linux-kernel - [PATCH] x86/mce/therm_throt: Avoid updating RO and reserved bits

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Message-Id: <20191128150824.22413-1-srinivas.pandruvada@linux.intel.com>
Date:   Thu, 28 Nov 2019 07:08:24 -0800
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     linux@...inikbrodowski.net, tony.luck@...el.com, bp@...en8.de,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com
Cc:     x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Subject: [PATCH] x86/mce/therm_throt: Avoid updating RO and reserved bits

While writing to MSR IA32_THERM_STATUS/IA32_PKG_THERM_STATUS, avoid
writing 1 to read only and reserved fields. Updating some fields
generates exception.

Fixes: f6656208f04e ("x86/mce/therm_throt: Optimize notifications of thermal throttle")
Reported-by: Dominik Brodowski <linux@...inikbrodowski.net>
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
---
 arch/x86/kernel/cpu/mce/therm_throt.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/therm_throt.c b/arch/x86/kernel/cpu/mce/therm_throt.c
index d01e0da0163a..80be4a5ac303 100644
--- a/arch/x86/kernel/cpu/mce/therm_throt.c
+++ b/arch/x86/kernel/cpu/mce/therm_throt.c
@@ -195,17 +195,24 @@ static const struct attribute_group thermal_attr_group = {
 #define THERM_THROT_POLL_INTERVAL	HZ
 #define THERM_STATUS_PROCHOT_LOG	BIT(1)
 
+#define THERM_STATUS_CLEAR_CORE_MASK (BIT(1) | BIT(3) | BIT(5) | BIT(7) | BIT(9) | BIT(11) | BIT(13) | BIT(15))
+#define THERM_STATUS_CLEAR_PKG_MASK (BIT(1) | BIT(3) | BIT(5) | BIT(7) | BIT(9) | BIT(11))
+
 static void clear_therm_status_log(int level)
 {
 	int msr;
-	u64 msr_val;
+	u64 mask, msr_val;
 
-	if (level == CORE_LEVEL)
+	if (level == CORE_LEVEL) {
 		msr = MSR_IA32_THERM_STATUS;
-	else
+		mask = THERM_STATUS_CLEAR_CORE_MASK;
+	} else {
 		msr = MSR_IA32_PACKAGE_THERM_STATUS;
+		mask = THERM_STATUS_CLEAR_PKG_MASK;
+	}
 
 	rdmsrl(msr, msr_val);
+	msr_val &= mask;
 	wrmsrl(msr, msr_val & ~THERM_STATUS_PROCHOT_LOG);
 }
 
-- 
2.17.2