From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=tP1Z=4A=vger.kernel.org=kvm-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no
	autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 6CDFDC2BA83
	for <kvm@archiver.kernel.org>; Wed, 12 Feb 2020 11:19:57 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id 4FB0A21739
	for <kvm@archiver.kernel.org>; Wed, 12 Feb 2020 11:19:57 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1727960AbgBLLTv (ORCPT <rfc822;kvm@archiver.kernel.org>);
        Wed, 12 Feb 2020 06:19:51 -0500
Received: from 8bytes.org ([81.169.241.247]:53636 "EHLO theia.8bytes.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1727947AbgBLLTv (ORCPT <rfc822;kvm@vger.kernel.org>);
        Wed, 12 Feb 2020 06:19:51 -0500
Received: by theia.8bytes.org (Postfix, from userid 1000)
        id 50C2B4A6; Wed, 12 Feb 2020 12:19:49 +0100 (CET)
Date:   Wed, 12 Feb 2020 12:19:24 +0100
From:   Joerg Roedel <joro@8bytes.org>
To:     Andy Lutomirski <luto@kernel.org>
Cc:     X86 ML <x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Hellstrom <thellstrom@vmware.com>,
        Jiri Slaby <jslaby@suse.cz>,
        Dan Williams <dan.j.williams@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Juergen Gross <jgross@suse.com>,
        Kees Cook <keescook@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>,
        kvm list <kvm@vger.kernel.org>,
        Linux Virtualization <virtualization@lists.linux-foundation.org>,
        Joerg Roedel <jroedel@suse.de>
Subject: Re: [PATCH 08/62] x86/boot/compressed/64: Add IDT Infrastructure
Message-ID: <20200212111923.GA20066@8bytes.org>
References: <20200211135256.24617-1-joro@8bytes.org>
 <20200211135256.24617-9-joro@8bytes.org>
 <CALCETrWznWHQNfd80G95G_CB-yCw8Botqee8bsLz3OcC4-SS=w@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CALCETrWznWHQNfd80G95G_CB-yCw8Botqee8bsLz3OcC4-SS=w@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: kvm-owner@vger.kernel.org
Precedence: bulk
List-ID: <kvm.vger.kernel.org>
X-Mailing-List: kvm@vger.kernel.org

Hi Andy,

thanks a lot for your valuable reviews!

On Tue, Feb 11, 2020 at 02:18:52PM -0800, Andy Lutomirski wrote:
> On Tue, Feb 11, 2020 at 5:53 AM Joerg Roedel <joro@8bytes.org> wrote:
> > +       entry.offset_low    = (u16)(address & 0xffff);
> > +       entry.segment       = __KERNEL_CS;
> > +       entry.bits.type     = GATE_TRAP;
> 
> ^^^
> 
> I realize we're not running a real kernel here, but GATE_TRAP is
> madness.  Please use GATE_INTERRUPT.

Changed that.

> > +       /* Build pt_regs */
> > +       .if \error_code == 0
> > +       pushq   $0
> > +       .endif
> 
> cld

Added.

> > +       popq    %rdi
> 
> if error_code?

The code above pushes a $0 for exceptions without an error code, so it
needs to be removed unconditionally.

> > +
> > +       /* Remove error code and return */
> > +       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)
> > +
> 
> If this actually happens, you have a major bug.  Please sanitize all
> the segment registers after installing the GDT rather than hacking
> around it here.

Okay, will change that. I thought I could safe some instructions in the
head_64.S code, but you are right that its better to setup a defined
environment first.


Thanks,

	Joerg