[Xen-devel] [PATCH 4/4] libx86: Recalculate synthesised cpuid_policy fields when appropriate

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

When filling a policy, either from CPUID or an incomming leaf stream,
recalculate the synthesised vendor value.  All callers are expected to want
this behaviour.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
---
 xen/arch/x86/cpuid.c            |  3 ++-
 xen/include/xen/lib/x86/cpuid.h |  8 +++++---
 xen/lib/x86/cpuid.c             | 11 +++++++++++
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index b5eb584..cb170ac 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -272,7 +272,8 @@ static void __init calculate_raw_policy(void)
 
     x86_cpuid_policy_fill_native(p);
 
-    p->x86_vendor = boot_cpu_data.x86_vendor;
+    /* Nothing good will come from Xen and libx86 disagreeing on vendor. */
+    ASSERT(p->x86_vendor == boot_cpu_data.x86_vendor);
 }
 
 static void __init calculate_host_policy(void)
diff --git a/xen/include/xen/lib/x86/cpuid.h b/xen/include/xen/lib/x86/cpuid.h
index f392c78..c7a3bff 100644
--- a/xen/include/xen/lib/x86/cpuid.h
+++ b/xen/include/xen/lib/x86/cpuid.h
@@ -297,8 +297,9 @@ const uint32_t *x86_cpuid_lookup_deep_deps(uint32_t 
feature);
 /**
  * Fill a CPUID policy using the native CPUID instruction.
  *
- * No sanitisation is performed.  Values may be influenced by a hypervisor or
- * from masking/faulting configuration.
+ * No sanitisation is performed, but synthesised values are calculated.
+ * Values may be influenced by a hypervisor or from masking/faulting
+ * configuration.
  */
 void x86_cpuid_policy_fill_native(struct cpuid_policy *p);
 
@@ -339,7 +340,8 @@ int x86_cpuid_copy_to_buffer(const struct cpuid_policy 
*policy,
  * incoming leaf is out of range of cpuid_policy, in which case the optional
  * err_* pointers are filled to aid diagnostics.
  *
- * No content validation of in-range leaves is performed.
+ * No content validation of in-range leaves is performed.  Synthesised data is
+ * recalculated.
  */
 int x86_cpuid_copy_from_buffer(struct cpuid_policy *policy,
                                const cpuid_leaf_buffer_t leaves,
diff --git a/xen/lib/x86/cpuid.c b/xen/lib/x86/cpuid.c
index 104a867..311d19e 100644
--- a/xen/lib/x86/cpuid.c
+++ b/xen/lib/x86/cpuid.c
@@ -34,6 +34,13 @@ unsigned int x86_cpuid_lookup_vendor(uint32_t ebx, uint32_t 
ecx, uint32_t edx)
     return X86_VENDOR_UNKNOWN;
 }
 
+/* Recalculate the content in a CPUID policy which is derived from raw data. */
+static void recalculate_synth(struct cpuid_policy *p)
+{
+    p->x86_vendor = x86_cpuid_lookup_vendor(
+        p->basic.vendor_ebx, p->basic.vendor_ecx, p->basic.vendor_edx);
+}
+
 void x86_cpuid_policy_fill_native(struct cpuid_policy *p)
 {
     unsigned int i;
@@ -141,6 +148,8 @@ void x86_cpuid_policy_fill_native(struct cpuid_policy *p)
     for ( i = 1; i < min_t(unsigned int, ARRAY_SIZE(p->extd.raw),
                            p->extd.max_leaf + 1 - 0x80000000); ++i )
         cpuid_leaf(0x80000000 + i, &p->extd.raw[i]);
+
+    recalculate_synth(p);
 }
 
 const uint32_t *x86_cpuid_lookup_deep_deps(uint32_t feature)
@@ -363,6 +372,8 @@ int x86_cpuid_copy_from_buffer(struct cpuid_policy *p,
         }
     }
 
+    recalculate_synth(p);
+
     return 0;
 
  out_of_range:
-- 
2.1.4


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