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[4.14,50/99] x86/mce: Fix logic and comments around MSR_PPIN_CTL

Message ID 20200319123957.111746840@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman March 19, 2020, 1:03 p.m. UTC 
From: Tony Luck <tony.luck@intel.com>

commit 59b5809655bdafb0767d3fd00a3e41711aab07e6 upstream.

There are two implemented bits in the PPIN_CTL MSR:

Bit 0: LockOut (R/WO)
      Set 1 to prevent further writes to MSR_PPIN_CTL.

Bit 1: Enable_PPIN (R/W)
       If 1, enables MSR_PPIN to be accessible using RDMSR.
       If 0, an attempt to read MSR_PPIN will cause #GP.

So there are four defined values:
	0: PPIN is disabled, PPIN_CTL may be updated
	1: PPIN is disabled. PPIN_CTL is locked against updates
	2: PPIN is enabled. PPIN_CTL may be updated
	3: PPIN is enabled. PPIN_CTL is locked against updates

Code would only enable the X86_FEATURE_INTEL_PPIN feature for case "2".
When it should have done so for both case "2" and case "3".

Fix the final test to just check for the enable bit. Also fix some of
the other comments in this function.

Fixes: 3f5a7896a509 ("x86/mce: Include the PPIN in MCE records when available")
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200226011737.9958-1-tony.luck@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/kernel/cpu/mcheck/mce_intel.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)
diff mbox series

Patch

--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -489,17 +489,18 @@  static void intel_ppin_init(struct cpuin
 			return;
 
 		if ((val & 3UL) == 1UL) {
-			/* PPIN available but disabled: */
+			/* PPIN locked in disabled mode */
 			return;
 		}
 
-		/* If PPIN is disabled, but not locked, try to enable: */
-		if (!(val & 3UL)) {
+		/* If PPIN is disabled, try to enable */
+		if (!(val & 2UL)) {
 			wrmsrl_safe(MSR_PPIN_CTL,  val | 2UL);
 			rdmsrl_safe(MSR_PPIN_CTL, &val);
 		}
 
-		if ((val & 3UL) == 2UL)
+		/* Is the enable bit set? */
+		if (val & 2UL)
 			set_cpu_cap(c, X86_FEATURE_INTEL_PPIN);
 	}
 }