kvmclock: use the updated system_timer_msr

Fixes e2b6c171 (kvmclock: update system_time_msr address forcibly)
which makes a call to get the latest value of the address
stored in system_timer_msr, but then uses the old address anyway.
Signed-off-by: NJim Somerville <Jim.Somerville@windriver.com>
Message-Id: <59b67db0bd15a46ab47c3aa657c81a4c11f168ea.1506702472.git.Jim.Somerville@windriver.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

hw/i386/kvm/clock.c

@@ -62,7 +62,7 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s)
 {
     CPUState *cpu = first_cpu;
     CPUX86State *env = cpu->env_ptr;
-    hwaddr kvmclock_struct_pa = env->system_time_msr & ~1ULL;
+    hwaddr kvmclock_struct_pa;
     uint64_t migration_tsc = env->tsc;
     struct pvclock_vcpu_time_info time;
     uint64_t delta;
@@ -77,6 +77,7 @@ static uint64_t kvmclock_current_nsec(KVMClockState *s)
         return 0;
     }
 
+    kvmclock_struct_pa = env->system_time_msr & ~1ULL;
     cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time));
 
     assert(time.tsc_timestamp <= migration_tsc);