x86/MCA: suppress bank clearing for certain injected events

As the bits indicating validity of the ADDR and MISC bank MSRs may be
injected in a way that isn't consistent with what the underlying
hardware implements (while the bank must be valid for injection to
work, the auxiliary MSRs may not be implemented - and hence cause #GP
upon access - if the hardware never sets the corresponding valid bits.

Consequently we need to do the clearing writes only if no value was
interposed for the respective MSR (which also makes sense the other way
around: there's no point in clearing a hardware register when all data
read came from software). Of course this all requires the injection
tool to do things in a consistent way (but that had been a requirement
before already).

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Ren Yongjie <yongjie.ren@intel.com>
Acked-by: Liu Jinsong <jinsong.liu@intel.com>

2 files changed, 11 insertions, 9 deletions

diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
index ced1a89f4f..fa879821fe 100644
--- a/xen/arch/x86/cpu/mcheck/mce.c
+++ b/xen/arch/x86/cpu/mcheck/mce.c
@@ -1065,13 +1065,15 @@ static void intpose_add(unsigned int cpu_nr, uint64_t msr, uint64_t val)
     printk("intpose_add: interpose array full - request dropped\n");
 }
 
-void intpose_inval(unsigned int cpu_nr, uint64_t msr)
+bool_t intpose_inval(unsigned int cpu_nr, uint64_t msr)
 {
-    struct intpose_ent *ent;
+    struct intpose_ent *ent = intpose_lookup(cpu_nr, msr, NULL);
 
-    if ((ent = intpose_lookup(cpu_nr, msr, NULL)) != NULL) {
-        ent->cpu_nr = -1;
-    }
+    if ( !ent )
+        return 0;
+
+    ent->cpu_nr = -1;
+    return 1;
 }
 
 #define IS_MCA_BANKREG(r) \
diff --git a/xen/arch/x86/cpu/mcheck/mce.h b/xen/arch/x86/cpu/mcheck/mce.h
index 6006fb4b7e..cbd123d555 100644
--- a/xen/arch/x86/cpu/mcheck/mce.h
+++ b/xen/arch/x86/cpu/mcheck/mce.h
@@ -77,7 +77,7 @@ extern void mce_recoverable_register(mce_recoverable_t);
 /* Read an MSR, checking for an interposed value first */
 extern struct intpose_ent *intpose_lookup(unsigned int, uint64_t,
     uint64_t *);
-extern void intpose_inval(unsigned int, uint64_t);
+extern bool_t intpose_inval(unsigned int, uint64_t);
 
 static inline uint64_t mca_rdmsr(unsigned int msr)
 {
@@ -89,9 +89,9 @@ static inline uint64_t mca_rdmsr(unsigned int msr)
 
 /* Write an MSR, invalidating any interposed value */
 #define mca_wrmsr(msr, val) do { \
-       intpose_inval(smp_processor_id(), msr); \
-       wrmsrl(msr, val); \
-} while (0)
+    if ( !intpose_inval(smp_processor_id(), msr) ) \
+        wrmsrl(msr, val); \
+} while ( 0 )
 
 
 /* Utility function to "logout" all architectural MCA telemetry from the MCA