[libvirt] [PATCH 1/3] qemu: Parse CPU stepping from query-cpu-model-expansion

[Jiri Denemark]

Even though only family and model are used for matching CPUID data with
CPU models from cpu_map.xml, stepping is used by x86DataFilterTSX which
is supposed to disable TSX on CPU models with broken TSX support. Thus
we need to start parsing stepping from QEMU to make sure we don't
disable TSX on CPUs which provide working TSX implementation. See the
following patch for a real world example of such CPU.

Signed-off-by: Jiri Denemark <jdenemar at redhat.com>
---
 src/cpu/cpu_x86.c            | 16 +++++++++-------
 src/cpu/cpu_x86.h            |  3 ++-
 src/qemu/qemu_capabilities.c |  5 ++++-
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/src/cpu/cpu_x86.c b/src/cpu/cpu_x86.c
index 0dbc17f199..1e82fbd943 100644
--- a/src/cpu/cpu_x86.c
+++ b/src/cpu/cpu_x86.c
@@ -531,7 +531,8 @@ virCPUx86VendorToCPUID(const char *vendor,
 
 static uint32_t
 x86MakeSignature(unsigned int family,
-                 unsigned int model)
+                 unsigned int model,
+                 unsigned int stepping)
 {
     uint32_t sig = 0;
 
@@ -551,6 +552,7 @@ x86MakeSignature(unsigned int family,
      *
      * family = eax[27:20] + eax[11:8]
      * model = eax[19:16] << 4 + eax[7:4]
+     * stepping = eax[3:0]
      */
 
     /* extFam */
@@ -570,9 +572,8 @@ x86MakeSignature(unsigned int family,
     /* Mod */
     sig |= (model & 0xf) << 4;
 
-    /* Step is irrelevant, it is used to distinguish different revisions
-     * of the same CPU model
-     */
+    /* Step */
+    sig |= stepping & 0xf;
 
     return sig;
 }
@@ -1248,7 +1249,7 @@ x86ModelParse(xmlXPathContextPtr ctxt,
             goto cleanup;
         }
 
-        model->signature = x86MakeSignature(sigFamily, sigModel);
+        model->signature = x86MakeSignature(sigFamily, sigModel, 0);
     }
 
     if (virXPathBoolean("boolean(./vendor)", ctxt)) {
@@ -2970,9 +2971,10 @@ virCPUx86DataAddCPUID(virCPUDataPtr cpuData,
 int
 virCPUx86DataSetSignature(virCPUDataPtr cpuData,
                           unsigned int family,
-                          unsigned int model)
+                          unsigned int model,
+                          unsigned int stepping)
 {
-    uint32_t signature = x86MakeSignature(family, model);
+    uint32_t signature = x86MakeSignature(family, model, stepping);
 
     return x86DataAddSignature(&cpuData->data.x86, signature);
 }
diff --git a/src/cpu/cpu_x86.h b/src/cpu/cpu_x86.h
index 91ec43fea9..5d14d83e1b 100644
--- a/src/cpu/cpu_x86.h
+++ b/src/cpu/cpu_x86.h
@@ -34,7 +34,8 @@ int virCPUx86DataAddCPUID(virCPUDataPtr cpuData,
 
 int virCPUx86DataSetSignature(virCPUDataPtr cpuData,
                               unsigned int family,
-                              unsigned int model);
+                              unsigned int model,
+                              unsigned int stepping);
 
 int virCPUx86DataSetVendor(virCPUDataPtr cpuData,
                            const char *vendor);
diff --git a/src/qemu/qemu_capabilities.c b/src/qemu/qemu_capabilities.c
index 63fb4f34e7..8e802ca44e 100644
--- a/src/qemu/qemu_capabilities.c
+++ b/src/qemu/qemu_capabilities.c
@@ -3355,6 +3355,7 @@ virQEMUCapsInitCPUModelX86(virQEMUCapsPtr qemuCaps,
     virCPUDataPtr data = NULL;
     unsigned long long sigFamily = 0;
     unsigned long long sigModel = 0;
+    unsigned long long sigStepping = 0;
     int ret = -1;
     size_t i;
 
@@ -3389,6 +3390,8 @@ virQEMUCapsInitCPUModelX86(virQEMUCapsPtr qemuCaps,
                 sigFamily = prop->value.number;
             else if (STREQ(prop->name, "model"))
                 sigModel = prop->value.number;
+            else if (STREQ(prop->name, "stepping"))
+                sigStepping = prop->value.number;
             break;
 
         case QEMU_MONITOR_CPU_PROPERTY_LAST:
@@ -3396,7 +3399,7 @@ virQEMUCapsInitCPUModelX86(virQEMUCapsPtr qemuCaps,
         }
     }
 
-    if (virCPUx86DataSetSignature(data, sigFamily, sigModel) < 0)
+    if (virCPUx86DataSetSignature(data, sigFamily, sigModel, sigStepping) < 0)
         goto cleanup;
 
     if (cpuDecode(cpu, data, virQEMUCapsGetCPUDefinitions(qemuCaps, type)) < 0)
-- 
2.14.2