Re: [PATCH v2 5/8] riscv: Implement sv48 support
From: Nick Kossifidis
Date: Sat Jun 27 2020 - 08:31:56 EST
ÎÏÎÏ 2020-06-03 11:11, Alexandre Ghiti ÎÎÏÎÏÎ:
By adding a new 4th level of page table, give the possibility to 64bit
kernel to address 2^48 bytes of virtual address: in practice, that
roughly
offers ~160TB of virtual address space to userspace and allows up to
64TB
of physical memory.
If the underlying hardware does not support sv48, we will automatically
fallback to a standard 3-level page table by folding the new PUD level
into
PGDIR level. In order to detect HW capabilities at runtime, we
use SATP feature that ignores writes with an unsupported mode.
Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
---
arch/riscv/Kconfig | 6 +-
arch/riscv/include/asm/csr.h | 3 +-
arch/riscv/include/asm/fixmap.h | 1 +
arch/riscv/include/asm/page.h | 15 +++
arch/riscv/include/asm/pgalloc.h | 36 +++++++
arch/riscv/include/asm/pgtable-64.h | 97 ++++++++++++++++-
arch/riscv/include/asm/pgtable.h | 10 +-
arch/riscv/kernel/head.S | 3 +-
arch/riscv/mm/context.c | 2 +-
arch/riscv/mm/init.c | 158 +++++++++++++++++++++++++---
10 files changed, 307 insertions(+), 24 deletions(-)
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index e167f16131f4..3f73f60e9732 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -68,6 +68,7 @@ config RISCV
select ARCH_HAS_GCOV_PROFILE_ALL
select HAVE_COPY_THREAD_TLS
select HAVE_ARCH_KASAN if MMU && 64BIT
+ select RELOCATABLE if 64BIT
config ARCH_MMAP_RND_BITS_MIN
default 18 if 64BIT
@@ -106,7 +107,7 @@ config PAGE_OFFSET
default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
default 0x80000000 if 64BIT && !MMU
default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
- default 0xffffffe000000000 if 64BIT && !MAXPHYSMEM_2GB
+ default 0xffffc00000000000 if 64BIT && !MAXPHYSMEM_2GB
config ARCH_FLATMEM_ENABLE
def_bool y
@@ -155,8 +156,11 @@ config GENERIC_HWEIGHT
config FIX_EARLYCON_MEM
def_bool MMU
+# On a 64BIT relocatable kernel, the 4-level page table is at runtime
folded
+# on a 3-level page table when sv48 is not supported.
config PGTABLE_LEVELS
int
+ default 4 if 64BIT && RELOCATABLE
default 3 if 64BIT
default 2
diff --git a/arch/riscv/include/asm/csr.h
b/arch/riscv/include/asm/csr.h
index cec462e198ce..d41536c3f8d4 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -40,11 +40,10 @@
#ifndef CONFIG_64BIT
#define SATP_PPN _AC(0x003FFFFF, UL)
#define SATP_MODE_32 _AC(0x80000000, UL)
-#define SATP_MODE SATP_MODE_32
#else
#define SATP_PPN _AC(0x00000FFFFFFFFFFF, UL)
#define SATP_MODE_39 _AC(0x8000000000000000, UL)
-#define SATP_MODE SATP_MODE_39
+#define SATP_MODE_48 _AC(0x9000000000000000, UL)
#endif
/* Exception cause high bit - is an interrupt if set */
diff --git a/arch/riscv/include/asm/fixmap.h
b/arch/riscv/include/asm/fixmap.h
index 2368d49eb4ef..d891cf9c73c5 100644
--- a/arch/riscv/include/asm/fixmap.h
+++ b/arch/riscv/include/asm/fixmap.h
@@ -27,6 +27,7 @@ enum fixed_addresses {
FIX_FDT = FIX_FDT_END + FIX_FDT_SIZE / PAGE_SIZE - 1,
FIX_PTE,
FIX_PMD,
+ FIX_PUD,
FIX_TEXT_POKE1,
FIX_TEXT_POKE0,
FIX_EARLYCON_MEM_BASE,
diff --git a/arch/riscv/include/asm/page.h
b/arch/riscv/include/asm/page.h
index 48bb09b6a9b7..5e77fe7f0d6d 100644
--- a/arch/riscv/include/asm/page.h
+++ b/arch/riscv/include/asm/page.h
@@ -31,7 +31,19 @@
* When not using MMU this corresponds to the first free page in
* physical memory (aligned on a page boundary).
*/
+#ifdef CONFIG_RELOCATABLE
+#define PAGE_OFFSET __page_offset
+
+#ifdef CONFIG_64BIT
+/*
+ * By default, CONFIG_PAGE_OFFSET value corresponds to SV48 address
space so
+ * define the PAGE_OFFSET value for SV39.
+ */
+#define PAGE_OFFSET_L3 0xffffffe000000000
+#endif /* CONFIG_64BIT */
+#else
#define PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL)
+#endif /* CONFIG_RELOCATABLE */
#define KERN_VIRT_SIZE (-PAGE_OFFSET)
@@ -102,6 +114,9 @@ extern unsigned long pfn_base;
extern unsigned long max_low_pfn;
extern unsigned long min_low_pfn;
extern unsigned long kernel_virt_addr;
+#ifdef CONFIG_RELOCATABLE
+extern unsigned long __page_offset;
+#endif
#define __pa_to_va_nodebug(x) ((void *)((unsigned long) (x) +
va_pa_offset))
#define linear_mapping_va_to_pa(x) ((unsigned long)(x) - va_pa_offset)
diff --git a/arch/riscv/include/asm/pgalloc.h
b/arch/riscv/include/asm/pgalloc.h
index 3f601ee8233f..540eaa5a8658 100644
--- a/arch/riscv/include/asm/pgalloc.h
+++ b/arch/riscv/include/asm/pgalloc.h
@@ -36,6 +36,42 @@ static inline void pud_populate(struct mm_struct
*mm, pud_t *pud, pmd_t *pmd)
set_pud(pud, __pud((pfn << _PAGE_PFN_SHIFT) | _PAGE_TABLE));
}
+
+static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4d,
pud_t *pud)
+{
+ if (pgtable_l4_enabled) {
+ unsigned long pfn = virt_to_pfn(pud);
+
+ set_p4d(p4d, __p4d((pfn << _PAGE_PFN_SHIFT) | _PAGE_TABLE));
+ }
+}
+
+static inline void p4d_populate_safe(struct mm_struct *mm, p4d_t *p4d,
+ pud_t *pud)
+{
+ if (pgtable_l4_enabled) {
+ unsigned long pfn = virt_to_pfn(pud);
+
+ set_p4d_safe(p4d,
+ __p4d((pfn << _PAGE_PFN_SHIFT) | _PAGE_TABLE));
+ }
+}
+
+static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long
addr)
+{
+ if (pgtable_l4_enabled)
+ return (pud_t *)__get_free_page(
+ GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_ZERO);
+ return NULL;
+}
+
+static inline void pud_free(struct mm_struct *mm, pud_t *pud)
+{
+ if (pgtable_l4_enabled)
+ free_page((unsigned long)pud);
+}
+
+#define __pud_free_tlb(tlb, pud, addr) pud_free((tlb)->mm, pud)
#endif /* __PAGETABLE_PMD_FOLDED */
#define pmd_pgtable(pmd) pmd_page(pmd)
diff --git a/arch/riscv/include/asm/pgtable-64.h
b/arch/riscv/include/asm/pgtable-64.h
index b15f70a1fdfa..c84c31fbf8da 100644
--- a/arch/riscv/include/asm/pgtable-64.h
+++ b/arch/riscv/include/asm/pgtable-64.h
@@ -8,16 +8,32 @@
#include <linux/const.h>
-#define PGDIR_SHIFT 30
+extern bool pgtable_l4_enabled;
+
+#define PGDIR_SHIFT (pgtable_l4_enabled ? 39 : 30)
/* Size of region mapped by a page global directory */
#define PGDIR_SIZE (_AC(1, UL) << PGDIR_SHIFT)
#define PGDIR_MASK (~(PGDIR_SIZE - 1))
+/* pud is folded into pgd in case of 3-level page table */
+#define PUD_SHIFT 30
+#define PUD_SIZE (_AC(1, UL) << PUD_SHIFT)
+#define PUD_MASK (~(PUD_SIZE - 1))
+
#define PMD_SHIFT 21
/* Size of region mapped by a page middle directory */
#define PMD_SIZE (_AC(1, UL) << PMD_SHIFT)
#define PMD_MASK (~(PMD_SIZE - 1))
+/* Page Upper Directory entry */
+typedef struct {
+ unsigned long pud;
+} pud_t;
+
+#define pud_val(x) ((x).pud)
+#define __pud(x) ((pud_t) { (x) })
+#define PTRS_PER_PUD (PAGE_SIZE / sizeof(pud_t))
+
/* Page Middle Directory entry */
typedef struct {
unsigned long pmd;
@@ -60,6 +76,16 @@ static inline void pud_clear(pud_t *pudp)
set_pud(pudp, __pud(0));
}
+static inline pud_t pfn_pud(unsigned long pfn, pgprot_t prot)
+{
+ return __pud((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
+}
+
+static inline unsigned long _pud_pfn(pud_t pud)
+{
+ return pud_val(pud) >> _PAGE_PFN_SHIFT;
+}
+
static inline unsigned long pud_page_vaddr(pud_t pud)
{
return (unsigned long)pfn_to_virt(pud_val(pud) >> _PAGE_PFN_SHIFT);
@@ -70,6 +96,15 @@ static inline struct page *pud_page(pud_t pud)
return pfn_to_page(pud_val(pud) >> _PAGE_PFN_SHIFT);
}
+#define mm_pud_folded mm_pud_folded
+static inline bool mm_pud_folded(struct mm_struct *mm)
+{
+ if (pgtable_l4_enabled)
+ return false;
+
+ return true;
+}
+
#define pmd_index(addr) (((addr) >> PMD_SHIFT) & (PTRS_PER_PMD - 1))
static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
@@ -90,4 +125,64 @@ static inline unsigned long _pmd_pfn(pmd_t pmd)
#define pmd_ERROR(e) \
pr_err("%s:%d: bad pmd %016lx.\n", __FILE__, __LINE__, pmd_val(e))
+#define pud_ERROR(e) \
+ pr_err("%s:%d: bad pud %016lx.\n", __FILE__, __LINE__, pud_val(e))
+
+static inline void set_p4d(p4d_t *p4dp, p4d_t p4d)
+{
+ if (pgtable_l4_enabled)
+ *p4dp = p4d;
+ else
+ set_pud((pud_t *)p4dp, (pud_t){ p4d_val(p4d) });
+}
+
+static inline int p4d_none(p4d_t p4d)
+{
+ if (pgtable_l4_enabled)
+ return (p4d_val(p4d) == 0);
+
+ return 0;
+}
+
+static inline int p4d_present(p4d_t p4d)
+{
+ if (pgtable_l4_enabled)
+ return (p4d_val(p4d) & _PAGE_PRESENT);
+
+ return 1;
+}
+
+static inline int p4d_bad(p4d_t p4d)
+{
+ if (pgtable_l4_enabled)
+ return !p4d_present(p4d);
+
+ return 0;
+}
+
+static inline void p4d_clear(p4d_t *p4d)
+{
+ if (pgtable_l4_enabled)
+ set_p4d(p4d, __p4d(0));
+}
+
+static inline unsigned long p4d_page_vaddr(p4d_t p4d)
+{
+ if (pgtable_l4_enabled)
+ return (unsigned long)pfn_to_virt(
+ p4d_val(p4d) >> _PAGE_PFN_SHIFT);
+
+ return pud_page_vaddr((pud_t) { p4d_val(p4d) });
+}
+
+#define pud_index(addr) (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
+
+static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)
+{
+ if (pgtable_l4_enabled)
+ return (pud_t *)p4d_page_vaddr(*p4d) + pud_index(address);
+
+ return (pud_t *)p4d;
+}
+
In my test I had to put
#define pud_offset pud_offset
here or else I got a compilation error due to pud_offset being redefined
on include/linux/pgtable.h:
#ifndef pud_offset
static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)
{
return (pud_t *)p4d_page_vaddr(*p4d) + pud_index(address);
}
#define pud_offset pud_offset
#endif