[Qemu-devel] [PATCH v2] kvm: Allow the Hyper-V vendor ID to be specified

[Alex Williamson <alex.williamson@redhat.com>]

According to Microsoft documentation, the signature in the standard
hypervisor CPUID leaf at 0x40000000 identifies the Vendor ID and is
for reporting and diagnostic purposes only.  We can therefore allow
the user to change it to whatever they want, within the 12 character
limit.  Add a new hyperv-vendor-id option to the -cpu flag to allow
for this, ex:

 -cpu host,hv_time,hv_vendor_id=KeenlyKVM

Link: http://msdn.microsoft.com/library/windows/hardware/hh975392
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

v2: Replace abort() with truncating the string, error report updated

Igor also had the idea of creating a DEFINE_PROP_STRING_LEN property
where we could enforce the length earlier in the parameter checking.
If we like that idea, we probably need to do it first since we don't
want to switch from truncating to erroring between releases.  I can
work on that if preferred.  Thanks,

Alex

 target-i386/cpu-qom.h |    1 +
 target-i386/cpu.c     |    1 +
 target-i386/kvm.c     |   14 +++++++++++++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/target-i386/cpu-qom.h b/target-i386/cpu-qom.h
index c35b624..6c1eaaa 100644
--- a/target-i386/cpu-qom.h
+++ b/target-i386/cpu-qom.h
@@ -88,6 +88,7 @@ typedef struct X86CPU {
     bool hyperv_vapic;
     bool hyperv_relaxed_timing;
     int hyperv_spinlock_attempts;
+    char *hyperv_vendor_id;
     bool hyperv_time;
     bool hyperv_crash;
     bool check_cpuid;
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 05d7f26..71df546 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -3146,6 +3146,7 @@ static Property x86_cpu_properties[] = {
     DEFINE_PROP_UINT32("level", X86CPU, env.cpuid_level, 0),
     DEFINE_PROP_UINT32("xlevel", X86CPU, env.cpuid_xlevel, 0),
     DEFINE_PROP_UINT32("xlevel2", X86CPU, env.cpuid_xlevel2, 0),
+    DEFINE_PROP_STRING("hv-vendor-id", X86CPU, hyperv_vendor_id),
     DEFINE_PROP_END_OF_LIST()
 };
 
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 80d1a7e..9d25fd7 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -490,7 +490,19 @@ int kvm_arch_init_vcpu(CPUState *cs)
     if (hyperv_enabled(cpu)) {
         c = &cpuid_data.entries[cpuid_i++];
         c->function = HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS;
-        memcpy(signature, "Microsoft Hv", 12);
+        if (!cpu->hyperv_vendor_id) {
+            memcpy(signature, "Microsoft Hv", 12);
+        } else {
+            size_t len = strlen(cpu->hyperv_vendor_id);
+
+            if (len > 12) {
+                fprintf(stderr,
+                        "hyperv-vendor-id too long, truncated to 12 charaters");
+                len = 12;
+            }
+            memset(signature, 0, 12);
+            memcpy(signature, cpu->hyperv_vendor_id, len);
+        }
         c->eax = HYPERV_CPUID_MIN;
         c->ebx = signature[0];
         c->ecx = signature[1];