linux-kernel - Re: [PATCH v4 0/4] arm64: drop pfn_valid_within() and simplify pfn

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YJuE5O8nWNc1TGZ6@linux.ibm.com>
Date:   Wed, 12 May 2021 10:33:56 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        David Hildenbrand <david@...hat.com>,
        Marc Zyngier <maz@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>,
        kvmarm <kvmarm@...ts.cs.columbia.edu>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH v4 0/4] arm64: drop pfn_valid_within() and simplify
 pfn_valid()

On Wed, May 12, 2021 at 09:00:02AM +0200, Ard Biesheuvel wrote:
> On Tue, 11 May 2021 at 12:05, Mike Rapoport <rppt@...nel.org> wrote:
> >
> > From: Mike Rapoport <rppt@...ux.ibm.com>
> >
> > Hi,
> >
> > These patches aim to remove CONFIG_HOLES_IN_ZONE and essentially hardwire
> > pfn_valid_within() to 1.
> >
> > The idea is to mark NOMAP pages as reserved in the memory map and restore
> > the intended semantics of pfn_valid() to designate availability of struct
> > page for a pfn.
> >
> > With this the core mm will be able to cope with the fact that it cannot use
> > NOMAP pages and the holes created by NOMAP ranges within MAX_ORDER blocks
> > will be treated correctly even without the need for pfn_valid_within.
> >
> > The patches are boot tested on qemu-system-aarch64.
> >
> 
> Did you use EFI boot when testing this? The memory map is much more
> fragmented in that case, so this would be a good data point.

Right, something like this:

[    0.000000] Early memory node ranges                                         
[    0.000000]   node   0: [mem 0x0000000040000000-0x00000000ffffbfff]          
[    0.000000]   node   0: [mem 0x00000000ffffc000-0x00000000ffffffff]          
[    0.000000]   node   0: [mem 0x0000000100000000-0x00000004386fffff]          
[    0.000000]   node   0: [mem 0x0000000438700000-0x000000043899ffff]          
[    0.000000]   node   0: [mem 0x00000004389a0000-0x00000004389bffff]          
[    0.000000]   node   0: [mem 0x00000004389c0000-0x0000000438b5ffff]          
[    0.000000]   node   0: [mem 0x0000000438b60000-0x000000043be3ffff]          
[    0.000000]   node   0: [mem 0x000000043be40000-0x000000043becffff]          
[    0.000000]   node   0: [mem 0x000000043bed0000-0x000000043bedffff]          
[    0.000000]   node   0: [mem 0x000000043bee0000-0x000000043bffffff]          
[    0.000000]   node   0: [mem 0x000000043c000000-0x000000043fffffff]          

This is a pity really, because I don't see a fundamental reason for those
tiny holes all over the place. 

I know that EFI/ACPI mandates "IO style" memory access for those regions,
but I fail to get why...
 
> > I beleive it would be best to route these via mmotm tree.
> >
> > v4:
> > * rebase on v5.13-rc1
> >
> > v3: Link: https://lore.kernel.org/lkml/20210422061902.21614-1-rppt@kernel.org
> > * Fix minor issues found by Anshuman
> > * Freshen up the declaration of pfn_valid() to make it consistent with
> >   pfn_is_map_memory()
> > * Add more Acked-by and Reviewed-by tags, thanks Anshuman and David
> >
> > v2: Link: https://lore.kernel.org/lkml/20210421065108.1987-1-rppt@kernel.org
> > * Add check for PFN overflow in pfn_is_map_memory()
> > * Add Acked-by and Reviewed-by tags, thanks David.
> >
> > v1: Link: https://lore.kernel.org/lkml/20210420090925.7457-1-rppt@kernel.org
> > * Add comment about the semantics of pfn_valid() as Anshuman suggested
> > * Extend comments about MEMBLOCK_NOMAP, per Anshuman
> > * Use pfn_is_map_memory() name for the exported wrapper for
> >   memblock_is_map_memory(). It is still local to arch/arm64 in the end
> >   because of header dependency issues.
> >
> > rfc: Link: https://lore.kernel.org/lkml/20210407172607.8812-1-rppt@kernel.org
> >
> > Mike Rapoport (4):
> >   include/linux/mmzone.h: add documentation for pfn_valid()
> >   memblock: update initialization of reserved pages
> >   arm64: decouple check whether pfn is in linear map from pfn_valid()
> >   arm64: drop pfn_valid_within() and simplify pfn_valid()
> >
> >  arch/arm64/Kconfig              |  3 ---
> >  arch/arm64/include/asm/memory.h |  2 +-
> >  arch/arm64/include/asm/page.h   |  3 ++-
> >  arch/arm64/kvm/mmu.c            |  2 +-
> >  arch/arm64/mm/init.c            | 14 +++++++++++++-
> >  arch/arm64/mm/ioremap.c         |  4 ++--
> >  arch/arm64/mm/mmu.c             |  2 +-
> >  include/linux/memblock.h        |  4 +++-
> >  include/linux/mmzone.h          | 11 +++++++++++
> >  mm/memblock.c                   | 28 ++++++++++++++++++++++++++--
> >  10 files changed, 60 insertions(+), 13 deletions(-)
> >
> >
> > base-commit: 6efb943b8616ec53a5e444193dccf1af9ad627b5
> > --
> > 2.28.0
> >

-- 
Sincerely yours,
Mike.