linux-kernel - Re: [PATCH V3 (RESEND) 1/3] mm/sparsemem: Enable vmem_altmap support in vmemmap_populate

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Date:   Thu, 2 Jul 2020 15:03:55 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Tony Luck <tony.luck@...el.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michal Hocko <mhocko@...e.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        linux-arm-kernel@...ts.infradead.org, linux-ia64@...r.kernel.org,
        linux-riscv@...ts.infradead.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V3 (RESEND) 1/3] mm/sparsemem: Enable vmem_altmap support
 in vmemmap_populate_basepages()

On Thu, Jun 18, 2020 at 06:45:28AM +0530, Anshuman Khandual wrote:
> vmemmap_populate_basepages() is used across platforms to allocate backing
> memory for vmemmap mapping. This is used as a standard default choice or
> as a fallback when intended huge pages allocation fails. This just creates
> entire vmemmap mapping with base pages (PAGE_SIZE).
> 
> On arm64 platforms, vmemmap_populate_basepages() is called instead of the
> platform specific vmemmap_populate() when ARM64_SWAPPER_USES_SECTION_MAPS
> is not enabled as in case for ARM64_16K_PAGES and ARM64_64K_PAGES configs.
> 
> At present vmemmap_populate_basepages() does not support allocating from
> driver defined struct vmem_altmap while trying to create vmemmap mapping
> for a device memory range. It prevents ARM64_16K_PAGES and ARM64_64K_PAGES
> configs on arm64 from supporting device memory with vmemap_altmap request.
> 
> This enables vmem_altmap support in vmemmap_populate_basepages() unlocking
> device memory allocation for vmemap mapping on arm64 platforms with 16K or
> 64K base page configs.
> 
> Each architecture should evaluate and decide on subscribing device memory
> based base page allocation through vmemmap_populate_basepages(). Hence lets
> keep it disabled on all archs in order to preserve the existing semantics.
> A subsequent patch enables it on arm64.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Paul Walmsley <paul.walmsley@...ive.com>
> Cc: Palmer Dabbelt <palmer@...belt.com>
> Cc: Tony Luck <tony.luck@...el.com>
> Cc: Fenghua Yu <fenghua.yu@...el.com>
> Cc: Dave Hansen <dave.hansen@...ux.intel.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-ia64@...r.kernel.org
> Cc: linux-riscv@...ts.infradead.org
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> Tested-by: Jia He <justin.he@....com>
> Acked-by: Will Deacon <will@...nel.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>

For arm64:

Acked-by: Catalin Marinas <catalin.marinas@....com>