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

[Haozhong Zhang <haozhong.zhang@intel.com>]

On Mon, Sep 28, 2015 at 09:00:39PM -0700, Eric Northup wrote:
> On Sun, Sep 27, 2015 at 10:37 PM, Haozhong Zhang
> <haozhong.zhang@intel.com> wrote:
> > 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 scaling 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.
> 
> reviewed-by: Eric Northup <digitaleric@google.com>
>

Thank you for the review!

> >
> > 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      |   4 +-
> >  arch/x86/kvm/lapic.c            |   5 +-
> >  arch/x86/kvm/svm.c              | 113 +++--------------------------
> >  arch/x86/kvm/vmx.c              |  60 ++++++++--------
> >  arch/x86/kvm/x86.c              | 154 +++++++++++++++++++++++++++++++++++++---
> >  include/linux/kvm_host.h        |  21 +++++-
> >  7 files changed, 221 insertions(+), 160 deletions(-)
> >
> > --
> > 2.4.8
> >
> > --
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