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SubjectRe: [PATCH v2 07/13] powerpc: add support for folded p4d page tables
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Le 16/02/2020 à 09:18, Mike Rapoport a écrit :
> From: Mike Rapoport <rppt@linux.ibm.com>
>
> Implement primitives necessary for the 4th level folding, add walks of p4d
> level where appropriate and replace 5level-fixup.h with pgtable-nop4d.h.

I don't think it is worth adding all this additionnals walks of p4d,
this patch could be limited to changes like:

- pud = pud_offset(pgd, gpa);
+ pud = pud_offset(p4d_offset(pgd, gpa), gpa);

The additionnal walks should be added through another patch the day
powerpc need them.

See below for more comments.

>
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> Tested-by: Christophe Leroy <christophe.leroy@c-s.fr> # 8xx and 83xx
> ---
> arch/powerpc/include/asm/book3s/32/pgtable.h | 1 -
> arch/powerpc/include/asm/book3s/64/hash.h | 4 +-
> arch/powerpc/include/asm/book3s/64/pgalloc.h | 4 +-
> arch/powerpc/include/asm/book3s/64/pgtable.h | 58 ++++++++++--------
> arch/powerpc/include/asm/book3s/64/radix.h | 6 +-
> arch/powerpc/include/asm/nohash/32/pgtable.h | 1 -
> arch/powerpc/include/asm/nohash/64/pgalloc.h | 2 +-
> .../include/asm/nohash/64/pgtable-4k.h | 32 +++++-----
> arch/powerpc/include/asm/nohash/64/pgtable.h | 6 +-
> arch/powerpc/include/asm/pgtable.h | 8 +++
> arch/powerpc/kvm/book3s_64_mmu_radix.c | 59 ++++++++++++++++---
> arch/powerpc/lib/code-patching.c | 7 ++-
> arch/powerpc/mm/book3s32/mmu.c | 2 +-
> arch/powerpc/mm/book3s32/tlb.c | 4 +-
> arch/powerpc/mm/book3s64/hash_pgtable.c | 4 +-
> arch/powerpc/mm/book3s64/radix_pgtable.c | 19 ++++--
> arch/powerpc/mm/book3s64/subpage_prot.c | 6 +-
> arch/powerpc/mm/hugetlbpage.c | 28 +++++----
> arch/powerpc/mm/kasan/kasan_init_32.c | 8 +--
> arch/powerpc/mm/mem.c | 4 +-
> arch/powerpc/mm/nohash/40x.c | 4 +-
> arch/powerpc/mm/nohash/book3e_pgtable.c | 15 +++--
> arch/powerpc/mm/pgtable.c | 25 +++++++-
> arch/powerpc/mm/pgtable_32.c | 28 +++++----
> arch/powerpc/mm/pgtable_64.c | 10 ++--
> arch/powerpc/mm/ptdump/hashpagetable.c | 20 ++++++-
> arch/powerpc/mm/ptdump/ptdump.c | 22 ++++++-
> arch/powerpc/xmon/xmon.c | 17 +++++-
> 28 files changed, 284 insertions(+), 120 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
> index 5b39c11e884a..39ec11371be0 100644
> --- a/arch/powerpc/include/asm/book3s/32/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
> @@ -2,7 +2,6 @@
> #ifndef _ASM_POWERPC_BOOK3S_32_PGTABLE_H
> #define _ASM_POWERPC_BOOK3S_32_PGTABLE_H
>
> -#define __ARCH_USE_5LEVEL_HACK
> #include <asm-generic/pgtable-nopmd.h>
>
> #include <asm/book3s/32/hash.h>
> diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
> index 2781ebf6add4..876d1528c2cf 100644
> --- a/arch/powerpc/include/asm/book3s/64/hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/hash.h
> @@ -134,9 +134,9 @@ static inline int get_region_id(unsigned long ea)
>
> #define hash__pmd_bad(pmd) (pmd_val(pmd) & H_PMD_BAD_BITS)
> #define hash__pud_bad(pud) (pud_val(pud) & H_PUD_BAD_BITS)
> -static inline int hash__pgd_bad(pgd_t pgd)
> +static inline int hash__p4d_bad(p4d_t p4d)
> {
> - return (pgd_val(pgd) == 0);
> + return (p4d_val(p4d) == 0);
> }
> #ifdef CONFIG_STRICT_KERNEL_RWX
> extern void hash__mark_rodata_ro(void);
> diff --git a/arch/powerpc/include/asm/book3s/64/pgalloc.h b/arch/powerpc/include/asm/book3s/64/pgalloc.h
> index a41e91bd0580..69c5b051734f 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgalloc.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgalloc.h
> @@ -85,9 +85,9 @@ static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
> kmem_cache_free(PGT_CACHE(PGD_INDEX_SIZE), pgd);
> }
>
> -static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud)
> +static inline void p4d_populate(struct mm_struct *mm, p4d_t *pgd, pud_t *pud)
> {
> - *pgd = __pgd(__pgtable_ptr_val(pud) | PGD_VAL_BITS);
> + *pgd = __p4d(__pgtable_ptr_val(pud) | PGD_VAL_BITS);
> }
>
> static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index 201a69e6a355..ddddbafff0ab 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -2,7 +2,7 @@
> #ifndef _ASM_POWERPC_BOOK3S_64_PGTABLE_H_
> #define _ASM_POWERPC_BOOK3S_64_PGTABLE_H_
>
> -#include <asm-generic/5level-fixup.h>
> +#include <asm-generic/pgtable-nop4d.h>
>
> #ifndef __ASSEMBLY__
> #include <linux/mmdebug.h>
> @@ -251,7 +251,7 @@ extern unsigned long __pmd_frag_size_shift;
> /* Bits to mask out from a PUD to get to the PMD page */
> #define PUD_MASKED_BITS 0xc0000000000000ffUL
> /* Bits to mask out from a PGD to get to the PUD page */
> -#define PGD_MASKED_BITS 0xc0000000000000ffUL
> +#define P4D_MASKED_BITS 0xc0000000000000ffUL
>
> /*
> * Used as an indicator for rcu callback functions
> @@ -949,54 +949,60 @@ static inline bool pud_access_permitted(pud_t pud, bool write)
> return pte_access_permitted(pud_pte(pud), write);
> }
>
> -#define pgd_write(pgd) pte_write(pgd_pte(pgd))
> +#define __p4d_raw(x) ((p4d_t) { __pgd_raw(x) })
> +static inline __be64 p4d_raw(p4d_t x)
> +{
> + return pgd_raw(x.pgd);
> +}
> +

Shouldn't this be defined in asm/pgtable-be-types.h, just like other
__pxx_raw() ?

> +#define p4d_write(p4d) pte_write(p4d_pte(p4d))
>
> -static inline void pgd_clear(pgd_t *pgdp)
> +static inline void p4d_clear(p4d_t *p4dp)
> {
> - *pgdp = __pgd(0);
> + *p4dp = __p4d(0);
> }
>
> -static inline int pgd_none(pgd_t pgd)
> +static inline int p4d_none(p4d_t p4d)
> {
> - return !pgd_raw(pgd);
> + return !p4d_raw(p4d);
> }
>
> -static inline int pgd_present(pgd_t pgd)
> +static inline int p4d_present(p4d_t p4d)
> {
> - return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT));
> + return !!(p4d_raw(p4d) & cpu_to_be64(_PAGE_PRESENT));
> }
>
> -static inline pte_t pgd_pte(pgd_t pgd)
> +static inline pte_t p4d_pte(p4d_t p4d)
> {
> - return __pte_raw(pgd_raw(pgd));
> + return __pte_raw(p4d_raw(p4d));
> }
>
> -static inline pgd_t pte_pgd(pte_t pte)
> +static inline p4d_t pte_p4d(pte_t pte)
> {
> - return __pgd_raw(pte_raw(pte));
> + return __p4d_raw(pte_raw(pte));
> }
>
> -static inline int pgd_bad(pgd_t pgd)
> +static inline int p4d_bad(p4d_t p4d)
> {
> if (radix_enabled())
> - return radix__pgd_bad(pgd);
> - return hash__pgd_bad(pgd);
> + return radix__p4d_bad(p4d);
> + return hash__p4d_bad(p4d);
> }
>
> -#define pgd_access_permitted pgd_access_permitted
> -static inline bool pgd_access_permitted(pgd_t pgd, bool write)
> +#define p4d_access_permitted p4d_access_permitted
> +static inline bool p4d_access_permitted(p4d_t p4d, bool write)
> {
> - return pte_access_permitted(pgd_pte(pgd), write);
> + return pte_access_permitted(p4d_pte(p4d), write);
> }
>
> -extern struct page *pgd_page(pgd_t pgd);
> +extern struct page *p4d_page(p4d_t p4d);
>
> /* Pointers in the page table tree are physical addresses */
> #define __pgtable_ptr_val(ptr) __pa(ptr)
>
> #define pmd_page_vaddr(pmd) __va(pmd_val(pmd) & ~PMD_MASKED_BITS)
> #define pud_page_vaddr(pud) __va(pud_val(pud) & ~PUD_MASKED_BITS)
> -#define pgd_page_vaddr(pgd) __va(pgd_val(pgd) & ~PGD_MASKED_BITS)
> +#define p4d_page_vaddr(p4d) __va(p4d_val(p4d) & ~P4D_MASKED_BITS)
>
> #define pgd_index(address) (((address) >> (PGDIR_SHIFT)) & (PTRS_PER_PGD - 1))
> #define pud_index(address) (((address) >> (PUD_SHIFT)) & (PTRS_PER_PUD - 1))
> @@ -1010,8 +1016,8 @@ extern struct page *pgd_page(pgd_t pgd);
>
> #define pgd_offset(mm, address) ((mm)->pgd + pgd_index(address))
>
> -#define pud_offset(pgdp, addr) \
> - (((pud_t *) pgd_page_vaddr(*(pgdp))) + pud_index(addr))
> +#define pud_offset(p4dp, addr) \
> + (((pud_t *) p4d_page_vaddr(*(p4dp))) + pud_index(addr))
> #define pmd_offset(pudp,addr) \
> (((pmd_t *) pud_page_vaddr(*(pudp))) + pmd_index(addr))
> #define pte_offset_kernel(dir,addr) \
> @@ -1368,6 +1374,12 @@ static inline bool pud_is_leaf(pud_t pud)
> return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
> }
>
> +#define p4d_is_leaf p4d_is_leaf
> +static inline bool p4d_is_leaf(p4d_t p4d)
> +{
> + return !!(p4d_raw(p4d) & cpu_to_be64(_PAGE_PTE));
> +}
> +
> #define pgd_is_leaf pgd_is_leaf
> #define pgd_leaf pgd_is_leaf
> static inline bool pgd_is_leaf(pgd_t pgd)

[...]

> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
> index 8cc543ed114c..0a05fddd7881 100644
> --- a/arch/powerpc/include/asm/pgtable.h
> +++ b/arch/powerpc/include/asm/pgtable.h
> @@ -139,6 +139,14 @@ static inline bool pud_is_leaf(pud_t pud)
> }
> #endif
>
> +#ifndef p4d_is_leaf
> +#define p4d_is_leaf p4d_is_leaf
> +static inline bool p4d_is_leaf(p4d_t p4d)
> +{
> + return false;
> +}
> +#endif
> +
> #ifndef pgd_is_leaf
> #define pgd_is_leaf pgd_is_leaf
> static inline bool pgd_is_leaf(pgd_t pgd)
> diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> index 803940d79b73..5aacfa0b27ef 100644
> --- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
> +++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
> @@ -494,17 +494,39 @@ static void kvmppc_unmap_free_pud(struct kvm *kvm, pud_t *pud,
> pud_free(kvm->mm, pud);
> }
>
> +static void kvmppc_unmap_free_p4d(struct kvm *kvm, p4d_t *p4d,
> + unsigned int lpid)
> +{
> + unsigned long iu;
> + p4d_t *p = p4d;
> +
> + for (iu = 0; iu < PTRS_PER_P4D; ++iu, ++p) {
> + if (!p4d_present(*p))
> + continue;
> + if (p4d_is_leaf(*p)) {
> + p4d_clear(p);
> + } else {
> + pud_t *pud;
> +
> + pud = pud_offset(p, 0);
> + kvmppc_unmap_free_pud(kvm, pud, lpid);
> + p4d_clear(p);
> + }
> + }
> + p4d_free(kvm->mm, p4d);
> +}
> +
> void kvmppc_free_pgtable_radix(struct kvm *kvm, pgd_t *pgd, unsigned int lpid)
> {
> unsigned long ig;
>
> for (ig = 0; ig < PTRS_PER_PGD; ++ig, ++pgd) {
> - pud_t *pud;
> + p4d_t *p4d;
>
> if (!pgd_present(*pgd))
> continue;
> - pud = pud_offset(pgd, 0);
> - kvmppc_unmap_free_pud(kvm, pud, lpid);
> + p4d = p4d_offset(pgd, 0);
> + kvmppc_unmap_free_p4d(kvm, p4d, lpid);
> pgd_clear(pgd);
> }
> }
> @@ -566,6 +588,7 @@ int kvmppc_create_pte(struct kvm *kvm, pgd_t *pgtable, pte_t pte,
> unsigned long *rmapp, struct rmap_nested **n_rmap)
> {
> pgd_t *pgd;
> + p4d_t *p4d, *new_p4d = NULL;
> pud_t *pud, *new_pud = NULL;
> pmd_t *pmd, *new_pmd = NULL;
> pte_t *ptep, *new_ptep = NULL;
> @@ -573,9 +596,15 @@ int kvmppc_create_pte(struct kvm *kvm, pgd_t *pgtable, pte_t pte,
>
> /* Traverse the guest's 2nd-level tree, allocate new levels needed */
> pgd = pgtable + pgd_index(gpa);
> - pud = NULL;
> + p4d = NULL;
> if (pgd_present(*pgd))
> - pud = pud_offset(pgd, gpa);
> + p4d = p4d_offset(pgd, gpa);
> + else
> + new_p4d = p4d_alloc_one(kvm->mm, gpa);
> +
> + pud = NULL;
> + if (p4d_present(*p4d))
> + pud = pud_offset(p4d, gpa);

Is it worth adding all this new code ?

My understanding is that the series objective is to get rid of
__ARCH_HAS_5LEVEL_HACK, to to add support for 5 levels to an
architecture that not need it (at least for now).
If we want to add support for 5 levels, it can be done later in another
patch.

Here I think your change could be limited to:

- pud = pud_offset(pgd, gpa);
+ pud = pud_offset(p4d_offset(pgd, gpa), gpa);


> else
> new_pud = pud_alloc_one(kvm->mm, gpa);
>
> @@ -597,12 +626,18 @@ int kvmppc_create_pte(struct kvm *kvm, pgd_t *pgtable, pte_t pte,
> /* Now traverse again under the lock and change the tree */
> ret = -ENOMEM;
> if (pgd_none(*pgd)) {
> + if (!new_p4d)
> + goto out_unlock;
> + pgd_populate(kvm->mm, pgd, new_p4d);
> + new_p4d = NULL;
> + }
> + if (p4d_none(*p4d)) {
> if (!new_pud)
> goto out_unlock;
> - pgd_populate(kvm->mm, pgd, new_pud);
> + p4d_populate(kvm->mm, p4d, new_pud);
> new_pud = NULL;
> }
> - pud = pud_offset(pgd, gpa);
> + pud = pud_offset(p4d, gpa);
> if (pud_is_leaf(*pud)) {
> unsigned long hgpa = gpa & PUD_MASK;
>
> @@ -1220,6 +1255,7 @@ static ssize_t debugfs_radix_read(struct file *file, char __user *buf,
> pgd_t *pgt;
> struct kvm_nested_guest *nested;
> pgd_t pgd, *pgdp;
> + p4d_t p4d, *p4dp;
> pud_t pud, *pudp;
> pmd_t pmd, *pmdp;
> pte_t *ptep;
> @@ -1298,7 +1334,14 @@ static ssize_t debugfs_radix_read(struct file *file, char __user *buf,
> continue;
> }
>
> - pudp = pud_offset(&pgd, gpa);
> + p4dp = p4d_offset(&pgd, gpa);
> + p4d = READ_ONCE(*p4dp);
> + if (!(p4d_val(p4d) & _PAGE_PRESENT)) {
> + gpa = (gpa & P4D_MASK) + P4D_SIZE;
> + continue;
> + }
> +
> + pudp = pud_offset(&p4d, gpa);

Same, here you are forcing a useless read with READ_ONCE().

Your change could be limited to

- pudp = pud_offset(&pgd, gpa);
+ pudp = pud_offset(p4d_offset(&pgd, gpa), gpa);

This comment applies to many other places.


> pud = READ_ONCE(*pudp);
> if (!(pud_val(pud) & _PAGE_PRESENT)) {
> gpa = (gpa & PUD_MASK) + PUD_SIZE;
> diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
> index 3345f039a876..7a59f6863cec 100644
> --- a/arch/powerpc/lib/code-patching.c
> +++ b/arch/powerpc/lib/code-patching.c
> @@ -107,13 +107,18 @@ static inline int unmap_patch_area(unsigned long addr)
> pte_t *ptep;
> pmd_t *pmdp;
> pud_t *pudp;
> + p4d_t *p4dp;
> pgd_t *pgdp;
>
> pgdp = pgd_offset_k(addr);
> if (unlikely(!pgdp))
> return -EINVAL;
>
> - pudp = pud_offset(pgdp, addr);
> + p4dp = p4d_offset(pgdp, addr);
> + if (unlikely(!p4dp))
> + return -EINVAL;
> +
> + pudp = pud_offset(p4dp, addr);
> if (unlikely(!pudp))
> return -EINVAL;
>
> diff --git a/arch/powerpc/mm/book3s32/mmu.c b/arch/powerpc/mm/book3s32/mmu.c
> index 0a1c65a2c565..b2fc3e71165c 100644
> --- a/arch/powerpc/mm/book3s32/mmu.c
> +++ b/arch/powerpc/mm/book3s32/mmu.c
> @@ -312,7 +312,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea)
>
> if (!Hash)
> return;
> - pmd = pmd_offset(pud_offset(pgd_offset(mm, ea), ea), ea);
> + pmd = pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, ea), ea), ea), ea);

If we continue like this, in ten years this like is going to be many
kilometers long.

I think the above would be worth a generic helper.

> if (!pmd_none(*pmd))
> add_hash_page(mm->context.id, ea, pmd_val(*pmd));
> }
> diff --git a/arch/powerpc/mm/book3s32/tlb.c b/arch/powerpc/mm/book3s32/tlb.c
> index 2fcd321040ff..175bc33b41b7 100644
> --- a/arch/powerpc/mm/book3s32/tlb.c
> +++ b/arch/powerpc/mm/book3s32/tlb.c
> @@ -87,7 +87,7 @@ static void flush_range(struct mm_struct *mm, unsigned long start,
> if (start >= end)
> return;
> end = (end - 1) | ~PAGE_MASK;
> - pmd = pmd_offset(pud_offset(pgd_offset(mm, start), start), start);
> + pmd = pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, start), start), start), start);
> for (;;) {
> pmd_end = ((start + PGDIR_SIZE) & PGDIR_MASK) - 1;
> if (pmd_end > end)
> @@ -145,7 +145,7 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr)
> return;
> }
> mm = (vmaddr < TASK_SIZE)? vma->vm_mm: &init_mm;
> - pmd = pmd_offset(pud_offset(pgd_offset(mm, vmaddr), vmaddr), vmaddr);
> + pmd = pmd_offset(pud_offset(p4d_offset(pgd_offset(mm, vmaddr), vmaddr), vmaddr), vmaddr);
> if (!pmd_none(*pmd))
> flush_hash_pages(mm->context.id, vmaddr, pmd_val(*pmd), 1);
> }
> diff --git a/arch/powerpc/mm/book3s64/hash_pgtable.c b/arch/powerpc/mm/book3s64/hash_pgtable.c
> index 64733b9cb20a..9cd15937e88a 100644
> --- a/arch/powerpc/mm/book3s64/hash_pgtable.c
> +++ b/arch/powerpc/mm/book3s64/hash_pgtable.c
> @@ -148,6 +148,7 @@ void hash__vmemmap_remove_mapping(unsigned long start,
> int hash__map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot)
> {
> pgd_t *pgdp;
> + p4d_t *p4dp;
> pud_t *pudp;
> pmd_t *pmdp;
> pte_t *ptep;
> @@ -155,7 +156,8 @@ int hash__map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot)
> BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE);
> if (slab_is_available()) {
> pgdp = pgd_offset_k(ea);
> - pudp = pud_alloc(&init_mm, pgdp, ea);
> + p4dp = p4d_offset(pgdp, ea);
> + pudp = pud_alloc(&init_mm, p4dp, ea);

Could be a single line, without a new var.

- pudp = pud_alloc(&init_mm, pgdp, ea);
+ pudp = pud_alloc(&init_mm, p4d_offset(pgdp, ea), ea);


Same kind of comments as already done apply to the rest.

Christophe

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