Re: [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@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Tested-by: Christophe Leroy <christophe.leroy@xxxxxx> # 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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