linux-kernel - Re: [PATCH v2 08/22] memblock: Introduce a generic phys_addr_to_target

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Message-ID: <CAPcyv4iRJRz==VRgq=M_FYz0TfNKqKASOD1+NRfMLcHzEOBApQ@mail.gmail.com>
Date:   Mon, 13 Jul 2020 08:48:27 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Jia He <justin.he@....com>, Will Deacon <will@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Christoph Hellwig <hch@....de>,
        Joao Martins <joao.m.martins@...cle.com>
Subject: Re: [PATCH v2 08/22] memblock: Introduce a generic phys_addr_to_target_node()

On Mon, Jul 13, 2020 at 12:04 AM Mike Rapoport <rppt@...ux.ibm.com> wrote:
>
> Hi Dan,
>
> On Sun, Jul 12, 2020 at 09:26:48AM -0700, Dan Williams wrote:
> > Similar to how generic memory_add_physaddr_to_nid() interrogates
> > memblock data for numa information, introduce
> > get_reserved_pfn_range_from_nid() to enable the same operation for
> > reserved memory ranges. Example memory ranges that are reserved, but
> > still have associated numa-info are persistent memory or Soft Reserved
> > (EFI_MEMORY_SP) memory.
>
> Here again, I would prefer to add a weak default for
> phys_to_target_node() because the "generic" implementation is not really
> generic.
>
> The fallback to reserved ranges is x86 specfic because on x86 most of the
> reserved areas is not in memblock.memory. AFAIK, no other architecture
> does this.

True, I was pre-fetching ARM using the new EFI "Special Purpose"
memory attribute. However, until that becomes something that platforms
deploy in practice I'm ok with not solving that problem for now.

> And x86 anyway has implementation of phys_to_target_node().

Sure, let's go with the default stub for non-x86.

Justin, do you think it would make sense to fold your dax_kmem
enabling for arm64 series into my enabling of dax_hmem for all
memory-hotplug archs?