[Qemu-devel] [PATCH][STABLE] kvm: Fix cpuid initialization

[Jan Kiszka]

[ Looks like we need more kvm users via upstream qemu... ]

Fix (more or less) spurious guest boot failures due to corrupted cpuid
states. The reason was insufficient initialization of cpuid entries
before passing them to the kernel.

At this chance also fix improper entry pointer progression and simplify
the code a bit.

Signed-off-by: Jan Kiszka <address@hidden>
---

 target-i386/kvm.c |   60 ++++++++++++++++++-----------------------------------
 1 files changed, 20 insertions(+), 40 deletions(-)

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 4f437c2..2de8b81 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -41,12 +41,11 @@ int kvm_arch_init_vcpu(CPUState *env)
         struct kvm_cpuid_entry2 entries[100];
     } __attribute__((packed)) cpuid_data;
     uint32_t limit, i, j, cpuid_i;
-    uint32_t eax, ebx, ecx, edx;
+    uint32_t unused;
 
     cpuid_i = 0;
 
-    cpu_x86_cpuid(env, 0, 0, &eax, &ebx, &ecx, &edx);
-    limit = eax;
+    cpu_x86_cpuid(env, 0, 0, &limit, &unused, &unused, &unused);
 
     for (i = 0; i <= limit; i++) {
         struct kvm_cpuid_entry2 *c = &cpuid_data.entries[cpuid_i++];
@@ -56,26 +55,17 @@ int kvm_arch_init_vcpu(CPUState *env)
             /* Keep reading function 2 till all the input is received */
             int times;
 
-            cpu_x86_cpuid(env, i, 0, &eax, &ebx, &ecx, &edx);
-            times = eax & 0xff;
-
             c->function = i;
-            c->flags |= KVM_CPUID_FLAG_STATEFUL_FUNC;
-            c->flags |= KVM_CPUID_FLAG_STATE_READ_NEXT;
-            c->eax = eax;
-            c->ebx = ebx;
-            c->ecx = ecx;
-            c->edx = edx;
+            c->flags = KVM_CPUID_FLAG_STATEFUL_FUNC |
+                       KVM_CPUID_FLAG_STATE_READ_NEXT;
+            cpu_x86_cpuid(env, i, 0, &c->eax, &c->ebx, &c->ecx, &c->edx);
+            times = c->eax & 0xff;
 
             for (j = 1; j < times; ++j) {
-                cpu_x86_cpuid(env, i, 0, &eax, &ebx, &ecx, &edx);
+                c = &cpuid_data.entries[cpuid_i++];
                 c->function = i;
-                c->flags |= KVM_CPUID_FLAG_STATEFUL_FUNC;
-                c->eax = eax;
-                c->ebx = ebx;
-                c->ecx = ecx;
-                c->edx = edx;
-                c = &cpuid_data.entries[++cpuid_i];
+                c->flags = KVM_CPUID_FLAG_STATEFUL_FUNC;
+                cpu_x86_cpuid(env, i, 0, &c->eax, &c->ebx, &c->ecx, &c->edx);
             }
             break;
         }
@@ -83,46 +73,36 @@ int kvm_arch_init_vcpu(CPUState *env)
         case 0xb:
         case 0xd:
             for (j = 0; ; j++) {
-                cpu_x86_cpuid(env, i, j, &eax, &ebx, &ecx, &edx);
                 c->function = i;
                 c->flags = KVM_CPUID_FLAG_SIGNIFCANT_INDEX;
                 c->index = j;
-                c->eax = eax;
-                c->ebx = ebx;
-                c->ecx = ecx;
-                c->edx = edx;
-                c = &cpuid_data.entries[++cpuid_i];
+                cpu_x86_cpuid(env, i, j, &c->eax, &c->ebx, &c->ecx, &c->edx);
 
-                if (i == 4 && eax == 0)
+                if (i == 4 && c->eax == 0)
                     break;
-                if (i == 0xb && !(ecx & 0xff00))
+                if (i == 0xb && !(c->ecx & 0xff00))
                     break;
-                if (i == 0xd && eax == 0)
+                if (i == 0xd && c->eax == 0)
                     break;
+
+                c = &cpuid_data.entries[cpuid_i++];
             }
             break;
         default:
-            cpu_x86_cpuid(env, i, 0, &eax, &ebx, &ecx, &edx);
             c->function = i;
-            c->eax = eax;
-            c->ebx = ebx;
-            c->ecx = ecx;
-            c->edx = edx;
+            c->flags = 0;
+            cpu_x86_cpuid(env, i, 0, &c->eax, &c->ebx, &c->ecx, &c->edx);
             break;
         }
     }
-    cpu_x86_cpuid(env, 0x80000000, 0, &eax, &ebx, &ecx, &edx);
-    limit = eax;
+    cpu_x86_cpuid(env, 0x80000000, 0, &limit, &unused, &unused, &unused);
 
     for (i = 0x80000000; i <= limit; i++) {
         struct kvm_cpuid_entry2 *c = &cpuid_data.entries[cpuid_i++];
 
-        cpu_x86_cpuid(env, i, 0, &eax, &ebx, &ecx, &edx);
         c->function = i;
-        c->eax = eax;
-        c->ebx = ebx;
-        c->ecx = ecx;
-        c->edx = edx;
+        c->flags = 0;
+        cpu_x86_cpuid(env, i, 0, &c->eax, &c->ebx, &c->ecx, &c->edx);
     }
 
     cpuid_data.cpuid.nent = cpuid_i;

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