Re: [PATCH v2 07/13] powerpc: add support for folded p4d page tables

From: Christophe Leroy
Date: Sun Feb 16 2020 - 05:41:17 EST

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Le 16/02/2020 Ã 09:18, Mike Rapoport a ÃcritÂ:

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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