On Mon, 6 Dec 2021 11:46:51 +0100
Alexandre Ghiti <alexandre.ghiti@xxxxxxxxxxxxx> wrote:
> 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 offers
> 128TB 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 <alexandre.ghiti@xxxxxxxxxxxxx>
> ---
> arch/riscv/Kconfig | 4 +-
> arch/riscv/include/asm/csr.h | 3 +-
> arch/riscv/include/asm/fixmap.h | 1 +
> arch/riscv/include/asm/kasan.h | 6 +-
> arch/riscv/include/asm/page.h | 14 ++
> arch/riscv/include/asm/pgalloc.h | 40 +++++
> arch/riscv/include/asm/pgtable-64.h | 108 +++++++++++-
> arch/riscv/include/asm/pgtable.h | 24 ++-
> arch/riscv/kernel/head.S | 3 +-
> arch/riscv/mm/context.c | 4 +-
> arch/riscv/mm/init.c | 212 +++++++++++++++++++++---
> arch/riscv/mm/kasan_init.c | 137 ++++++++++++++-
> drivers/firmware/efi/libstub/efi-stub.c | 2 +
> 13 files changed, 514 insertions(+), 44 deletions(-)
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index ac6c0cd9bc29..d28fe0148e13 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -150,7 +150,7 @@ config PAGE_OFFSET
> hex
> default 0xC0000000 if 32BIT
> default 0x80000000 if 64BIT && !MMU
> - default 0xffffffd800000000 if 64BIT
> + default 0xffffaf8000000000 if 64BIT
>
> config KASAN_SHADOW_OFFSET
> hex
> @@ -201,7 +201,7 @@ config FIX_EARLYCON_MEM
>
> config PGTABLE_LEVELS
> int
> - default 3 if 64BIT
> + default 4 if 64BIT
> default 2
>
> config LOCKDEP_SUPPORT
> diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
> index 87ac65696871..3fdb971c7896 100644
> --- a/arch/riscv/include/asm/csr.h
> +++ b/arch/riscv/include/asm/csr.h
> @@ -40,14 +40,13 @@
> #ifndef CONFIG_64BIT
> #define SATP_PPN _AC(0x003FFFFF, UL)
> #define SATP_MODE_32 _AC(0x80000000, UL)
> -#define SATP_MODE SATP_MODE_32
> #define SATP_ASID_BITS 9
> #define SATP_ASID_SHIFT 22
> #define SATP_ASID_MASK _AC(0x1FF, UL)
> #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)
> #define SATP_ASID_BITS 16
> #define SATP_ASID_SHIFT 44
> #define SATP_ASID_MASK _AC(0xFFFF, UL)
> diff --git a/arch/riscv/include/asm/fixmap.h b/arch/riscv/include/asm/fixmap.h
> index 54cbf07fb4e9..58a718573ad6 100644
> --- a/arch/riscv/include/asm/fixmap.h
> +++ b/arch/riscv/include/asm/fixmap.h
> @@ -24,6 +24,7 @@ enum fixed_addresses {
> FIX_HOLE,
> FIX_PTE,
> FIX_PMD,
> + FIX_PUD,
> FIX_TEXT_POKE1,
> FIX_TEXT_POKE0,
> FIX_EARLYCON_MEM_BASE,
> diff --git a/arch/riscv/include/asm/kasan.h b/arch/riscv/include/asm/kasan.h
> index 743e6ff57996..0b85e363e778 100644
> --- a/arch/riscv/include/asm/kasan.h
> +++ b/arch/riscv/include/asm/kasan.h
> @@ -28,7 +28,11 @@
> #define KASAN_SHADOW_SCALE_SHIFT 3
>
> #define KASAN_SHADOW_SIZE (UL(1) << ((VA_BITS - 1) - KASAN_SHADOW_SCALE_SHIFT))
> -#define KASAN_SHADOW_START (KASAN_SHADOW_END - KASAN_SHADOW_SIZE)
> +/*
> + * Depending on the size of the virtual address space, the region may not be
> + * aligned on PGDIR_SIZE, so force its alignment to ease its population.
> + */
> +#define KASAN_SHADOW_START ((KASAN_SHADOW_END - KASAN_SHADOW_SIZE) & PGDIR_MASK)
> #define KASAN_SHADOW_END MODULES_LOWEST_VADDR
> #define KASAN_SHADOW_OFFSET _AC(CONFIG_KASAN_SHADOW_OFFSET, UL)
>
> diff --git a/arch/riscv/include/asm/page.h b/arch/riscv/include/asm/page.h
> index e03559f9b35e..d089fe46f7d8 100644
> --- a/arch/riscv/include/asm/page.h
> +++ b/arch/riscv/include/asm/page.h
> @@ -31,7 +31,20 @@
> * When not using MMU this corresponds to the first free page in
> * physical memory (aligned on a page boundary).
> */
> +#ifdef CONFIG_64BIT
> +#ifdef CONFIG_MMU
> +#define PAGE_OFFSET kernel_map.page_offset
> +#else
> +#define PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL)
> +#endif
> +/*
> + * By default, CONFIG_PAGE_OFFSET value corresponds to SV48 address space so
> + * define the PAGE_OFFSET value for SV39.
> + */
> +#define PAGE_OFFSET_L3 _AC(0xffffffd800000000, UL)
> +#else
> #define PAGE_OFFSET _AC(CONFIG_PAGE_OFFSET, UL)
> +#endif /* CONFIG_64BIT */
>
> /*
> * Half of the kernel address space (half of the entries of the page global
> @@ -90,6 +103,7 @@ extern unsigned long riscv_pfn_base;
> #endif /* CONFIG_MMU */
>
> struct kernel_mapping {
> + unsigned long page_offset;
> unsigned long virt_addr;
> uintptr_t phys_addr;
> uintptr_t size;
> diff --git a/arch/riscv/include/asm/pgalloc.h b/arch/riscv/include/asm/pgalloc.h
> index 0af6933a7100..11823004b87a 100644
> --- a/arch/riscv/include/asm/pgalloc.h
> +++ b/arch/riscv/include/asm/pgalloc.h
> @@ -11,6 +11,8 @@
> #include <asm/tlb.h>
>
> #ifdef CONFIG_MMU
> +#define __HAVE_ARCH_PUD_ALLOC_ONE
> +#define __HAVE_ARCH_PUD_FREE
> #include <asm-generic/pgalloc.h>
>
> static inline void pmd_populate_kernel(struct mm_struct *mm,
> @@ -36,6 +38,44 @@ 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));
> + }
> +}
> +
> +#define pud_alloc_one pud_alloc_one
> +static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
> +{
> + if (pgtable_l4_enabled)
> + return __pud_alloc_one(mm, addr);
> +
> + return NULL;
> +}
> +
> +#define pud_free pud_free
> +static inline void pud_free(struct mm_struct *mm, pud_t *pud)
> +{
> + if (pgtable_l4_enabled)
> + __pud_free(mm, pud);
> +}
> +
> +#define __pud_free_tlb(tlb, pud, addr) pud_free((tlb)->mm, pud)
> #endif /* __PAGETABLE_PMD_FOLDED */
>
> static inline pgd_t *pgd_alloc(struct mm_struct *mm)
> diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
> index 228261aa9628..bbbdd66e5e2f 100644
> --- a/arch/riscv/include/asm/pgtable-64.h
> +++ b/arch/riscv/include/asm/pgtable-64.h
> @@ -8,16 +8,36 @@
>
> #include <linux/const.h>
>
> -#define PGDIR_SHIFT 30
> +extern bool pgtable_l4_enabled;
> +
> +#define PGDIR_SHIFT_L3 30
> +#define PGDIR_SHIFT_L4 39
> +#define PGDIR_SIZE_L3 (_AC(1, UL) << PGDIR_SHIFT_L3)
> +
> +#define PGDIR_SHIFT (pgtable_l4_enabled ? PGDIR_SHIFT_L4 : PGDIR_SHIFT_L3)
> /* 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;
> @@ -59,6 +79,16 @@ 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 pmd_t *pud_pgtable(pud_t pud)
> {
> return (pmd_t *)pfn_to_virt(pud_val(pud) >> _PAGE_PFN_SHIFT);
> @@ -69,6 +99,17 @@ 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 pfn_pmd(unsigned long pfn, pgprot_t prot)
> {
> return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
> @@ -84,4 +125,69 @@ 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 pud_t *p4d_pgtable(p4d_t p4d)
> +{
> + if (pgtable_l4_enabled)
> + return (pud_t *)pfn_to_virt(p4d_val(p4d) >> _PAGE_PFN_SHIFT);
> +
> + return (pud_t *)pud_pgtable((pud_t) { p4d_val(p4d) });
> +}
> +
> +static inline struct page *p4d_page(p4d_t p4d)
> +{
> + return pfn_to_page(p4d_val(p4d) >> _PAGE_PFN_SHIFT);
> +}
> +
> +#define pud_index(addr) (((addr) >> PUD_SHIFT) & (PTRS_PER_PUD - 1))
> +
> +#define pud_offset pud_offset
> +static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address)
> +{
> + if (pgtable_l4_enabled)
> + return p4d_pgtable(*p4d) + pud_index(address);
> +
> + return (pud_t *)p4d;
> +}
> +
> #endif /* _ASM_RISCV_PGTABLE_64_H */
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index e1a52e22ad7e..e1c74ef4ead2 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -51,7 +51,7 @@
> * position vmemmap directly below the VMALLOC region.
> */
> #ifdef CONFIG_64BIT
> -#define VA_BITS 39
> +#define VA_BITS (pgtable_l4_enabled ? 48 : 39)
> #else
> #define VA_BITS 32
> #endif
> @@ -90,8 +90,7 @@
>
> #ifndef __ASSEMBLY__
>
> -/* Page Upper Directory not used in RISC-V */
> -#include <asm-generic/pgtable-nopud.h>
> +#include <asm-generic/pgtable-nop4d.h>
> #include <asm/page.h>
> #include <asm/tlbflush.h>
> #include <linux/mm_types.h>
> @@ -113,6 +112,17 @@
> #define XIP_FIXUP(addr) (addr)
> #endif /* CONFIG_XIP_KERNEL */
>
> +struct pt_alloc_ops {
> + pte_t *(*get_pte_virt)(phys_addr_t pa);
> + phys_addr_t (*alloc_pte)(uintptr_t va);
> +#ifndef __PAGETABLE_PMD_FOLDED
> + pmd_t *(*get_pmd_virt)(phys_addr_t pa);
> + phys_addr_t (*alloc_pmd)(uintptr_t va);
> + pud_t *(*get_pud_virt)(phys_addr_t pa);
> + phys_addr_t (*alloc_pud)(uintptr_t va);
> +#endif
> +};
> +
> #ifdef CONFIG_MMU
> /* Number of entries in the page global directory */
> #define PTRS_PER_PGD (PAGE_SIZE / sizeof(pgd_t))
> @@ -669,9 +679,11 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
> * Note that PGDIR_SIZE must evenly divide TASK_SIZE.
> */
> #ifdef CONFIG_64BIT
> -#define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
> +#define TASK_SIZE (PGDIR_SIZE * PTRS_PER_PGD / 2)
> +#define TASK_SIZE_MIN (PGDIR_SIZE_L3 * PTRS_PER_PGD / 2)
> #else
> -#define TASK_SIZE FIXADDR_START
> +#define TASK_SIZE FIXADDR_START
> +#define TASK_SIZE_MIN TASK_SIZE
> #endif
>
> #else /* CONFIG_MMU */
> @@ -697,6 +709,8 @@ extern uintptr_t _dtb_early_pa;
> #define dtb_early_va _dtb_early_va
> #define dtb_early_pa _dtb_early_pa
> #endif /* CONFIG_XIP_KERNEL */
> +extern u64 satp_mode;
> +extern bool pgtable_l4_enabled;
>
> void paging_init(void);
> void misc_mem_init(void);
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 52c5ff9804c5..c3c0ed559770 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -95,7 +95,8 @@ relocate:
>
> /* Compute satp for kernel page tables, but don't load it yet */
> srl a2, a0, PAGE_SHIFT
> - li a1, SATP_MODE
> + la a1, satp_mode
> + REG_L a1, 0(a1)
> or a2, a2, a1
>
> /*
> diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
> index ee3459cb6750..a7246872bd30 100644
> --- a/arch/riscv/mm/context.c
> +++ b/arch/riscv/mm/context.c
> @@ -192,7 +192,7 @@ static void set_mm_asid(struct mm_struct *mm, unsigned int cpu)
> switch_mm_fast:
> csr_write(CSR_SATP, virt_to_pfn(mm->pgd) |
> ((cntx & asid_mask) << SATP_ASID_SHIFT) |
> - SATP_MODE);
> + satp_mode);
>
> if (need_flush_tlb)
> local_flush_tlb_all();
> @@ -201,7 +201,7 @@ static void set_mm_asid(struct mm_struct *mm, unsigned int cpu)
> static void set_mm_noasid(struct mm_struct *mm)
> {
> /* Switch the page table and blindly nuke entire local TLB */
> - csr_write(CSR_SATP, virt_to_pfn(mm->pgd) | SATP_MODE);
> + csr_write(CSR_SATP, virt_to_pfn(mm->pgd) | satp_mode);
> local_flush_tlb_all();
> }
>
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 1552226fb6bd..6a19a1b1caf8 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -37,6 +37,17 @@ EXPORT_SYMBOL(kernel_map);
> #define kernel_map (*(struct kernel_mapping *)XIP_FIXUP(&kernel_map))
> #endif
>
> +#ifdef CONFIG_64BIT
> +u64 satp_mode = !IS_ENABLED(CONFIG_XIP_KERNEL) ? SATP_MODE_48 : SATP_MODE_39;
> +#else
> +u64 satp_mode = SATP_MODE_32;
> +#endif
> +EXPORT_SYMBOL(satp_mode);
> +
> +bool pgtable_l4_enabled = IS_ENABLED(CONFIG_64BIT) && !IS_ENABLED(CONFIG_XIP_KERNEL) ?
> + true : false;
Hi Alex,
I'm not sure whether we can use static key for pgtable_l4_enabled or
not. Obviously, for a specific HW platform, pgtable_l4_enabled won't change
after boot, and it seems it sits hot code path, so IMHO, static key maybe
suitable for it.
Thanks
