From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>,
Reza Arbab <arbab@linux.vnet.ibm.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Dan Williams <dan.j.williams@intel.com>,
Balbir Singh <bsingharora@gmail.com>,
Gavin Shan <gwshan@linux.vnet.ibm.com>,
David Gibson <david@gibson.dropbear.id.au>,
Vasant Hegde <hegdevasant@linux.vnet.ibm.com>,
Scott Wood <scottwood@freescale.com>,
"Oliver O'Halloran" <oohall@gmail.com>,
Nathan Fontenot <nfont@linux.vnet.ibm.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/mm: update arch_{add,remove}_memory() for radix
Date: Tue, 28 Jun 2016 19:33:06 +0530 [thread overview]
Message-ID: <87ziq54did.fsf@skywalker.in.ibm.com> (raw)
In-Reply-To: <1467112865.16036.4.camel@ellerman.id.au>
Michael Ellerman <mpe@ellerman.id.au> writes:
> On Thu, 2016-06-23 at 14:37 -0500, Reza Arbab wrote:
>> On Thu, Jun 23, 2016 at 10:47:20PM +0530, Aneesh Kumar K.V wrote:
>> > Reza Arbab <arbab@linux.vnet.ibm.com> writes:
>> > > These functions are making direct calls to the hash table APIs,
>> > > leading to a BUG() on systems using radix.
>> > >
>> > > Switch them to the vmemmap_{create,remove}_mapping() wrappers, and
>> > > move to the __meminit section.
>> >
>> > They are really not the same. They can possibly end up using different
>> > base page size. Also vmemmap is available only with SPARSEMEM_VMEMMAP
>> > enabled. Does hotplug depend on sparsemem vmemmap ?
>>
>> I'm not sure. Maybe it's best if I back up a step and explain what lead
>> me to this patch. During hotplug, you get
>>
>> ...
>> arch_add_memory
>> create_section_mapping
>> htab_bolt_mapping
>> BUG_ON(!ppc_md.hpte_insert);
>>
>> So it seemed to me that I needed a radix equivalent of
>> create_section_mapping().
>>
>> After some digging, I found hash__vmemmap_create_mapping() and
>> radix__vmemmap_create_mapping() did what I needed. I did not notice the
>> #ifdef SPARSEMEM_VMEMMAP around them.
>
> I think that's more by luck than design. The vmemmap routines use
> mmu_vmemmap_psize which is probably but not definitely the same as
> mmu_linear_psize.
>
>> Could it be that the functions just need to be renamed
>> hash__create_mapping()/radix__create_mapping() and moved out of #ifdef
>> SPARSEMEM_VMEMMAP?
>
> No, you need to use mmu_linear_psize for the hotplug case.
>
> But you can probably factor out a common routine that both cases use, and hide
> the hash vs radix check in that.
>
> And probably send me a patch to make MEMORY_HOTPLUG depend on !RADIX for v4.7?
Few other stuff we need to still look from Radix point
1) machine check handling/memory errors
2) kexec
-aneesh
next prev parent reply other threads:[~2016-06-28 14:08 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-23 16:39 [PATCH] powerpc/mm: update arch_{add,remove}_memory() for radix Reza Arbab
2016-06-23 17:17 ` Aneesh Kumar K.V
2016-06-23 19:37 ` Reza Arbab
2016-06-23 19:52 ` Reza Arbab
2016-06-28 11:21 ` Michael Ellerman
2016-06-28 14:03 ` Aneesh Kumar K.V [this message]
2016-06-29 15:37 ` Reza Arbab
2016-06-24 3:22 ` Balbir Singh
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