[PATCH 1/3] riscv: Introduce huge page support for 32/64bit kernel

[Alexandre Ghiti <aghiti@upmem.com>]

This patch implements both 4MB huge page support for 32bit kernel
and 2MB/1GB huge pages support for 64bit kernel.

Signed-off-by: Alexandre Ghiti <aghiti@upmem.com>
---
 arch/riscv/Kconfig               |  7 +++++++
 arch/riscv/include/asm/hugetlb.h | 22 ++++++++++++++++++++++
 arch/riscv/include/asm/page.h    | 10 ++++++++++
 arch/riscv/include/asm/pgtable.h |  6 +++++-
 arch/riscv/mm/Makefile           |  2 ++
 arch/riscv/mm/hugetlbpage.c      | 36 ++++++++++++++++++++++++++++++++++++
 6 files changed, 82 insertions(+), 1 deletion(-)
 create mode 100644 arch/riscv/include/asm/hugetlb.h
 create mode 100644 arch/riscv/mm/hugetlbpage.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 55da93f4e818..7bb21533d927 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -57,6 +57,12 @@ config PAGE_OFFSET
 	default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
 	default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
 
+config ARCH_WANT_GENERAL_HUGETLB
+	def_bool y
+
+config SYS_SUPPORTS_HUGETLBFS
+	def_bool y
+
 config STACKTRACE_SUPPORT
 	def_bool y
 
@@ -118,6 +124,7 @@ config ARCH_RV64I
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_DYNAMIC_FTRACE_WITH_REGS
 	select SWIOTLB
+	select ARCH_HAS_GIGANTIC_PAGE if (MEMORY_ISOLATION && COMPACTION) || CMA
 
 endchoice
 
diff --git a/arch/riscv/include/asm/hugetlb.h b/arch/riscv/include/asm/hugetlb.h
new file mode 100644
index 000000000000..b7d88cf4e315
--- /dev/null
+++ b/arch/riscv/include/asm/hugetlb.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_RISCV_HUGETLB_H
+#define _ASM_RISCV_HUGETLB_H
+
+#include <asm-generic/hugetlb.h>
+#include <asm/page.h>
+
+static inline int is_hugepage_only_range(struct mm_struct *mm,
+					 unsigned long addr,
+					 unsigned long len) {
+	return 0;
+}
+
+static inline void arch_clear_hugepage_flags(struct page *page)
+{
+}
+
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
+static inline bool gigantic_page_supported(void) { return true; }
+#endif
+
+#endif /* _ASM_RISCV_HUGETLB_H */
diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
index 06cfbb3aacbb..ceaa73b82b25 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -24,6 +24,16 @@
 #define PAGE_SIZE	(_AC(1, UL) << PAGE_SHIFT)
 #define PAGE_MASK	(~(PAGE_SIZE - 1))
 
+#ifdef CONFIG_64BIT
+#define HUGE_MAX_HSTATE		2
+#else
+#define HUGE_MAX_HSTATE		1
+#endif
+#define HPAGE_SHIFT		PMD_SHIFT
+#define HPAGE_SIZE		(_AC(1, UL) << HPAGE_SHIFT)
+#define HPAGE_MASK              (~(HPAGE_SIZE - 1))
+#define HUGETLB_PAGE_ORDER      (HPAGE_SHIFT - PAGE_SHIFT)
+
 /*
  * PAGE_OFFSET -- the first address of the first page of memory.
  * When not using MMU this corresponds to the first free page in
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 16301966d65b..50ea3d6e7de7 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -121,7 +121,6 @@ static inline void pmd_clear(pmd_t *pmdp)
 	set_pmd(pmdp, __pmd(0));
 }
 
-
 static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot)
 {
 	return __pgd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
@@ -258,6 +257,11 @@ static inline pte_t pte_mkspecial(pte_t pte)
 	return __pte(pte_val(pte) | _PAGE_SPECIAL);
 }
 
+static inline pte_t pte_mkhuge(pte_t pte)
+{
+	return pte;
+}
+
 /* Modify page protection bits */
 static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 {
diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
index eb22ab49b3e0..eeadb130d7cf 100644
--- a/arch/riscv/mm/Makefile
+++ b/arch/riscv/mm/Makefile
@@ -3,3 +3,5 @@ obj-y += fault.o
 obj-y += extable.o
 obj-y += ioremap.o
 obj-y += cacheflush.o
+
+obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o
diff --git a/arch/riscv/mm/hugetlbpage.c b/arch/riscv/mm/hugetlbpage.c
new file mode 100644
index 000000000000..7bac8b22d486
--- /dev/null
+++ b/arch/riscv/mm/hugetlbpage.c
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/hugetlb.h>
+#include <linux/err.h>
+
+int pud_huge(pud_t pud)
+{
+	return pud_present(pud)
+		&& (pud_val(pud) & (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC));
+}
+
+int pmd_huge(pmd_t pmd)
+{
+	return pmd_present(pmd)
+		&& (pmd_val(pmd) & (_PAGE_READ | _PAGE_WRITE | _PAGE_EXEC));
+}
+
+static __init int setup_hugepagesz(char *opt)
+{
+	unsigned long ps = memparse(opt, &opt);
+
+	if (ps == HPAGE_SIZE) {
+		hugetlb_add_hstate(HPAGE_SHIFT - PAGE_SHIFT);
+#if defined(CONFIG_64BIT)
+	} else if (ps == PUD_SIZE) {
+		hugetlb_add_hstate(PUD_SHIFT - PAGE_SHIFT);
+#endif
+	} else {
+		hugetlb_bad_size();
+		printk(KERN_ERR "hugepagesz: Unsupported page size %lu M\n",
+			ps >> 20);
+		return 0;
+	}
+
+	return 1;
+}
+__setup("hugepagesz=", setup_hugepagesz);
-- 
2.16.2


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