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

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Message-ID: <CAKv+Gu9iJinkP-buhmzRyB91_HcJ-tDwT3YHeHGFo4Bsiv7O_Q@mail.gmail.com>
Date:   Mon, 17 Dec 2018 20:35:37 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
        "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>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
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        "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 Mon, 17 Dec 2018 at 19:42, Prakhya, Sai Praneeth
<sai.praneeth.prakhya@...el.com> wrote:
>
> > > Hi Thomas and Ingo,
> > >
> > > I recently noticed that the below commits [1] and [2] are broken when
> > > kernel command line argument "efi=old_map" is passed. Sorry! I missed
> > > to test this condition prior to sending these patches to mailing list.
> > > I am working on a fix and will send it to mailing list as soon as it's ready.
> > >
> >
> > Could you elaborate on the problem please?
>
> Sure! My bad..
>
> Little bit of history here:
> Boris with this patch set [1] introduced statically mapping EFI Runtime Services at -4G
> and also introduced "efi=old_map" to return to previous EFI functionality which used
> ioremap and __va(pa).
>
> [3] and [4] are links to old_map_region()
>
> The commit 08cfb38f3ef4 ("x86/efi: Unmap EFI boot services code/data regions from efi_pgd"),
> unmaps EFI boot services code/data regions *only* from efi_pgd but efi=old_map maps
> EFI boot services code/data regions into swapper_pgd. Also, efi=old_map  uses either
> ioremap() or __va(md->phys_addr) to map EFI runtime/boot time services and doesn't use kernel_map_pages_in_pgd().
>
> So, we need a different unmapping routine to unmap EFI boot services code/data
> regions from swapper_pgd if they were mapped using efi=old_map.
>

For the short term, could we simply make your changes dependent on efi
!= old_map? That gives us some time to fix the old_map case properly.