[xen staging] x86/pv: disallow access to unknown MSRs

[patchbot@xxxxxxx]

commit 322ec7c89f6640ee2a99d1040b6f786cf04872cf
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Tue Sep 15 12:42:58 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Tue Sep 15 12:42:58 2020 +0200

    x86/pv: disallow access to unknown MSRs
    
    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@xxxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 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 c6fbf8f92d..d793eed401 100644
--- a/xen/arch/x86/pv/emul-priv-op.c
+++ b/xen/arch/x86/pv/emul-priv-op.c
@@ -988,9 +988,10 @@ 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;
@@ -1155,14 +1156,15 @@ 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;
     }
 
--
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