linux-kernel - Re: [PATCH v7 00/12] EFI Specific Purpose Memory Support

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Date:   Wed, 16 Oct 2019 08:33:56 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Andy Shevchenko <andy@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Keith Busch <kbusch@...nel.org>, Len Brown <lenb@...nel.org>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Darren Hart <dvhart@...radead.org>,
        Dave Jiang <dave.jiang@...el.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        kbuild test robot <lkp@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Andy Lutomirski <luto@...nel.org>,
        linux-efi <linux-efi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v7 00/12] EFI Specific Purpose Memory Support

On Tue, Oct 15, 2019 at 11:55 PM Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
>
> On Wed, 16 Oct 2019 at 03:13, Dan Williams <dan.j.williams@...el.com> wrote:
> >
> > Changes since v6 [1]:
> > - Collect Ard's ack / review on patches 5-7, but not on patch 4 since it
> >   needed a non-trivial rework for linker error reported by the 0day robot.
> >
> > - Fixup "efi: Common enable/disable infrastructure for EFI soft
> >   reservation" with a new dependency on CONFIG_EFI_STUB for
> >   CONFIG_EFI_SOFT_RESERVE since the efi_soft_reserve_enabled() helper is
> >   only built with EFI_STUB=y and the support depends on early reservations
> >   to keep the kernel text from landing in the reservation.
>
> As far as I know, GRUB on x86 still boots without the EFI stub by
> default (i.e., using the 'linux' command instead of the 'linuxefi'
> command), so even if you build the stub, it is not going to be called
> in many cases. Is that going to be a problem?

It only becomes a problem if kaslr decides to land the kernel on top
of the soft-reservation. However, I think it's ok to say that if you
need the reservation to be honored in all circumstances, arrange to
boot in EFI mode.

>
> > This also
> >   moved the IS_ENABLED(CONFIG_EFI_SOFT_RESERVE) check into the header so
> >   that the stub does not try to link to __efi_soft_reserve_enabled() in
> >   the EFI_STUB=n case.
> >
> > - Rework "x86/efi: EFI soft reservation to E820 enumeration" to always
> >   add the full EFI memory map when EFI_MEMORY_SP ranges are found. This
> >   simplifies the logic to just add the full EFI map rather than try to
> >   tease out just the EFI_MEMORY_SP ranges. (Ard)
> >
> > [1]: https://lore.kernel.org/lkml/157066227329.1059972.5659620631541203458.stgit@dwillia2-desk3.amr.corp.intel.com/
> >
> > ---
> > Merge notes:
> >
> > Hi Ingo,
> >
> > I'm still looking for Ard's ack on the revised patch 4, but otherwise
> > feel like this is ready for your consideration.
> >
>
> Patch 4 looks fine to me,
>
> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>

Thanks for the help.