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

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Message-ID: <a4bbc34c-9a0a-1bfb-2d56-c71a8d9a52c9@redhat.com>
Date:   Tue, 17 Sep 2019 19:05:17 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Tao Xu <tao3.xu@...el.com>, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, corbet@....net,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        jingqi.liu@...el.com
Subject: Re: [PATCH v8 0/3] KVM: x86: Enable user wait instructions

On 16/09/19 03:28, Tao Xu wrote:
> 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
>>
> Hi paolo,
> 
> Linux 5.3 has released, could you review these patches. Thank you very
> much!
> 
> Tao
>>> 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 VM’s 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:
>>>>      Add vmx_waitpkg_supported() helper (Sean)
>>>>      Add an accessor to expose umwait_control_cached (Sean)
>>>>      Set msr_ia32_umwait_control in vcpu_vmx u32 and raise #GP when
>>>>      [63:32] is set when rdmsr. (Sean)
>>>>      Introduce a common exit helper handle_unexpected_vmexit (Sean)
>>>> v7:
>>>>      Add nested support for user wait instructions (Paolo)
>>>>      Use the test on vmx->secondary_exec_control to replace
>>>>      guest_cpuid_has (Paolo)
>>>> v6:
>>>>      add check msr_info->host_initiated in get/set msr(Xiaoyao)
>>>>      restore the atomic_switch_umwait_control_msr()(Xiaoyao)
>>>>
>>>> Tao Xu (3):
>>>>     KVM: x86: Add support for user wait instructions
>>>>     KVM: vmx: Emulate MSR IA32_UMWAIT_CONTROL
>>>>     KVM: vmx: Introduce handle_unexpected_vmexit and handle WAITPKG
>>>> vmexit
>>>>
>>>>    arch/x86/include/asm/vmx.h      |  1 +
>>>>    arch/x86/include/uapi/asm/vmx.h |  6 ++-
>>>>    arch/x86/kernel/cpu/umwait.c    |  6 +++
>>>>    arch/x86/kvm/cpuid.c            |  2 +-
>>>>    arch/x86/kvm/vmx/capabilities.h |  6 +++
>>>>    arch/x86/kvm/vmx/nested.c       |  5 ++
>>>>    arch/x86/kvm/vmx/vmx.c          | 83
>>>> ++++++++++++++++++++++++++-------
>>>>    arch/x86/kvm/vmx/vmx.h          |  9 ++++
>>>>    arch/x86/kvm/x86.c              |  1 +
>>>>    9 files changed, 101 insertions(+), 18 deletions(-)
>>>>
>>>
>>
> 

Queued, thanks.

Paolo