target-i386: Enabling IA32_TSC_ADJUST for QEMU KVM guest VMs

CPUID.7.0.EBX[1]=1 indicates IA32_TSC_ADJUST MSR 0x3b is supported

Basic design is to emulate the MSR by allowing reads and writes to the
hypervisor vcpu specific locations to store the value of the emulated MSRs.
In this way the IA32_TSC_ADJUST value will be included in all reads to
the TSC MSR whether through rdmsr or rdtsc.

As this is a new MSR that the guest may access and modify its value needs
to be migrated along with the other MRSs. The changes here are specifically
for recognizing when IA32_TSC_ADJUST is enabled in CPUID and code added
for migrating its value.

Signed-off-by: Will Auld <will.auld@intel.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index f669281..ae6ce1f 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -62,6 +62,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
 
 static bool has_msr_star;
 static bool has_msr_hsave_pa;
+static bool has_msr_tsc_adjust;
 static bool has_msr_tsc_deadline;
 static bool has_msr_async_pf_en;
 static bool has_msr_pv_eoi_en;
@@ -676,6 +677,10 @@ static int kvm_get_supported_msrs(KVMState *s)
                     has_msr_hsave_pa = true;
                     continue;
                 }
+                if (kvm_msr_list->indices[i] == MSR_TSC_ADJUST) {
+                    has_msr_tsc_adjust = true;
+                    continue;
+                }
                 if (kvm_msr_list->indices[i] == MSR_IA32_TSCDEADLINE) {
                     has_msr_tsc_deadline = true;
                     continue;
@@ -1013,6 +1018,9 @@ static int kvm_put_msrs(CPUX86State *env, int level)
     if (has_msr_hsave_pa) {
         kvm_msr_entry_set(&msrs[n++], MSR_VM_HSAVE_PA, env->vm_hsave);
     }
+    if (has_msr_tsc_adjust) {
+        kvm_msr_entry_set(&msrs[n++], MSR_TSC_ADJUST, env->tsc_adjust);
+    }
     if (has_msr_tsc_deadline) {
         kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSCDEADLINE, env->tsc_deadline);
     }
@@ -1273,6 +1281,9 @@ static int kvm_get_msrs(CPUX86State *env)
     if (has_msr_hsave_pa) {
         msrs[n++].index = MSR_VM_HSAVE_PA;
     }
+    if (has_msr_tsc_adjust) {
+        msrs[n++].index = MSR_TSC_ADJUST;
+    }
     if (has_msr_tsc_deadline) {
         msrs[n++].index = MSR_IA32_TSCDEADLINE;
     }
@@ -1350,6 +1361,9 @@ static int kvm_get_msrs(CPUX86State *env)
         case MSR_IA32_TSC:
             env->tsc = msrs[i].data;
             break;
+        case MSR_TSC_ADJUST:
+            env->tsc_adjust = msrs[i].data;
+            break;
         case MSR_IA32_TSCDEADLINE:
             env->tsc_deadline = msrs[i].data;
             break;