[PATCH v2 00/12] KVM: x86: add support for VMX TSC scaling

[Haozhong Zhang]

This patchset adds support for VMX TSC scaling feature which is
available on Intel Skylake CPU. The specification of VMX TSC scaling
can be found at
http://www.intel.com/content/www/us/en/processors/timestamp-counter-scaling-virtualization-white-paper.html

VMX TSC scaling allows guest TSC which is read by guest rdtsc(p)
instructions increases in a rate that is customized by the hypervisor
and can be different than the host TSC rate. Basically, VMX TSC
scaling adds a 64-bit field called TSC multiplier in VMCS so that, if
VMX TSC scaling is enabled, TSC read by guest rdtsc(p) instructions
will be calculated by the following formula:

  guest EDX:EAX = (Host TSC * TSC multiplier) >> 48 + VMX TSC Offset

where, Host TSC = Host MSR_IA32_TSC + Host MSR_IA32_TSC_ADJUST.

This patchset, when cooperating with another QEMU patchset (sent in
another email "target-i386: save/restore vcpu's TSC rate during
migration"), allows guest programs observe a consistent TSC rate even
though they are migrated among machines with different host TSC rates.

VMX TSC scaling shares some common logics with SVM TSC ratio which
is already supported by KVM. Patch 1 ~ 8 move those common logics from
SVM code to the common code. Upon them, patch 9 ~ 12 add VMX-specific
support for VMX TSC scaling.

Changes in v2:
 * Remove the duplicated variable 'kvm_tsc_scaling_ratio_rsvd'.
 * Remove an unnecessary error check in original patch 2.
 * Do 64-bit arithmetic by functions recommended by Paolo.
 * Make kvm_set_tsc_khz() returns an error number so that ioctl
   KVM_SET_TSC_KHZ does not return 0 if errors happen.

Reviewed-by: Eric Northup <digitaleric@xxxxxxxxxx>

Haozhong Zhang (12):
  KVM: x86: Collect information for setting TSC scaling ratio
  KVM: x86: Add a common TSC scaling ratio field in kvm_vcpu_arch
  KVM: x86: Add a common TSC scaling function
  KVM: x86: Replace call-back set_tsc_khz() with a common function
  KVM: x86: Replace call-back compute_tsc_offset() with a common function
  KVM: x86: Move TSC scaling logic out of call-back adjust_tsc_offset()
  KVM: x86: Move TSC scaling logic out of call-back read_l1_tsc()
  KVM: x86: Use the correct vcpu's TSC rate to compute time scale
  KVM: VMX: Enable and initialize VMX TSC scaling
  KVM: VMX: Setup TSC scaling ratio when a vcpu is loaded
  KVM: VMX: Use a scaled host TSC for guest readings of MSR_IA32_TSC
  KVM: VMX: Dump TSC multiplier in dump_vmcs()

 arch/x86/include/asm/kvm_host.h |  24 +++----
 arch/x86/include/asm/vmx.h      |   3 +
 arch/x86/kvm/lapic.c            |   4 +-
 arch/x86/kvm/svm.c              | 116 ++++------------------------------
 arch/x86/kvm/vmx.c              |  64 ++++++++++---------
 arch/x86/kvm/x86.c              | 134 +++++++++++++++++++++++++++++++++++-----
 include/linux/kvm_host.h        |  20 ++++++
 include/linux/math64.h          |  99 +++++++++++++++++++++++++++++
 8 files changed, 297 insertions(+), 167 deletions(-)

-- 
2.4.8

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