linux-kernel - Re: [tip:efi/core] x86/efi: Unmap EFI boot services code/data regions from efi

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Message-ID: <20190107155356.GA7578@codeblueprint.co.uk>
Date:   Mon, 7 Jan 2019 15:57:52 +0000
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Borislav Petkov <bp@...en8.de>,
        "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>,
        Ingo Molnar <mingo@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>,
        "marc.zyngier@....com" <marc.zyngier@....com>,
        "eric.snowberg@...cle.com" <eric.snowberg@...cle.com>,
        "hdegoede@...hat.com" <hdegoede@...hat.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "arend.vanspriel@...adcom.com" <arend.vanspriel@...adcom.com>,
        "julien.thierry@....com" <julien.thierry@....com>,
        "bhsharma@...hat.com" <bhsharma@...hat.com>,
        "jonathanh@...dia.com" <jonathanh@...dia.com>,
        "joe@...ches.com" <joe@...ches.com>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        "natechancellor@...il.com" <natechancellor@...il.com>,
        "luto@...nel.org" <luto@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "sedat.dilek@...il.com" <sedat.dilek@...il.com>,
        "zhuyifei1999@...il.com" <zhuyifei1999@...il.com>,
        "linux-tip-commits@...r.kernel.org" 
        <linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:efi/core] x86/efi: Unmap EFI boot services code/data
 regions from efi_pgd

On Sat, 22 Dec, at 12:07:48PM, Ard Biesheuvel wrote:
> On Fri, 21 Dec 2018 at 20:29, Borislav Petkov <bp@...en8.de> wrote:
> >
> > On Fri, Dec 21, 2018 at 06:26:23PM +0100, Ard Biesheuvel wrote:
> > > On Fri, 21 Dec 2018 at 18:13, Borislav Petkov <bp@...en8.de> wrote:
> > > >
> > > > On Fri, Dec 21, 2018 at 06:02:29PM +0100, Ard Biesheuvel wrote:
> > > > > As far as I can tell, the SGI x86 UV platforms still rely on this, so
> > > > > we're stuck with it for the foreseeable future.
> > > >
> > > > What happened with the old apple laptops which couldn't handle high
> > > > virtual mappings and needed 1:1? We don't care anymore?
> > > >
> > >
> > > If that is the case (I wouldn't know) then yes, there is a second
> > > reason why we need to keep this code.
> >
> > Fleming knows details and he's on CC, lemme "pull" him up into To: :-)
> >
> 
> IIUC the 1:1 mapping and the 'old' mapping are two different things,
> and the new mapping also contains a 1:1 mapping of the boot services
> regions, at least until SetVirtualAddressMap() returns.

Yep, they're different. And yes the 1:1 mapping should stick around
with the new scheme IIRC (it's been a while).