linux-kernel - Re: [PATCH v6 31/76] x86/head/64: Setup MSR_GS

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Message-ID: <20200901120956.GA22385@8bytes.org>
Date:   Tue, 1 Sep 2020 14:09:56 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, Joerg Roedel <jroedel@...e.de>,
        Kees Cook <keescook@...omium.org>, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v6 31/76] x86/head/64: Setup MSR_GS_BASE before calling
 into C code

On Fri, Aug 28, 2020 at 08:13:46PM +0200, Borislav Petkov wrote:
> On Mon, Aug 24, 2020 at 10:54:26AM +0200, Joerg Roedel wrote:
> > +	movl	$MSR_GS_BASE,%ecx
> 
> I'm confused: is this missing those three lines:
> 
>         movl    initial_gs(%rip),%eax
>         movl    initial_gs+4(%rip),%edx
>         wrmsr
> 
> as it is done in secondary_startup_64 ?

No, it is a leftover from before I moved the MSR write into
startup_64_setup_env(). I removed it, thanks for catching this.

Regards,

	Joerg