linux-kernel - Re: [PATCH 3/5] x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path

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Message-ID: <20201020094110.GG9328@suse.de>
Date:   Tue, 20 Oct 2020 11:41:10 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Arvind Sankar <nivedita@...m.mit.edu>
Cc:     Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Martin Radev <martin.b.radev@...il.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] x86/boot/compressed/64: Check SEV encryption in
 64-bit boot-path

On Mon, Oct 19, 2020 at 05:22:47PM -0400, Arvind Sankar wrote:
> The boot cpu also enables CR4.PGE -- that code is shared between boot
> and secondary cpus. The boot cpu jumps to the first "1" label below,
> just before the call to sev_verify_cbit you're adding.

You are right, in the real kernel image PGE gets enabled early. I added
code to save and restore CR4 in sev_verify_cbit() and disable PGE during
the test.

Thanks,

	Joerg