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Date:   Tue, 27 Aug 2019 09:18:21 +0200
From:   Michal Hocko <mhocko@kernel.org>
To:     Alastair D'Silva <alastair@au1.ibm.com>
Cc:     Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Christophe Leroy <christophe.leroy@c-s.fr>,
        Andrew Morton <akpm@linux-foundation.org>,
        David Hildenbrand <david@redhat.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc: Perform a bounds check in arch_add_memory
Message-ID: <20190827071821.GS7538@dhcp22.suse.cz>
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On Tue 27-08-19 16:39:56, Alastair D'Silva wrote:
> On Tue, 2019-08-27 at 08:28 +0200, Michal Hocko wrote:
> > On Tue 27-08-19 15:20:46, Alastair D'Silva wrote:
> > > From: Alastair D'Silva <alastair@d-silva.org>
> > > 
> > > It is possible for firmware to allocate memory ranges outside
> > > the range of physical memory that we support (MAX_PHYSMEM_BITS).
> > 
> > Doesn't that count as a FW bug? Do you have any evidence of that in
> > the
> > field? Just wondering...
> > 
> 
> Not outside our lab, but OpenCAPI attached LPC memory is assigned
> addresses based on the slot/NPU it is connected to. These addresses
> prior to:
> 4ffe713b7587 ("powerpc/mm: Increase the max addressable memory to 2PB")
> were inaccessible and resulted in bogus sections - see our discussion
> on 'mm: Trigger bug on if a section is not found in __section_nr'.

Please document this in the changelog

-- 
Michal Hocko
SUSE Labs