This patchset enables QEMU to save/restore vcpu's TSC rate during the
migration on machine types pc-*-2.5 or newer.

On the source machine:
 * If the vcpu's TSC rate is specified by the cpu option 'tsc-freq',
   then this user-specified TSC rate will be migrated.
 * Otherwise, the TSC rate returned by KVM_GET_TSC_KHZ will be
   migrated. For a fresh VM, this is the host TSC rate.

On the destination machine:
 * If the vcpu's TSC rate is specified by the cpu option 'tsc-freq',
   then QEMU will try to use this user-specified TSC rate rather than
   the migrated value.
 * Otherwise, QEMU will try to use the migrated TSC rate. If KVM on
   the destination supports TSC scaling, guest programs will observe a
   consistent TSC rate across the migration. If TSC scaling is not
   supported, the migration will not be aborted and QEMU will behave
   like before, i.e using the host TSC rate instead.

Changes in v3:
 * Change the cpu option 'save-tsc-freq' to an internal flag.
 * Remove the cpu option 'load-tsc-freq' and change the logic of
   loading the migrated TSC rate as above.
 * Move the setup of migrated TSC rate back to

Changes in v2:
 * Add a pair of cpu options 'save-tsc-freq' and 'load-tsc-freq' to
   control the migration of vcpu's TSC rate.
 * Move all logic of setting TSC rate to target-i386.
 * Remove the duplicated TSC setup in kvm_arch_init_vcpu().

Haozhong Zhang (3):
  target-i386: add a subsection for migrating vcpu's TSC rate
  target-i386: calculate vcpu's TSC rate to be migrated
  target-i386: load the migrated vcpu's TSC rate

 hw/i386/pc.c          |  1 +
 hw/i386/pc_piix.c     |  1 +
 hw/i386/pc_q35.c      |  1 +
 include/hw/i386/pc.h  |  1 +
 include/sysemu/kvm.h  |  2 ++
 kvm-all.c             |  1 +
 target-arm/kvm.c      |  5 +++++
 target-i386/cpu.h     |  1 +
 target-i386/kvm.c     | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++
 target-i386/machine.c | 21 ++++++++++++++++++++
 target-mips/kvm.c     |  5 +++++
 target-ppc/kvm.c      |  5 +++++
 target-s390x/kvm.c    |  5 +++++
 13 files changed, 103 insertions(+)


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