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[Xen-devel] [PATCH v2 4/6] x86/viridian: add warnings for unimplemented hypercalls and MSRs



These warnings can be useful when Microsoft updates Windows.

In the past there have been several cases when Windows erroneously uses
hypercalls and MSRs that should be gated on CPUID flags than Xen does
not set. The usual symptom is a guest crash with little or no information
in the hypervisor log. Adding these warnings at least gives a clue as to
what might be happening in such cases.

Some versions of Windows do currently issue hypercalls that they should
not, so this patch whitelists those to avoid the warnings as the lack
of implementation is clearly proved not to be a problem to the guest.

The warnings are rate limited so a malicious guest cannot use them to
as a DoS.

NOTE: Because the MSR warnings need to be gated on range checking the
      MSR address this patch imports the up-to-date definitions of all
      the viridian MSRs from the specification.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

v2:
 - Use gprintk() rather than gdprintk()
 - Further changes requested by Jan
---
 xen/arch/x86/hvm/viridian.c | 106 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 92 insertions(+), 14 deletions(-)

diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index 27ad5e8..d241de2 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -23,17 +23,73 @@
 #include <public/hvm/hvm_op.h>
 
 /* Viridian MSR numbers. */
-#define HV_X64_MSR_GUEST_OS_ID                  0x40000000
-#define HV_X64_MSR_HYPERCALL                    0x40000001
-#define HV_X64_MSR_VP_INDEX                     0x40000002
-#define HV_X64_MSR_TIME_REF_COUNT               0x40000020
-#define HV_X64_MSR_REFERENCE_TSC                0x40000021
-#define HV_X64_MSR_TSC_FREQUENCY                0x40000022
-#define HV_X64_MSR_APIC_FREQUENCY               0x40000023
-#define HV_X64_MSR_EOI                          0x40000070
-#define HV_X64_MSR_ICR                          0x40000071
-#define HV_X64_MSR_TPR                          0x40000072
-#define HV_X64_MSR_VP_ASSIST_PAGE               0x40000073
+#define HV_X64_MSR_GUEST_OS_ID                   0x40000000
+#define HV_X64_MSR_HYPERCALL                     0x40000001
+#define HV_X64_MSR_VP_INDEX                      0x40000002
+#define HV_X64_MSR_RESET                         0x40000003
+#define HV_X64_MSR_VP_RUNTIME                    0x40000010
+#define HV_X64_MSR_TIME_REF_COUNT                0x40000020
+#define HV_X64_MSR_REFERENCE_TSC                 0x40000021
+#define HV_X64_MSR_TSC_FREQUENCY                 0x40000022
+#define HV_X64_MSR_APIC_FREQUENCY                0x40000023
+#define HV_X64_MSR_EOI                           0x40000070
+#define HV_X64_MSR_ICR                           0x40000071
+#define HV_X64_MSR_TPR                           0x40000072
+#define HV_X64_MSR_VP_ASSIST_PAGE                0x40000073
+#define HV_X64_MSR_SCONTROL                      0x40000080
+#define HV_X64_MSR_SVERSION                      0x40000081
+#define HV_X64_MSR_SIEFP                         0x40000082
+#define HV_X64_MSR_SIMP                          0x40000083
+#define HV_X64_MSR_EOM                           0x40000084
+#define HV_X64_MSR_SINT0                         0x40000090
+#define HV_X64_MSR_SINT1                         0x40000091
+#define HV_X64_MSR_SINT2                         0x40000092
+#define HV_X64_MSR_SINT3                         0x40000093
+#define HV_X64_MSR_SINT4                         0x40000094
+#define HV_X64_MSR_SINT5                         0x40000095
+#define HV_X64_MSR_SINT6                         0x40000096
+#define HV_X64_MSR_SINT7                         0x40000097
+#define HV_X64_MSR_SINT8                         0x40000098
+#define HV_X64_MSR_SINT9                         0x40000099
+#define HV_X64_MSR_SINT10                        0x4000009A
+#define HV_X64_MSR_SINT11                        0x4000009B
+#define HV_X64_MSR_SINT12                        0x4000009C
+#define HV_X64_MSR_SINT13                        0x4000009D
+#define HV_X64_MSR_SINT14                        0x4000009E
+#define HV_X64_MSR_SINT15                        0x4000009F
+#define HV_X64_MSR_STIMER0_CONFIG                0x400000B0
+#define HV_X64_MSR_STIMER0_COUNT                 0x400000B1
+#define HV_X64_MSR_STIMER1_CONFIG                0x400000B2
+#define HV_X64_MSR_STIMER1_COUNT                 0x400000B3
+#define HV_X64_MSR_STIMER2_CONFIG                0x400000B4
+#define HV_X64_MSR_STIMER2_COUNT                 0x400000B5
+#define HV_X64_MSR_STIMER3_CONFIG                0x400000B6
+#define HV_X64_MSR_STIMER3_COUNT                 0x400000B7
+#define HV_X64_MSR_POWER_STATE_TRIGGER_C1        0x400000C1
+#define HV_X64_MSR_POWER_STATE_TRIGGER_C2        0x400000C2
+#define HV_X64_MSR_POWER_STATE_TRIGGER_C3        0x400000C3
+#define HV_X64_MSR_POWER_STATE_CONFIG_C1         0x400000D1
+#define HV_X64_MSR_POWER_STATE_CONFIG_C2         0x400000D2
+#define HV_X64_MSR_POWER_STATE_CONFIG_C3         0x400000D3
+#define HV_X64_MSR_STATS_PARTITION_RETAIL_PAGE   0x400000E0
+#define HV_X64_MSR_STATS_PARTITION_INTERNAL_PAGE 0x400000E1
+#define HV_X64_MSR_STATS_VP_RETAIL_PAGE          0x400000E2
+#define HV_X64_MSR_STATS_VP_INTERNAL_PAGE        0x400000E3
+#define HV_X64_MSR_GUEST_IDLE                    0x400000F0
+#define HV_X64_MSR_SYNTH_DEBUG_CONTROL           0x400000F1
+#define HV_X64_MSR_SYNTH_DEBUG_STATUS            0x400000F2
+#define HV_X64_MSR_SYNTH_DEBUG_SEND_BUFFER       0x400000F3
+#define HV_X64_MSR_SYNTH_DEBUG_RECEIVE_BUFFER    0x400000F4
+#define HV_X64_MSR_SYNTH_DEBUG_PENDING_BUFFER    0x400000F5
+#define HV_X64_MSR_CRASH_P0                      0x40000100
+#define HV_X64_MSR_CRASH_P1                      0x40000101
+#define HV_X64_MSR_CRASH_P2                      0x40000102
+#define HV_X64_MSR_CRASH_P3                      0x40000103
+#define HV_X64_MSR_CRASH_P4                      0x40000104
+#define HV_X64_MSR_CRASH_CTL                     0x40000105
+
+#define VIRIDIAN_MSR_MIN HV_X64_MSR_GUEST_OS_ID
+#define VIRIDIAN_MSR_MAX HV_X64_MSR_CRASH_CTL
 
 /* Viridian Hypercall Status Codes. */
 #define HV_STATUS_SUCCESS                       0x0000
@@ -41,9 +97,11 @@
 #define HV_STATUS_INVALID_PARAMETER             0x0005
 
 /* Viridian Hypercall Codes. */
-#define HvFlushVirtualAddressSpace 2
-#define HvFlushVirtualAddressList  3
-#define HvNotifyLongSpinWait       8
+#define HvFlushVirtualAddressSpace 0x0002
+#define HvFlushVirtualAddressList  0x0003
+#define HvNotifyLongSpinWait       0x0008
+#define HvGetPartitionId           0x0046
+#define HvExtCallQueryCapabilities 0x8001
 
 /* Viridian Hypercall Flags. */
 #define HV_FLUSH_ALL_PROCESSORS 1
@@ -552,6 +610,10 @@ int wrmsr_viridian_regs(uint32_t idx, uint64_t val)
         break;
 
     default:
+        if ( idx >= VIRIDIAN_MSR_MIN && idx <= VIRIDIAN_MSR_MAX )
+            gprintk(XENLOG_WARNING, "write to unimplemented MSR %08x\n",
+                    idx);
+
         return 0;
     }
 
@@ -675,6 +737,10 @@ int rdmsr_viridian_regs(uint32_t idx, uint64_t *val)
     }
 
     default:
+        if ( idx >= VIRIDIAN_MSR_MIN && idx <= VIRIDIAN_MSR_MAX )
+            gprintk(XENLOG_WARNING, "read from unimplemented MSR %08x\n",
+                    idx);
+
         return 0;
     }
 
@@ -828,6 +894,18 @@ int viridian_hypercall(struct cpu_user_regs *regs)
     }
 
     default:
+        gprintk(XENLOG_WARNING, "unimplemented hypercall %04x\n",
+                input.call_code);
+
+    case HvGetPartitionId:
+    case HvExtCallQueryCapabilities:
+        /*
+         * These hypercalls seem to be erroneously issued by Windows
+         * despite neither AccessPartitionId nor EnableExtendedHypercalls
+         * being set in CPUID leaf 2.
+         * Given that return a status of 'invalid code' has not so far
+         * caused any problems it's not worth logging.
+         */
         status = HV_STATUS_INVALID_HYPERCALL_CODE;
         break;
     }
-- 
2.1.4


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