linux-kernel - Re: [PATCH] x86/boot/64: Initialize 5-level paging variables earlier

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Message-ID: <20201012153501.GA559681@rani.riverdale.lan>
Date:   Mon, 12 Oct 2020 11:35:01 -0400
From:   Arvind Sankar <nivedita@...m.mit.edu>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     Arvind Sankar <nivedita@...m.mit.edu>, x86@...nel.org,
        Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...en8.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/boot/64: Initialize 5-level paging variables earlier

On Mon, Oct 12, 2020 at 05:08:30PM +0300, Kirill A. Shutemov wrote:
> On Sat, Oct 10, 2020 at 03:26:24PM -0400, Arvind Sankar wrote:
> > On Sat, Oct 10, 2020 at 03:11:10PM -0400, Arvind Sankar wrote:
> > > Commit
> > >   ca0e22d4f011 ("x86/boot/compressed/64: Always switch to own page table")
> > > started using a new set of pagetables even without KASLR.
> > > 
> > > After that commit, initialize_identity_maps() is called before the
> > > 5-level paging variables are setup in choose_random_location(), which
> > > will not work if 5-level paging is actually enabled.
> > 
> > Note that I don't have hardware that supports 5-level paging, so this
> > is not actually tested with 5-level, but based on code inspection, it
> > shouldn't work.
> 
> qemu supports it. -cpu "qemu64,+la57"
> 
> -- 
>  Kirill A. Shutemov

Thanks! On QEMU, it does crash without this patch.