[Qemu-devel] [PATCH 2/2] target-i386: do not special case TSC writeback

["Fernando Luis Vázquez Cao" <fernando_b1@lab.ntt.co.jp>]

Newer kernels are capable of synchronizing TSC values of multiple VCPUs
on writeback, but we were excluding the power up case, which is not needed
anymore.

Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
---

diff -urNp qemu-orig/target-i386/kvm.c qemu/target-i386/kvm.c
--- qemu-orig/target-i386/kvm.c	2013-12-06 16:12:03.201953736 +0900
+++ qemu/target-i386/kvm.c	2013-12-06 16:13:53.897955184 +0900
@@ -1144,15 +1144,7 @@ static int kvm_put_msrs(X86CPU *cpu, int
      * for normal writeback. Limit them to reset or full state updates.
      */
     if (level >= KVM_PUT_RESET_STATE) {
-        /*
-         * KVM is yet unable to synchronize TSC values of multiple VCPUs on
-         * writeback. Until this is fixed, we only write the offset to SMP
-         * guests after migration, desynchronizing the VCPUs, but avoiding
-         * huge jump-backs that would occur without any writeback at all.
-         */
-        if (smp_cpus == 1 || env->tsc != 0 || level == KVM_PUT_RESET_STATE) {
-            kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSC, env->tsc);
-        }
+        kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSC, env->tsc);
         kvm_msr_entry_set(&msrs[n++], MSR_KVM_SYSTEM_TIME,
                           env->system_time_msr);
         kvm_msr_entry_set(&msrs[n++], MSR_KVM_WALL_CLOCK, env->wall_clock_msr);