[Qemu-devel] [PATCH 2/2] introduce -cpu host target

[Andre Przywara]

Although the guest's CPUID bits can be controlled in a fine grained way
in QEMU, a simple way to inject the host CPU is missing. This is handy
for KVM desktop virtualization, where one wants the guest to support the
full host feature set.
Introduce another CPU type called 'host', which will propagate the host's
CPUID bits to the guest. Problematic bits can still be turned off by using
the existing syntax (-cpu host,-skinit)

Signed-off-by: Andre Przywara <address@hidden>
---
 target-i386/helper.c |   65 +++++++++++++++++++++++++++++++++++++++++++++----
 1 files changed, 59 insertions(+), 6 deletions(-)

I know that this has some more implications, currently it does not boot
Linux kernels on AMD K8 and Fam10h boxes with KVM. I will send out patches
for KVM to fix these issues (unhandled MSRs) later.
Should we ignore unhandled MSRs like QEMU or Xen do?
Also I want to hear your opinions on disabling CPUID bits afterwards
(like ibs, skinit and other things we don't virtualize yet).

Thanks and Regards,
Andre.

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 529f962..80b5621 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -273,9 +273,9 @@ static x86_def_t x86_defs[] = {
     {
         .name = "athlon",
         .level = 2,
-        .vendor1 = 0x68747541, /* "Auth" */
-        .vendor2 = 0x69746e65, /* "enti" */
-        .vendor3 = 0x444d4163, /* "cAMD" */
+        .vendor1 = CPUID_VENDOR_AMD_1,
+        .vendor2 = CPUID_VENDOR_AMD_2,
+        .vendor3 = CPUID_VENDOR_AMD_3,
         .family = 6,
         .model = 2,
         .stepping = 3,
@@ -308,6 +308,54 @@ static x86_def_t x86_defs[] = {
     },
 };
 
+static void host_cpuid(uint32_t function, uint32_t count, uint32_t *eax,
+                               uint32_t *ebx, uint32_t *ecx, uint32_t *edx);
+
+static int cpu_x86_fill_model_id(char *str)
+{
+    uint32_t eax, ebx, ecx, edx;
+    int i;
+
+    for (i = 0; i < 3; i++) {
+        host_cpuid(0x80000002 + i, 0, &eax, &ebx, &ecx, &edx);
+        memcpy(str + i * 16 +  0, &eax, 4);
+        memcpy(str + i * 16 +  4, &ebx, 4);
+        memcpy(str + i * 16 +  8, &ecx, 4);
+        memcpy(str + i * 16 + 12, &edx, 4);
+    }
+    return 0;
+}
+
+static int cpu_x86_fill_host(x86_def_t *x86_cpu_def)
+{
+    uint32_t eax, ebx, ecx, edx;
+
+    x86_cpu_def->name = "host";
+    host_cpuid(0x0, 0, &eax, &ebx, &ecx, &edx);
+    x86_cpu_def->level = eax;
+    x86_cpu_def->vendor1 = ebx;
+    x86_cpu_def->vendor2 = edx;
+    x86_cpu_def->vendor3 = ecx;
+
+    host_cpuid(0x1, 0, &eax, &ebx, &ecx, &edx);
+    x86_cpu_def->family = ((eax >> 8) & 0x0F) + ((eax >> 20) & 0xFF);
+    x86_cpu_def->model = ((eax >> 4) & 0x0F) | ((eax & 0xF0000) >> 12);
+    x86_cpu_def->stepping = eax & 0x0F;
+    x86_cpu_def->ext_features = ecx;
+    x86_cpu_def->features = edx;
+
+    host_cpuid(0x80000000, 0, &eax, &ebx, &ecx, &edx);
+    x86_cpu_def->xlevel = eax;
+
+    host_cpuid(0x80000001, 0, &eax, &ebx, &ecx, &edx);
+    x86_cpu_def->ext2_features = edx;
+    x86_cpu_def->ext3_features = ecx;
+    cpu_x86_fill_model_id(x86_cpu_def->model_id);
+    x86_cpu_def->vendor_override = 0;
+
+    return 0;
+}
+
 static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, const char *cpu_model)
 {
     unsigned int i;
@@ -326,9 +374,14 @@ static int cpu_x86_find_by_name(x86_def_t *x86_cpu_def, 
const char *cpu_model)
             break;
         }
     }
-    if (!def)
-        goto error;
-    memcpy(x86_cpu_def, def, sizeof(*def));
+    if (!def) {
+        if (strcmp(name, "host") != 0) {
+            goto error;
+        }
+        cpu_x86_fill_host(x86_cpu_def);
+    } else {
+        memcpy(x86_cpu_def, def, sizeof(*def));
+    }
 
     if (kvm_enabled()) {
         add_flagname_to_bitmaps("hypervisor", &plus_features,
-- 
1.6.1.3