[PATCH v2 0/6] sparsemem support for RISC-V

[PATCH v2 0/6] sparsemem support for RISC-V

[Logan Gunthorpe]

This patchset implements sparsemem on RISC-V. The first few patches
move some code in existing architectures into common helpers
so they can be used by the new RISC-V implementation. The final
patch actually adds sparsmem support to RISC-V.

This is the first small step in supporting P2P on RISC-V.

--

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.

--
Logan Gunthorpe (6):
  mm: Introduce common STRUCT_PAGE_MAX_SHIFT define
  mm/sparse: add common helper to mark all memblocks present
  ARM: mm: make use of new memblocks_present() helper
  arm64: mm: make use of new memblocks_present() helper
  sh: mm: make use of new memblocks_present() helper
  RISC-V: Implement sparsemem

 arch/arm/mm/init.c                 | 17 +----------------
 arch/arm64/include/asm/memory.h    |  9 ---------
 arch/arm64/mm/init.c               | 28 +---------------------------
 arch/riscv/Kconfig                 | 23 +++++++++++++++++++++++
 arch/riscv/include/asm/pgtable.h   | 21 +++++++++++++++++----
 arch/riscv/include/asm/sparsemem.h | 11 +++++++++++
 arch/riscv/kernel/setup.c          |  4 +++-
 arch/riscv/mm/init.c               |  8 ++++++++
 arch/sh/mm/init.c                  |  7 +------
 include/asm-generic/fixmap.h       |  1 +
 include/linux/mm_types.h           |  5 +++++
 include/linux/mmzone.h             |  6 ++++++
 mm/sparse.c                        | 14 ++++++++++++++
 13 files changed, 91 insertions(+), 63 deletions(-)
 create mode 100644 arch/riscv/include/asm/sparsemem.h

--
2.19.0

[PATCH v2 1/6] mm: Introduce common STRUCT_PAGE_MAX_SHIFT define

[Logan Gunthorpe]

This define is used by arm64 to calculate the size of the vmemmap
region. It is defined as the log2 of the upper bound on the size
of a struct page.

We move it into mm_types.h so it can be defined properly instead of
set and checked with a build bug. This also allows us to use the same
define for riscv.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
---
 arch/arm64/include/asm/memory.h | 9 ---------
 arch/arm64/mm/init.c            | 8 --------
 include/asm-generic/fixmap.h    | 1 +
 include/linux/mm_types.h        | 5 +++++
 4 files changed, 6 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h
index b96442960aea..f0a5c9531e8b 100644
--- a/arch/arm64/include/asm/memory.h
+++ b/arch/arm64/include/asm/memory.h
@@ -34,15 +34,6 @@
  */
 #define PCI_IO_SIZE		SZ_16M
 
-/*
- * 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
-
 /*
  * VMEMMAP_SIZE - allows the whole linear region to be covered by
  *                a struct page array
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 787e27964ab9..6a0b5c5a61af 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -615,14 +615,6 @@ void __init mem_init(void)
 	BUILD_BUG_ON(TASK_SIZE_32			> TASK_SIZE_64);
 #endif
 
-#ifdef CONFIG_SPARSEMEM_VMEMMAP
-	/*
-	 * Make sure we chose the upper bound of sizeof(struct page)
-	 * correctly when sizing the VMEMMAP array.
-	 */
-	BUILD_BUG_ON(sizeof(struct page) > (1 << STRUCT_PAGE_MAX_SHIFT));
-#endif
-
 	if (PAGE_SIZE >= 16384 && get_num_physpages() <= 128) {
 		extern int sysctl_overcommit_memory;
 		/*
diff --git a/include/asm-generic/fixmap.h b/include/asm-generic/fixmap.h
index 827e4d3bbc7a..8cc7b09c1bc7 100644
--- a/include/asm-generic/fixmap.h
+++ b/include/asm-generic/fixmap.h
@@ -16,6 +16,7 @@
 #define __ASM_GENERIC_FIXMAP_H
 
 #include <linux/bug.h>
+#include <linux/mm_types.h>
 
 #define __fix_to_virt(x)	(FIXADDR_TOP - ((x) << PAGE_SHIFT))
 #define __virt_to_fix(x)	((FIXADDR_TOP - ((x)&PAGE_MASK)) >> PAGE_SHIFT)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5ed8f6292a53..ec8c16d9396b 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -206,6 +206,11 @@ struct page {
 #endif
 } _struct_page_alignment;
 
+/*
+ * Used for sizing the vmemmap region on some architectures
+ */
+#define STRUCT_PAGE_MAX_SHIFT	ilog2(roundup_pow_of_two(sizeof(struct page)))
+
 #define PAGE_FRAG_CACHE_MAX_SIZE	__ALIGN_MASK(32768, ~PAGE_MASK)
 #define PAGE_FRAG_CACHE_MAX_ORDER	get_order(PAGE_FRAG_CACHE_MAX_SIZE)
 
-- 
2.19.0

Re: [PATCH v2 1/6] mm: Introduce common STRUCT_PAGE_MAX_SHIFT define

[Will Deacon]

Hi Logan,

On Mon, Oct 15, 2018 at 11:56:57AM -0600, Logan Gunthorpe wrote:
> This define is used by arm64 to calculate the size of the vmemmap
> region. It is defined as the log2 of the upper bound on the size
> of a struct page.
> 
> We move it into mm_types.h so it can be defined properly instead of
> set and checked with a build bug. This also allows us to use the same
> define for riscv.
> 
> Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Christoph Hellwig <hch@lst.de>
> ---
>  arch/arm64/include/asm/memory.h | 9 ---------
>  arch/arm64/mm/init.c            | 8 --------
>  include/asm-generic/fixmap.h    | 1 +
>  include/linux/mm_types.h        | 5 +++++
>  4 files changed, 6 insertions(+), 17 deletions(-)

This looks like a really good cleanup to me, thanks:

Acked-by: Will Deacon <will.deacon@arm.com>

Will

[PATCH v2 2/6] mm/sparse: add common helper to mark all memblocks present

[Logan Gunthorpe]

Presently the arches arm64, arm and sh have a function which loops through
each memblock and calls memory present. riscv will require a similar
function.

Introduce a common memblocks_present() function that can be used by
all the arches. Subsequent patches will cleanup the arches that
make use of this.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Pavel Tatashin <pasha.tatashin@oracle.com>
Cc: Oscar Salvador <osalvador@suse.de>
---
 include/linux/mmzone.h |  6 ++++++
 mm/sparse.c            | 14 ++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d4b0c79d2924..26a026a45857 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -784,6 +784,12 @@ void memory_present(int nid, unsigned long start, unsigned long end);
 static inline void memory_present(int nid, unsigned long start, unsigned long end) {}
 #endif
 
+#if defined(CONFIG_SPARSEMEM) && defined(CONFIG_HAVE_MEMBLOCK)
+void memblocks_present(void);
+#else
+static inline void memblocks_present(void) {}
+#endif
+
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
 int local_memory_node(int node_id);
 #else
diff --git a/mm/sparse.c b/mm/sparse.c
index 10b07eea9a6e..90aec8331a03 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -5,6 +5,7 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/mmzone.h>
+#include <linux/memblock.h>
 #include <linux/bootmem.h>
 #include <linux/compiler.h>
 #include <linux/highmem.h>
@@ -238,6 +239,19 @@ void __init memory_present(int nid, unsigned long start, unsigned long end)
 	}
 }
 
+#ifdef CONFIG_HAVE_MEMBLOCK
+void __init memblocks_present(void)
+{
+	struct memblock_region *reg;
+
+	for_each_memblock(memory, reg) {
+		memory_present(memblock_get_region_node(reg),
+			       memblock_region_memory_base_pfn(reg),
+			       memblock_region_memory_end_pfn(reg));
+	}
+}
+#endif
+
 /*
  * Subtle, we encode the real pfn into the mem_map such that
  * the identity pfn - section_mem_map will return the actual
-- 
2.19.0

[PATCH v2 3/6] ARM: mm: make use of new memblocks_present() helper

[Logan Gunthorpe]

Cleanup the arm_memory_present() function seeing it's very
similar to other arches.

The new memblocks_present() helper checks for node ids which the
arm version did not. However, this is equivalent seeing
HAVE_MEMBLOCK_NODE_MAP should be false in this arch and therefore
memblock_get_region_node() should return 0.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Philip Derrin <philip@cog.systems>
Cc: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
Cc: Nicolas Pitre <nicolas.pitre@linaro.org>
---
 arch/arm/mm/init.c | 17 +----------------
 1 file changed, 1 insertion(+), 16 deletions(-)

diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
index 0cc8e04295a4..e2710dd7446f 100644
--- a/arch/arm/mm/init.c
+++ b/arch/arm/mm/init.c
@@ -201,21 +201,6 @@ int pfn_valid(unsigned long pfn)
 EXPORT_SYMBOL(pfn_valid);
 #endif
 
-#ifndef CONFIG_SPARSEMEM
-static void __init arm_memory_present(void)
-{
-}
-#else
-static void __init arm_memory_present(void)
-{
-	struct memblock_region *reg;
-
-	for_each_memblock(memory, reg)
-		memory_present(0, memblock_region_memory_base_pfn(reg),
-			       memblock_region_memory_end_pfn(reg));
-}
-#endif
-
 static bool arm_memblock_steal_permitted = true;
 
 phys_addr_t __init arm_memblock_steal(phys_addr_t size, phys_addr_t align)
@@ -317,7 +302,7 @@ void __init bootmem_init(void)
 	 * Sparsemem tries to allocate bootmem in memory_present(),
 	 * so must be done after the fixed reservations
 	 */
-	arm_memory_present();
+	memblocks_present();
 
 	/*
 	 * sparse_init() needs the bootmem allocator up and running.
-- 
2.19.0

[PATCH v2 4/6] arm64: mm: make use of new memblocks_present() helper

[Logan Gunthorpe]

Cleanup the arm64_memory_present() function seeing it's very
similar to other arches.

memblocks_present() is a direct replacement of arm64_memory_present()

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
---
 arch/arm64/mm/init.c | 20 +-------------------
 1 file changed, 1 insertion(+), 19 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 6a0b5c5a61af..c51a944fe19f 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -296,24 +296,6 @@ int pfn_valid(unsigned long pfn)
 EXPORT_SYMBOL(pfn_valid);
 #endif
 
-#ifndef CONFIG_SPARSEMEM
-static void __init arm64_memory_present(void)
-{
-}
-#else
-static void __init arm64_memory_present(void)
-{
-	struct memblock_region *reg;
-
-	for_each_memblock(memory, reg) {
-		int nid = memblock_get_region_node(reg);
-
-		memory_present(nid, memblock_region_memory_base_pfn(reg),
-				memblock_region_memory_end_pfn(reg));
-	}
-}
-#endif
-
 static phys_addr_t memory_limit = PHYS_ADDR_MAX;
 
 /*
@@ -506,7 +488,7 @@ void __init bootmem_init(void)
 	 * Sparsemem tries to allocate bootmem in memory_present(), so must be
 	 * done after the fixed reservations.
 	 */
-	arm64_memory_present();
+	memblocks_present();
 
 	sparse_init();
 	zone_sizes_init(min, max);
-- 
2.19.0

[PATCH v2 5/6] sh: mm: make use of new memblocks_present() helper

[Logan Gunthorpe]

Cleanup the open coded for_each_memblock() loop that is equivalent
to the new memblocks_present() helper.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Rich Felker <dalias@libc.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Rob Herring <robh@kernel.org>
---
 arch/sh/mm/init.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/sh/mm/init.c b/arch/sh/mm/init.c
index 7713c084d040..f601f96408ee 100644
--- a/arch/sh/mm/init.c
+++ b/arch/sh/mm/init.c
@@ -235,12 +235,7 @@ static void __init do_init_bootmem(void)
 
 	plat_mem_setup();
 
-	for_each_memblock(memory, reg) {
-		int nid = memblock_get_region_node(reg);
-
-		memory_present(nid, memblock_region_memory_base_pfn(reg),
-			memblock_region_memory_end_pfn(reg));
-	}
+	memblocks_present();
 	sparse_init();
 }
 
-- 
2.19.0

[PATCH v2 6/6] RISC-V: Implement sparsemem

[Logan Gunthorpe]

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@deltatee.com>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Andrew Waterman <andrew@sifive.com>
Cc: Olof Johansson <olof@lixom.net>
Cc: Michael Clark <michaeljclark@mac.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Zong Li <zong@andestech.com>
---
 arch/riscv/Kconfig                 | 23 +++++++++++++++++++++++
 arch/riscv/include/asm/pgtable.h   | 21 +++++++++++++++++----
 arch/riscv/include/asm/sparsemem.h | 11 +++++++++++
 arch/riscv/kernel/setup.c          |  4 +++-
 arch/riscv/mm/init.c               |  8 ++++++++
 5 files changed, 62 insertions(+), 5 deletions(-)
 create mode 100644 arch/riscv/include/asm/sparsemem.h

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..e1162336f5ea 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -89,6 +89,23 @@ 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.
@@ -411,10 +428,6 @@ 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..215530b24336
--- /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 /* CONFIG_SPARSEMEM */
+
+#endif /* __ASM_SPARSEMEM_H */
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index b2d26d9d8489..494c380e4ea6 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
-- 
2.19.0

Re: [PATCH v2 6/6] RISC-V: Implement sparsemem

[Nick Kossifidis]

Hello Logan,

Στις 2018-10-15 20:57, Logan Gunthorpe έγραψε:
> 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@deltatee.com>
> Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
> Cc: Albert Ou <aou@eecs.berkeley.edu>
> Cc: Andrew Waterman <andrew@sifive.com>
> Cc: Olof Johansson <olof@lixom.net>
> Cc: Michael Clark <michaeljclark@mac.com>
> Cc: Rob Herring <robh@kernel.org>
> Cc: Zong Li <zong@andestech.com>
> ---
>  arch/riscv/Kconfig                 | 23 +++++++++++++++++++++++
>  arch/riscv/include/asm/pgtable.h   | 21 +++++++++++++++++----
>  arch/riscv/include/asm/sparsemem.h | 11 +++++++++++
>  arch/riscv/kernel/setup.c          |  4 +++-
>  arch/riscv/mm/init.c               |  8 ++++++++
>  5 files changed, 62 insertions(+), 5 deletions(-)
>  create mode 100644 arch/riscv/include/asm/sparsemem.h
> 
> 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..e1162336f5ea 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -89,6 +89,23 @@ 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.
> @@ -411,10 +428,6 @@ 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..215530b24336
> --- /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

Having memory blocks of a minimum size of 1GB doesn't make much sense. 
It makes it harder to implement hotplug on top of this since we'll only 
able to add/remove 1GB at a time. ARM used to do the same and they 
switched to 27bits (https://patchwork.kernel.org/patch/9172845/), ARM64 
still uses 1GB, x86 also uses 27bits and most archs also use something 
below 30. I believe we should go for 27bits as well or even better have 
this as a compile time option.

BTW memblocks_present is on master now (got merged 3 days ago).

Regards,
N.

Re: [PATCH v2 6/6] RISC-V: Implement sparsemem

[Logan Gunthorpe]

On 2018-12-17 7:59 a.m., Nick Kossifidis wrote:
> Having memory blocks of a minimum size of 1GB doesn't make much sense. 
> It makes it harder to implement hotplug on top of this since we'll only 
> able to add/remove 1GB at a time. ARM used to do the same and they 
> switched to 27bits (https://patchwork.kernel.org/patch/9172845/), ARM64 
> still uses 1GB, x86 also uses 27bits and most archs also use something 
> below 30. I believe we should go for 27bits as well or even better have 
> this as a compile time option.

Thanks, that makes sense. I'll make the change for the next time we submit.

> BTW memblocks_present is on master now (got merged 3 days ago).

Great! We'll send an updated patch set after the merge window.

Logan

Re: [PATCH v2 0/6] sparsemem support for RISC-V

[Palmer Dabbelt]

On Mon, 15 Oct 2018 10:56:56 PDT (-0700), logang@deltatee.com wrote:
> This patchset implements sparsemem on RISC-V. The first few patches
> move some code in existing architectures into common helpers
> so they can be used by the new RISC-V implementation. The final
> patch actually adds sparsmem support to RISC-V.
>
> This is the first small step in supporting P2P on RISC-V.

Thanks.  I see less maintainer tags for the parts that touch other ports than I 
would feel comfortable merging.  I'm going to let this sit in my inbox for 
a bit and we'll see if anything collects.

For patch sets I submit that clean up other ports I've attempted to split the 
patch into N patch sets, where:

* One part adds the generic support, which starts out as dead code.
* One part per arch uses the generic support.

This is a bit of a headache, but it at least allows us to get the RISC-V 
version that uses the generic support in quickly while waiting on acks from the 
other arch maintainers.

Like I said, I'll wait a bit and hope people ack.

Thanks!