linux-kernel - RE: [PATCH v1 05/23] KVM: VMX: Initialize FRED VM entry/exit controls in vmcs

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Message-ID: <SA1PR11MB67345334BC2384D0785C8416A8B1A@SA1PR11MB6734.namprd11.prod.outlook.com>
Date:   Wed, 15 Nov 2023 02:39:53 +0000
From:   "Li, Xin3" <xin3.li@...el.com>
To:     Nikolay Borisov <nik.borisov@...e.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
CC:     "seanjc@...gle.com" <seanjc@...gle.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "Cui, Dexuan" <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>
Subject: RE: [PATCH v1 05/23] KVM: VMX: Initialize FRED VM entry/exit controls
 in vmcs_config

> > -	if (_vmexit_control & VM_EXIT_ACTIVATE_SECONDARY_CONTROLS)
> > +	if (_vmexit_control & VM_EXIT_ACTIVATE_SECONDARY_CONTROLS) {
> >   		_secondary_vmexit_control =
> >
> 	adjust_vmx_controls64(KVM_OPTIONAL_VMX_SECONDARY_VM_EXIT_CO
> NTROLS,
> >   					      MSR_IA32_VMX_EXIT_CTLS2);
> > +		if (cpu_feature_enabled(X86_FEATURE_FRED) &&
> > +		    !(_secondary_vmexit_control &
> SECONDARY_VM_EXIT_SAVE_IA32_FRED &&
> > +		      _secondary_vmexit_control &
> SECONDARY_VM_EXIT_LOAD_IA32_FRED)) {
> 
> Can those checks actually trigger? I.e if FEATURE_FRED is set it means
> the CPU implements the FRED spec. According to the spec it's guaranteed
> that VMX_EXIT_CTLS2 will contain those bits set to 1. So aren't those
> checks superfluous?

Such checks are for nVMX FRED.

> > +	if (cpu_feature_enabled(X86_FEATURE_FRED) &&
> > +	    !(_vmentry_control & VM_ENTRY_LOAD_IA32_FRED)) {
> DITTO
> 
> <snip>