x86/mce: fix logic and comments around MSR_PPIN_CTL

There are two implemented bits in the PPIN_CTL MSR:

Bit0: 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.

Signed-off-by: Tony Luck <tony.luck@intel.com>
[Linux commit ???]

One of the adjusted comments doesn't exist in our code, and I disagree
with the adjustment to the other one and its associate code change: I
don't think there's a point trying to enable PPIN if the locked bit is
set. Hence it's just the main code change that gets pulled in, plus it
gets cloned to the AMD side.

Requested-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

diff --git a/xen/arch/x86/cpu/mcheck/mce_amd.c b/xen/arch/x86/cpu/mcheck/mce_amd.c
index 5873511f5ef6cb869b10adfa7cfa65c3a869d392..787ce961b68607217ca00f316a984a95ea559076 100644 (file)
--- a/xen/arch/x86/cpu/mcheck/mce_amd.c
+++ b/xen/arch/x86/cpu/mcheck/mce_amd.c
@@ -329,7 +329,7 @@ amd_mcheck_init(struct cpuinfo_x86 *ci)
             rdmsrl(MSR_AMD_PPIN_CTL, val);
         }
 
-        if ( (val & (PPIN_ENABLE | PPIN_LOCKOUT)) != PPIN_ENABLE )
+        if ( !(val & PPIN_ENABLE) )
             ppin_msr = 0;
         else if ( ci == &boot_cpu_data )
             ppin_msr = MSR_AMD_PPIN;

diff --git a/xen/arch/x86/cpu/mcheck/mce_intel.c b/xen/arch/x86/cpu/mcheck/mce_intel.c
index 29b9983172fda11c477d65844dc15b9b200e2007..bb9f3a3ff795499ec79db5f25ed7c76295cb2299 100644 (file)
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -885,7 +885,7 @@ static void intel_init_ppin(const struct cpuinfo_x86 *c)
             rdmsr_safe(MSR_PPIN_CTL, val);
         }
 
-        if ( (val & (PPIN_ENABLE | PPIN_LOCKOUT)) != PPIN_ENABLE )
+        if ( !(val & PPIN_ENABLE) )
             ppin_msr = 0;
         else if ( c == &boot_cpu_data )
             ppin_msr = MSR_PPIN;