linux-kernel - Re: [PATCH v9 09/12] KVM: x86: Introduce a function to initialize the PT configuration

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Message-ID: <c3a25e58-cb4e-f3f7-bbd5-559bc763bb26@redhat.com>
Date:   Mon, 11 Jun 2018 13:41:53 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     "Kang, Luwei" <luwei.kang@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "thomas.lendacky@....com" <thomas.lendacky@....com>,
        "bp@...e.de" <bp@...e.de>, "Liang, Kan" <kan.liang@...el.com>,
        "Janakarajan.Natarajan@....com" <Janakarajan.Natarajan@....com>,
        "dwmw@...zon.co.uk" <dwmw@...zon.co.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "mathieu.poirier@...aro.org" <mathieu.poirier@...aro.org>,
        "kstewart@...uxfoundation.org" <kstewart@...uxfoundation.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "david@...hat.com" <david@...hat.com>,
        "bsd@...hat.com" <bsd@...hat.com>,
        "yu.c.zhang@...ux.intel.com" <yu.c.zhang@...ux.intel.com>,
        "joro@...tes.org" <joro@...tes.org>
Subject: Re: [PATCH v9 09/12] KVM: x86: Introduce a function to initialize the
 PT configuration

On 08/06/2018 16:56, Kang, Luwei wrote:
>>> +	/* Initialize and clear the no dependency bits */
>>> +	vmx->pt_desc.ctl_bitmask = ~0ULL;
>> This looks redundant, doesn't it?
> This is a bit mask for RTIT_CTL MSR and it will make & with the value of RTIT_CLT from guest.
> The reserved bits will be 1 in this bit mask and the setable  bits are 0.
> 
>>> +	vmx->pt_desc.ctl_bitmask = ~(RTIT_CTL_TRACEEN | RTIT_CTL_OS |
>>> +			RTIT_CTL_USR | RTIT_CTL_TSC_EN |
>> RTIT_CTL_DISRETC);

But it's set twice, so the first assignment is superfluous.

Paolo