jmario@...hat.com>, Waiman Long <longman@...hat.com>
Subject: [PATCH v2 3/5] intel_idle: Sync up the SPEC_CTRL MSR value to x86_spec_ctrl_current

When intel_idle_ibrs() is called, it modifies the SPEC_CTRL MSR to 0
in order disable IBRS. However, the new MSR value isn't reflected in
x86_spec_ctrl_current. That will cause the new spec_ctrl_msrs debugfs
file to show incorrect result. Fix that by updating x86_spec_ctrl_current
percpu value to always match the content of the SPEC_CTRL MSR.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 drivers/idle/intel_idle.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index aa2d19db2b1d..07fa23707b3c 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -181,13 +181,17 @@ static __cpuidle int intel_idle_ibrs(struct cpuidle_device *dev,
 	u64 spec_ctrl = spec_ctrl_current();
 	int ret;
 
-	if (smt_active)
+	if (smt_active) {
+		__this_cpu_write(x86_spec_ctrl_current, 0);
 		native_wrmsrl(MSR_IA32_SPEC_CTRL, 0);
+	}
 
 	ret = __intel_idle(dev, drv, index);
 
-	if (smt_active)
+	if (smt_active) {
 		native_wrmsrl(MSR_IA32_SPEC_CTRL, spec_ctrl);
+		__this_cpu_write(x86_spec_ctrl_current, spec_ctrl);
+	}
 
 	return ret;
 }
-- 
2.31.1