linux-kernel - Re: [PATCH v5 33/75] x86/head/64: Switch to initial stack earlier

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Message-ID: <202007241043.96A920ADEC@keescook>
Date:   Fri, 24 Jul 2020 10:43:07 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, Joerg Roedel <jroedel@...e.de>, 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 v5 33/75] x86/head/64: Switch to initial stack earlier

On Fri, Jul 24, 2020 at 06:02:54PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> Make sure there is a stack once the kernel runs from virual addresses.
> At this stage any secondary CPU which boots will have lost its stack
> because the kernel switched to a new page-table which does not map the
> real-mode stack anymore.
> 
> This is needed for handling early #VC exceptions caused by instructions
> like CPUID.
> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook