linux-kernel - Re: [RFC GIT PULL] EFI fixes, memblock quirk

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Date:   Tue, 19 Feb 2019 16:29:30 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Tejun Heo <tj@...nel.org>, Yinghai Lu <yinghai@...nel.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Tang Chen <tangchen@...fujitsu.com>,
        Alexander Kuleshov <kuleshovmail@...il.com>
Subject: Re: [RFC GIT PULL] EFI fixes, memblock quirk

On Tue, 19 Feb 2019 at 16:16, Ingo Molnar <mingo@...nel.org> wrote:
>
>
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>
> > On Sun, Feb 17, 2019 at 2:59 AM Ingo Molnar <mingo@...nel.org> wrote:
> > >
> > > I marked it RFC: please have a second look at the mm/memblock.c change,
> > > which adds a INIT_MEMBLOCK_RESERVED_REGIONS detour that ARM64 takes for
> > > these systems.
> >
> > It's not pretty, but it looks minimal for now. Pulled.
>
> Thanks!
>
> > > Perhaps we should upgrade the build time sizing of all platforms to
> > > INIT_MEMBLOCK_REGIONS+NR_CPUS+1 and thus centrally give an extra
> > > allocation entry per CPU configured?
> > >
> > > Or is there some cleaner solution?
> >
> > Is there some reason other platforms might want that kind of thing?
>
> Not that I'm aware of.
>

Nor me.

> > If not, then the current hack seems sufficient.
>
> Ok!
>

Thanks. It's a bit of a hack indeed, but every other option I explored
was a lot nastier. We might be able to tweak the LPI table allocation
logic so that they are adjacent, taking up only a single slot in the
reservation table, but that will have to wait for v5.2