[PATCH v4 3/5] x86/pv: disallow access to unknown MSRs

[Roger Pau Monne <roger.pau@citrix.com>]

Change the catch-all behavior for MSR not explicitly handled. Instead
of allow full read-access to the MSR space and silently dropping
writes return an exception when the MSR is not explicitly handled.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
Changes since v2:
 - Added missing 0x prefix.
---
 xen/arch/x86/pv/emul-priv-op.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/xen/arch/x86/pv/emul-priv-op.c b/xen/arch/x86/pv/emul-priv-op.c
index bcc1188f6a..2d9953f5b4 100644
--- a/xen/arch/x86/pv/emul-priv-op.c
+++ b/xen/arch/x86/pv/emul-priv-op.c
@@ -972,9 +972,10 @@ static int read_msr(unsigned int reg, uint64_t *val,
         }
         /* fall through */
     default:
+        gdprintk(XENLOG_WARNING, "RDMSR 0x%08x unimplemented\n", reg);
+        break;
+
     normal:
-        /* Everyone can read the MSR space. */
-        /* gdprintk(XENLOG_WARNING, "Domain attempted RDMSR %08x\n", reg); */
         if ( rdmsr_safe(reg, *val) )
             break;
         return X86EMUL_OKAY;
@@ -1141,14 +1142,15 @@ static int write_msr(unsigned int reg, uint64_t val,
         }
         /* fall through */
     default:
-        if ( rdmsr_safe(reg, temp) )
-            break;
+        gdprintk(XENLOG_WARNING,
+                 "WRMSR 0x%08x val 0x%016"PRIx64" unimplemented\n",
+                 reg, val);
+        break;
 
-        if ( val != temp )
     invalid:
-            gdprintk(XENLOG_WARNING,
-                     "Domain attempted WRMSR %08x from 0x%016"PRIx64" to 0x%016"PRIx64"\n",
-                     reg, temp, val);
+        gdprintk(XENLOG_WARNING,
+                 "Domain attempted WRMSR 0x%08x from 0x%016"PRIx64" to 0x%016"PRIx64"\n",
+                 reg, temp, val);
         return X86EMUL_OKAY;
     }
 
-- 
2.28.0