linux-kernel - Re: [PATCH 08/62] x86/boot/compressed/64: Add IDT Infrastructure

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Date:   Fri, 14 Feb 2020 11:40:36 -0800
From:   Andi Kleen <ak@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Hellstrom <thellstrom@...are.com>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 08/62] x86/boot/compressed/64: Add IDT Infrastructure

Joerg Roedel <joro@...tes.org> writes:
> +	addq    $8, %rsp
> +
> +	/*
> +	 * Make sure we return to __KERNEL_CS - the CS selector on
> +	 * the IRET frame might still be from an old BIOS GDT
> +	 */
> +	movq	$__KERNEL_CS, 8(%rsp)

This doesn't make sense. Either it's running on the correct CS
before the exception or not. Likely there's some other problem
here that you patched over with this hack.

-Andi