linux-kernel - Re: [PATCH v2 05/16] KVM: VMX: Drop initialization of IA32_FEATURE

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Message-ID: <20191025162645.GE6483@zn.tnic>
Date:   Fri, 25 Oct 2019 18:26:45 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>, kvm@...r.kernel.org
Subject: Re: [PATCH v2 05/16] KVM: VMX: Drop initialization of
 IA32_FEATURE_CONTROL MSR

On Mon, Oct 21, 2019 at 05:08:20PM -0700, Sean Christopherson wrote:
> +	if (WARN_ON_ONCE(!(msr & FEATURE_CONTROL_LOCKED)))
> +		return 1;
> +
> +	/* launched w/ TXT and VMX disabled */
> +	if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX) &&
> +	    tboot_enabled())
> +		return 1;
> +	/* launched w/o TXT and VMX only enabled w/ TXT */
> +	if (!(msr & FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX) &&
> +	    (msr & FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX) &&
> +	    !tboot_enabled()) {
> +		pr_warn("kvm: disable TXT in the BIOS or "
> +			"activate TXT before enabling KVM\n");
> +		return 1;

Might as well fix that with a cleanup patch ontop:

WARNING: quoted string split across lines
#69: FILE: arch/x86/kvm/vmx/vmx.c:2208:
+               pr_warn("kvm: disable TXT in the BIOS or "
+                       "activate TXT before enabling KVM\n");


Also in that same cleanup patch, if the order of those tests doesn't
matter, you can simplify them a bit:

	if (tboot_enabled()) {
		/* msr flag test here */

	/* tboot disabled */
	} else {
		/* other two tests here */
	}

Should make it a bit easier to parse.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette