Re: [PATCH v8 0/3] KVM: x86: Enable user wait instructions

[Tao Xu]

On 7/20/2019 1:18 AM, Paolo Bonzini wrote:
> On 19/07/19 08:31, Tao Xu wrote:
> > Ping for comments :)
>
> Hi, I'll look at it for 5.4, right after the merge window.
>
> Paolo
Thank you Paolo!

> > On 7/16/2019 2:55 PM, Tao Xu wrote:
> > > UMONITOR, UMWAIT and TPAUSE are a set of user wait instructions.
> > >
> > > UMONITOR arms address monitoring hardware using an address. A store
> > > to an address within the specified address range triggers the
> > > monitoring hardware to wake up the processor waiting in umwait.
> > >
> > > UMWAIT instructs the processor to enter an implementation-dependent
> > > optimized state while monitoring a range of addresses. The optimized
> > > state may be either a light-weight power/performance optimized state
> > > (c0.1 state) or an improved power/performance optimized state
> > > (c0.2 state).
> > >
> > > TPAUSE instructs the processor to enter an implementation-dependent
> > > optimized state c0.1 or c0.2 state and wake up when time-stamp counter
> > > reaches specified timeout.
> > >
> > > Availability of the user wait instructions is indicated by the presence
> > > of the CPUID feature flag WAITPKG CPUID.0x07.0x0:ECX[5].
> > >
> > > The patches enable the umonitor, umwait and tpause features in KVM.
> > > Because umwait and tpause can put a (psysical) CPU into a power saving
> > > state, by default we dont't expose it to kvm and enable it only when
> > > guest CPUID has it. If the instruction causes a delay, the amount
> > > of time delayed is called here the physical delay. The physical delay is
> > > first computed by determining the virtual delay (the time to delay
> > > relative to the VMâs timestamp counter).
> > >
> > > The release document ref below link:
> > > Intel 64 and IA-32 Architectures Software Developer's Manual,
> > > https://software.intel.com/sites/default/files/\
> > > managed/39/c5/325462-sdm-vol-1-2abcd-3abcd.pdf
> > >
> > > Changelog:
> > > v8:
> > >  ÂÂÂÂAdd vmx_waitpkg_supported() helper (Sean)
> > >  ÂÂÂÂAdd an accessor to expose umwait_control_cached (Sean)
> > >  ÂÂÂÂSet msr_ia32_umwait_control in vcpu_vmx u32 and raise #GP when
> > >  ÂÂÂÂ[63:32] is set when rdmsr. (Sean)
> > >  ÂÂÂÂIntroduce a common exit helper handle_unexpected_vmexit (Sean)
> > > v7:
> > >  ÂÂÂÂAdd nested support for user wait instructions (Paolo)
> > >  ÂÂÂÂUse the test on vmx->secondary_exec_control to replace
> > >  ÂÂÂÂguest_cpuid_has (Paolo)
> > > v6:
> > >  ÂÂÂÂadd check msr_info->host_initiated in get/set msr(Xiaoyao)
> > >  ÂÂÂÂrestore the atomic_switch_umwait_control_msr()(Xiaoyao)
> > >
> > > Tao Xu (3):
> > >  ÂÂ KVM: x86: Add support for user wait instructions
> > >  ÂÂ KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL
> > >  ÂÂ KVM: vmx: Introduce handle_unexpected_vmexit and handle WAITPKG vmexit
> > >
> > >  Â arch/x86/include/asm/vmx.hÂÂÂÂÂ |Â 1 +
> > >  Â arch/x86/include/uapi/asm/vmx.h |Â 6 ++-
> > >  Â arch/x86/kernel/cpu/umwait.cÂÂÂ |Â 6 +++
> > >  Â arch/x86/kvm/cpuid.cÂÂÂÂÂÂÂÂÂÂÂ |Â 2 +-
> > >  Â arch/x86/kvm/vmx/capabilities.h |Â 6 +++
> > >  Â arch/x86/kvm/vmx/nested.cÂÂÂÂÂÂ |Â 5 ++
> > >  Â arch/x86/kvm/vmx/vmx.cÂÂÂÂÂÂÂÂÂ | 83 ++++++++++++++++++++++++++-------
> > >  Â arch/x86/kvm/vmx/vmx.hÂÂÂÂÂÂÂÂÂ |Â 9 ++++
> > >  Â arch/x86/kvm/x86.cÂÂÂÂÂÂÂÂÂÂÂÂÂ |Â 1 +
> > >  Â 9 files changed, 101 insertions(+), 18 deletions(-)