Re: [PATCH v6] RISC-V: Implement sparsemem

[Mike Rapoport]

On Wed, Aug 28, 2019 at 03:40:54PM -0600, Logan Gunthorpe wrote:
> Implement sparsemem support for Risc-v which helps pave the
> way for memory hotplug and eventually P2P support.
> 
> 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).
> 
> [greentime.hu@xxxxxxxxxx:
>   fixed pfn_valid, FIXADDR_TOP and fixed a bug rebasing onto v5.3]
> Signed-off-by: Greentime Hu <greentime.hu@xxxxxxxxxx>
> Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> Reviewed-by: Palmer Dabbelt <palmer@xxxxxxxxxx>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Cc: Albert Ou <aou@xxxxxxxxxxxxxxxxx>
> Cc: Andrew Waterman <andrew@xxxxxxxxxx>
> Cc: Olof Johansson <olof@xxxxxxxxx>
> Cc: Michael Clark <michaeljclark@xxxxxxx>
> Cc: Rob Herring <robh@xxxxxxxxxx>
> Cc: Zong Li <zong@xxxxxxxxxxxxx>

Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>

> ---
>  arch/riscv/Kconfig                 | 21 +++++++++++++++++++++
>  arch/riscv/include/asm/fixmap.h    |  2 +-
>  arch/riscv/include/asm/page.h      |  2 ++
>  arch/riscv/include/asm/pgtable.h   | 21 +++++++++++++++++----
>  arch/riscv/include/asm/sparsemem.h | 11 +++++++++++
>  arch/riscv/mm/init.c               | 10 ++++++++++
>  6 files changed, 62 insertions(+), 5 deletions(-)
>  create mode 100644 arch/riscv/include/asm/sparsemem.h
> 
> Changes in v6:
>  * Rebased onto v5.3-rc6 (no changes)
>  * Fixed up commit message wording (per Mike's feedback)
>  * Set SPARSEMEM_STATIC for 32BIT builds (per Mike)
> 
> Changes in v5:
>  * Rebased onto v5.3-rc5 (required moving the initialization to
>    after setup_vm_final() in paging_init())
>  * Fixed FIXADDR_TOP value (per Greentime)
>  * Use generic pfn_valid() function for sparsemem to fix a bug
>    with having holes in memory (also Greentime)
> 
> Changes in v4:
>  * Rebased onto v5.0-rc1
>  * Changed the SECTION_SIZE_BITS to 27, per Nick Kossifidis
> 
> Changes in v3 (only sent the common patches):
>  * Rebased on v4.20-rc1
>  * Minor fixups
>  * Collected Ack from Will Deacon
> 
> Changes in v2:
>  * Rebase on v4.19-rc8
>  * Move the STRUCT_PAGE_MAX_SHIFT define into a common header (near
>    the definition of struct page). As suggested by Christoph.
>  * Clean up the unnecessary nid variable in the memblocks_present()
>    function, per Christoph.
>  * Collected tags from Palmer and Catalin.
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 59a4727ecd6c..53b7556beb4a 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -54,6 +54,7 @@ config RISCV
>  	select EDAC_SUPPORT
>  	select ARCH_HAS_GIGANTIC_PAGE
>  	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
> +	select SPARSEMEM_STATIC if 32BIT
> 
>  config MMU
>  	def_bool y
> @@ -62,12 +63,32 @@ 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 ARCH_WANT_GENERAL_HUGETLB
>  	def_bool y
> 
> diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
> index 9c66033c3a54..7b0259c044c9 100644
> --- a/arch/riscv/include/asm/fixmap.h
> +++ b/arch/riscv/include/asm/fixmap.h
> @@ -31,7 +31,7 @@ enum fixed_addresses {
>  };
> 
>  #define FIXADDR_SIZE		(__end_of_fixed_addresses * PAGE_SIZE)
> -#define FIXADDR_TOP		(VMALLOC_START)
> +#define FIXADDR_TOP		(VMEMMAP_START)
>  #define FIXADDR_START		(FIXADDR_TOP - FIXADDR_SIZE)
> 
>  #define FIXMAP_PAGE_IO		PAGE_KERNEL
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index 707e00a8430b..3db261c4810f 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -110,8 +110,10 @@ extern unsigned long min_low_pfn;
>  #define page_to_bus(page)	(page_to_phys(page))
>  #define phys_to_page(paddr)	(pfn_to_page(phys_to_pfn(paddr)))
> 
> +#ifdef CONFIG_FLATMEM
>  #define pfn_valid(pfn) \
>  	(((pfn) >= pfn_base) && (((pfn)-pfn_base) < max_mapnr))
> +#endif
> 
>  #define ARCH_PFN_OFFSET		(pfn_base)
> 
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index a364aba23d55..dbc19e61ee66 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -83,6 +83,23 @@ 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)
> +
> +/*
> + * Roughly size the vmemmap space to be large enough to fit enough
> + * struct pages to map half the virtual address space. Then
> + * position vmemmap directly below the VMALLOC region.
> + */
> +#define VMEMMAP_SHIFT \
> +	(CONFIG_VA_BITS - PAGE_SHIFT - 1 + STRUCT_PAGE_MAX_SHIFT)
> +#define VMEMMAP_SIZE	(1UL << VMEMMAP_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.
> @@ -416,10 +433,6 @@ 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 0x4000000000 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..b58ba2d9ed6e
> --- /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	27
> +#endif /* CONFIG_SPARSEMEM */
> +
> +#endif /* __ASM_SPARSEMEM_H */
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 42bf939693d3..73f40c9d3dee 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -442,6 +442,16 @@ static void __init setup_vm_final(void)
>  void __init paging_init(void)
>  {
>  	setup_vm_final();
> +	memblocks_present();
> +	sparse_init();
>  	setup_zero_page();
>  	zone_sizes_init();
>  }
> +
> +#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
> --
> 2.20.1
> 
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-- 
Sincerely yours,
Mike.