linux-kernel - Re: [PATCH v2 3/3] KVM: vmx: handle vm-exit for UMWAIT and TPAUSE

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Message-ID: <a2b463ee-c032-555e-b012-184e4f4753f1@intel.com>
Date:   Wed, 29 May 2019 10:25:14 +0800
From:   Tao Xu <tao3.xu@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     rkrcmar@...hat.com, corbet@....net, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        sean.j.christopherson@...el.com, x86@...nel.org,
        kvm@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, jingqi.liu@...el.com
Subject: Re: [PATCH v2 3/3] KVM: vmx: handle vm-exit for UMWAIT and TPAUSE

On 29/05/2019 09:28, Paolo Bonzini wrote:
> On 24/05/19 09:56, Tao Xu wrote:
>> As the latest Intel 64 and IA-32 Architectures Software Developer's
>> Manual, UMWAIT and TPAUSE instructions cause a VM exit if the
>> “RDTSC exiting” and “enable user wait and pause” VM-execution controls
>> are both 1.
>>
>> This patch is to handle the vm-exit for UMWAIT and TPAUSE as invalid_op.
> 
> KVM never enables RDTSC exiting, so this is not necessary.
> 
> Paolo
> 
OK, but should we just drop this patch?
Or add the VMX_EXIT_REASONS bits of UMWAIT and TPAUSE and handle like 
XSAVES/XRSTORS:
"kvm_skip_emulated_instruction(vcpu);"
"WARN(1, "this should never happen\n");"

Looking forward to your reply.

Tao