linux-kernel - Re: [PATCH 5/5] RISC-V: Implement sparsemem

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Date:   Wed, 10 Oct 2018 17:27:29 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     logang@...tatee.com
CC:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-riscv@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-sh@...r.kernel.org,
        sbates@...thlin.com, aou@...s.berkeley.edu,
        Christoph Hellwig <hch@....de>, logang@...tatee.com,
        Andrew Waterman <andrew@...ive.com>,
        Olof Johansson <olof@...om.net>,
        Michael Clark <michaeljclark@....com>, robh@...nel.org,
        zong@...estech.com
Subject:     Re: [PATCH 5/5] RISC-V: Implement sparsemem

On Fri, 05 Oct 2018 09:16:42 PDT (-0700), logang@...tatee.com wrote:
> This patch implements sparsemem support for risc-v which helps pave the
> way for memory hotplug and eventually P2P support.
>
> We introduce Kconfig options for virtual and physical address bits which
> are used to calculate the size of the vmemmap and set the
> MAX_PHYSMEM_BITS.
>
> The vmemmap is located directly before the VMALLOC region and sized
> such that we can allocate enough pages to populate all the virtual
> address space in the system (similar to the way it's done in arm64).
>
> During initialization, call memblocks_present() and sparse_init(),
> and provide a stub for vmemmap_populate() (all of which is similar to
> arm64).
>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Cc: Palmer Dabbelt <palmer@...ive.com>
> Cc: Albert Ou <aou@...s.berkeley.edu>
> Cc: Andrew Waterman <andrew@...ive.com>
> Cc: Olof Johansson <olof@...om.net>
> Cc: Michael Clark <michaeljclark@....com>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Zong Li <zong@...estech.com>
> ---
>  arch/riscv/Kconfig                 | 23 +++++++++++++++++++++++
>  arch/riscv/include/asm/pgtable.h   | 24 ++++++++++++++++++++----
>  arch/riscv/include/asm/sparsemem.h | 11 +++++++++++
>  arch/riscv/kernel/setup.c          |  4 +++-
>  arch/riscv/mm/init.c               |  8 ++++++++
>  5 files changed, 65 insertions(+), 5 deletions(-)
>  create mode 100644 arch/riscv/include/asm/sparsemem.h

I don't really know anything about this, but you're welcome to add a

Reviewed-by: Palmer Dabbelt <palmer@...ive.com>

if you think it'll help.  I'm assuming you're targeting a different tree for 
the patch set, in which case it's probably best to keep this together with the 
rest of it.

Thanks for porting your stuff to RISC-V!

> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index a344980287a5..a1b5d758a542 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -52,12 +52,32 @@ config ZONE_DMA32
>  	bool
>  	default y if 64BIT
>
> +config VA_BITS
> +	int
> +	default 32 if 32BIT
> +	default 39 if 64BIT
> +
> +config PA_BITS
> +	int
> +	default 34 if 32BIT
> +	default 56 if 64BIT
> +
>  config PAGE_OFFSET
>  	hex
>  	default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
>  	default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
>  	default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
>
> +config ARCH_FLATMEM_ENABLE
> +	def_bool y
> +
> +config ARCH_SPARSEMEM_ENABLE
> +	def_bool y
> +	select SPARSEMEM_VMEMMAP_ENABLE
> +
> +config ARCH_SELECT_MEMORY_MODEL
> +	def_bool ARCH_SPARSEMEM_ENABLE
> +
>  config STACKTRACE_SUPPORT
>  	def_bool y
>
> @@ -92,6 +112,9 @@ config PGTABLE_LEVELS
>  config HAVE_KPROBES
>  	def_bool n
>
> +config HAVE_ARCH_PFN_VALID
> +	def_bool y
> +
>  menu "Platform type"
>
>  choice
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index 16301966d65b..20c49cded686 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -89,6 +89,26 @@ extern pgd_t swapper_pg_dir[];
>  #define __S110	PAGE_SHARED_EXEC
>  #define __S111	PAGE_SHARED_EXEC
>
> +#define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
> +#define VMALLOC_END      (PAGE_OFFSET - 1)
> +#define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
> +
> +/*
> + * Log2 of the upper bound of the size of a struct page. Used for sizing
> + * the vmemmap region only, does not affect actual memory footprint.
> + * We don't use sizeof(struct page) directly since taking its size here
> + * requires its definition to be available at this point in the inclusion
> + * chain, and it may not be a power of 2 in the first place.
> + */
> +#define STRUCT_PAGE_MAX_SHIFT	6
> +
> +#define VMEMMAP_SIZE	(UL(1) << (CONFIG_VA_BITS - PAGE_SHIFT - 1 + \
> +				   STRUCT_PAGE_MAX_SHIFT))
> +#define VMEMMAP_END	(VMALLOC_START - 1)
> +#define VMEMMAP_START	(VMALLOC_START - VMEMMAP_SIZE)
> +
> +#define vmemmap		((struct page *)VMEMMAP_START)
> +
>  /*
>   * ZERO_PAGE is a global shared page that is always zero,
>   * used for zero-mapped memory areas, etc.
> @@ -411,10 +431,6 @@ static inline void pgtable_cache_init(void)
>  	/* No page table caches to initialize */
>  }
>
> -#define VMALLOC_SIZE     (KERN_VIRT_SIZE >> 1)
> -#define VMALLOC_END      (PAGE_OFFSET - 1)
> -#define VMALLOC_START    (PAGE_OFFSET - VMALLOC_SIZE)
> -
>  /*
>   * Task size is 0x40000000000 for RV64 or 0xb800000 for RV32.
>   * Note that PGDIR_SIZE must evenly divide TASK_SIZE.
> diff --git a/arch/riscv/include/asm/sparsemem.h b/arch/riscv/include/asm/sparsemem.h
> new file mode 100644
> index 000000000000..4563e806c788
> --- /dev/null
> +++ b/arch/riscv/include/asm/sparsemem.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __ASM_SPARSEMEM_H
> +#define __ASM_SPARSEMEM_H
> +
> +#ifdef CONFIG_SPARSEMEM
> +#define MAX_PHYSMEM_BITS	CONFIG_PA_BITS
> +#define SECTION_SIZE_BITS	30
> +#endif
> +
> +#endif
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index aee603123030..89fa781a9bf8 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -205,6 +205,9 @@ static void __init setup_bootmem(void)
>  		                  PFN_PHYS(end_pfn - start_pfn),
>  		                  &memblock.memory, 0);
>  	}
> +
> +	memblocks_present();
> +	sparse_init();
>  }
>
>  void __init setup_arch(char **cmdline_p)
> @@ -239,4 +242,3 @@ void __init setup_arch(char **cmdline_p)
>
>  	riscv_fill_hwcap();
>  }
> -
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 58a522f9bcc3..5d529878667c 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -70,3 +70,11 @@ void free_initrd_mem(unsigned long start, unsigned long end)
>  {
>  }
>  #endif /* CONFIG_BLK_DEV_INITRD */
> +
> +#ifdef CONFIG_SPARSEMEM
> +int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
> +			       struct vmem_altmap *altmap)
> +{
> +	return vmemmap_populate_basepages(start, end, node);
> +}
> +#endif