| Message ID | 20230301210928.565562-5-ricarkol@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Implement Eager Page Splitting for ARM | expand |
On 3/2/23 05:09, Ricardo Koller wrote: > Add a new stage2 function, kvm_pgtable_stage2_split(), for splitting a > range of huge pages. This will be used for eager-splitting huge pages > into PAGE_SIZE pages. The goal is to avoid having to split huge pages > on write-protection faults, and instead use this function to do it > ahead of time for large ranges (e.g., all guest memory in 1G chunks at > a time). > > No functional change intended. This new function will be used in a > subsequent commit. > > Signed-off-by: Ricardo Koller <ricarkol@google.com> Reviewed-by: Shaoqin Huang <shahuang@redhat.com> > --- > arch/arm64/include/asm/kvm_pgtable.h | 30 +++++++ > arch/arm64/kvm/hyp/pgtable.c | 113 +++++++++++++++++++++++++++ > 2 files changed, 143 insertions(+) > > diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h > index 2b98357a5497..ce0a8e17fb6d 100644 > --- a/arch/arm64/include/asm/kvm_pgtable.h > +++ b/arch/arm64/include/asm/kvm_pgtable.h > @@ -657,6 +657,36 @@ bool kvm_pgtable_stage2_is_young(struct kvm_pgtable *pgt, u64 addr); > */ > int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size); > > +/** > + * kvm_pgtable_stage2_split() - Split a range of huge pages into leaf PTEs pointing > + * to PAGE_SIZE guest pages. > + * @pgt: Page-table structure initialised by kvm_pgtable_stage2_init(). > + * @addr: Intermediate physical address from which to split. > + * @size: Size of the range. > + * @mc: Cache of pre-allocated and zeroed memory from which to allocate > + * page-table pages. > + * @mc_capacity: Number of pages in @mc. > + * > + * @addr and the end (@addr + @size) are effectively aligned down and up to > + * the top level huge-page block size. This is an example using 1GB > + * huge-pages and 4KB granules. > + * > + * [---input range---] > + * : : > + * [--1G block pte--][--1G block pte--][--1G block pte--][--1G block pte--] > + * : : > + * [--2MB--][--2MB--][--2MB--][--2MB--] > + * : : > + * [ ][ ][:][ ][ ][ ][ ][ ][:][ ][ ][ ] > + * : : > + * > + * Return: 0 on success, negative error code on failure. Note that > + * kvm_pgtable_stage2_split() is best effort: it tries to break as many > + * blocks in the input range as allowed by @mc_capacity. > + */ > +int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size, > + void *mc, u64 mc_capacity); > + > /** > * kvm_pgtable_walk() - Walk a page-table. > * @pgt: Page-table structure initialised by kvm_pgtable_*_init(). > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c > index 3554b74e13c6..75726edba2f3 100644 > --- a/arch/arm64/kvm/hyp/pgtable.c > +++ b/arch/arm64/kvm/hyp/pgtable.c > @@ -1228,6 +1228,119 @@ kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt, > return pgtable; > } > > +struct stage2_split_data { > + struct kvm_s2_mmu *mmu; > + void *memcache; > + u64 mc_capacity; > +}; > + > +/* > + * Get the number of page-tables needed to replace a block with a > + * fully populated tree, up to the PTE level, at particular level. > + */ > +static inline int stage2_block_get_nr_page_tables(u32 level) > +{ > + if (WARN_ON_ONCE(level < KVM_PGTABLE_MIN_BLOCK_LEVEL || > + level >= KVM_PGTABLE_MAX_LEVELS)) > + return -EINVAL; > + > + switch (level) { > + case 1: > + return PTRS_PER_PTE + 1; > + case 2: > + return 1; > + case 3: > + return 0; > + default: > + return -EINVAL; > + }; > +} > + > +static int stage2_split_walker(const struct kvm_pgtable_visit_ctx *ctx, > + enum kvm_pgtable_walk_flags visit) > +{ > + struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; > + struct stage2_split_data *data = ctx->arg; > + kvm_pte_t pte = ctx->old, new, *childp; > + enum kvm_pgtable_prot prot; > + void *mc = data->memcache; > + u32 level = ctx->level; > + bool force_pte; > + int nr_pages; > + u64 phys; > + > + /* No huge-pages exist at the last level */ > + if (level == KVM_PGTABLE_MAX_LEVELS - 1) > + return 0; > + > + /* We only split valid block mappings */ > + if (!kvm_pte_valid(pte)) > + return 0; > + > + nr_pages = stage2_block_get_nr_page_tables(level); > + if (nr_pages < 0) > + return nr_pages; > + > + if (data->mc_capacity >= nr_pages) { > + /* Build a tree mapped down to the PTE granularity. */ > + force_pte = true; > + } else { > + /* > + * Don't force PTEs. This requires a single page of PMDs at the > + * PUD level, or a single page of PTEs at the PMD level. If we > + * are at the PUD level, the PTEs will be created recursively. > + */ > + force_pte = false; > + nr_pages = 1; > + } > + > + if (data->mc_capacity < nr_pages) > + return -ENOMEM; > + > + phys = kvm_pte_to_phys(pte); > + prot = kvm_pgtable_stage2_pte_prot(pte); > + > + childp = kvm_pgtable_stage2_create_unlinked(data->mmu->pgt, phys, > + level, prot, mc, force_pte); > + if (IS_ERR(childp)) > + return PTR_ERR(childp); > + > + if (!stage2_try_break_pte(ctx, data->mmu)) { > + kvm_pgtable_stage2_free_unlinked(mm_ops, childp, level); > + mm_ops->put_page(childp); > + return -EAGAIN; > + } > + > + /* > + * Note, the contents of the page table are guaranteed to be made > + * visible before the new PTE is assigned because stage2_make_pte() > + * writes the PTE using smp_store_release(). > + */ > + new = kvm_init_table_pte(childp, mm_ops); > + stage2_make_pte(ctx, new); > + dsb(ishst); > + data->mc_capacity -= nr_pages; > + return 0; > +} > + > +int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size, > + void *mc, u64 mc_capacity) > +{ > + struct stage2_split_data split_data = { > + .mmu = pgt->mmu, > + .memcache = mc, > + .mc_capacity = mc_capacity, > + }; > + > + struct kvm_pgtable_walker walker = { > + .cb = stage2_split_walker, > + .flags = KVM_PGTABLE_WALK_LEAF, > + .arg = &split_data, > + }; > + > + return kvm_pgtable_walk(pgt, addr, size, &walker); > +} > + > int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu, > struct kvm_pgtable_mm_ops *mm_ops, > enum kvm_pgtable_stage2_flags flags,
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h index 2b98357a5497..ce0a8e17fb6d 100644 --- a/arch/arm64/include/asm/kvm_pgtable.h +++ b/arch/arm64/include/asm/kvm_pgtable.h @@ -657,6 +657,36 @@ bool kvm_pgtable_stage2_is_young(struct kvm_pgtable *pgt, u64 addr); */ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size); +/** + * kvm_pgtable_stage2_split() - Split a range of huge pages into leaf PTEs pointing + * to PAGE_SIZE guest pages. + * @pgt: Page-table structure initialised by kvm_pgtable_stage2_init(). + * @addr: Intermediate physical address from which to split. + * @size: Size of the range. + * @mc: Cache of pre-allocated and zeroed memory from which to allocate + * page-table pages. + * @mc_capacity: Number of pages in @mc. + * + * @addr and the end (@addr + @size) are effectively aligned down and up to + * the top level huge-page block size. This is an example using 1GB + * huge-pages and 4KB granules. + * + * [---input range---] + * : : + * [--1G block pte--][--1G block pte--][--1G block pte--][--1G block pte--] + * : : + * [--2MB--][--2MB--][--2MB--][--2MB--] + * : : + * [ ][ ][:][ ][ ][ ][ ][ ][:][ ][ ][ ] + * : : + * + * Return: 0 on success, negative error code on failure. Note that + * kvm_pgtable_stage2_split() is best effort: it tries to break as many + * blocks in the input range as allowed by @mc_capacity. + */ +int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size, + void *mc, u64 mc_capacity); + /** * kvm_pgtable_walk() - Walk a page-table. * @pgt: Page-table structure initialised by kvm_pgtable_*_init(). diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 3554b74e13c6..75726edba2f3 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -1228,6 +1228,119 @@ kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt, return pgtable; } +struct stage2_split_data { + struct kvm_s2_mmu *mmu; + void *memcache; + u64 mc_capacity; +}; + +/* + * Get the number of page-tables needed to replace a block with a + * fully populated tree, up to the PTE level, at particular level. + */ +static inline int stage2_block_get_nr_page_tables(u32 level) +{ + if (WARN_ON_ONCE(level < KVM_PGTABLE_MIN_BLOCK_LEVEL || + level >= KVM_PGTABLE_MAX_LEVELS)) + return -EINVAL; + + switch (level) { + case 1: + return PTRS_PER_PTE + 1; + case 2: + return 1; + case 3: + return 0; + default: + return -EINVAL; + }; +} + +static int stage2_split_walker(const struct kvm_pgtable_visit_ctx *ctx, + enum kvm_pgtable_walk_flags visit) +{ + struct kvm_pgtable_mm_ops *mm_ops = ctx->mm_ops; + struct stage2_split_data *data = ctx->arg; + kvm_pte_t pte = ctx->old, new, *childp; + enum kvm_pgtable_prot prot; + void *mc = data->memcache; + u32 level = ctx->level; + bool force_pte; + int nr_pages; + u64 phys; + + /* No huge-pages exist at the last level */ + if (level == KVM_PGTABLE_MAX_LEVELS - 1) + return 0; + + /* We only split valid block mappings */ + if (!kvm_pte_valid(pte)) + return 0; + + nr_pages = stage2_block_get_nr_page_tables(level); + if (nr_pages < 0) + return nr_pages; + + if (data->mc_capacity >= nr_pages) { + /* Build a tree mapped down to the PTE granularity. */ + force_pte = true; + } else { + /* + * Don't force PTEs. This requires a single page of PMDs at the + * PUD level, or a single page of PTEs at the PMD level. If we + * are at the PUD level, the PTEs will be created recursively. + */ + force_pte = false; + nr_pages = 1; + } + + if (data->mc_capacity < nr_pages) + return -ENOMEM; + + phys = kvm_pte_to_phys(pte); + prot = kvm_pgtable_stage2_pte_prot(pte); + + childp = kvm_pgtable_stage2_create_unlinked(data->mmu->pgt, phys, + level, prot, mc, force_pte); + if (IS_ERR(childp)) + return PTR_ERR(childp); + + if (!stage2_try_break_pte(ctx, data->mmu)) { + kvm_pgtable_stage2_free_unlinked(mm_ops, childp, level); + mm_ops->put_page(childp); + return -EAGAIN; + } + + /* + * Note, the contents of the page table are guaranteed to be made + * visible before the new PTE is assigned because stage2_make_pte() + * writes the PTE using smp_store_release(). + */ + new = kvm_init_table_pte(childp, mm_ops); + stage2_make_pte(ctx, new); + dsb(ishst); + data->mc_capacity -= nr_pages; + return 0; +} + +int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size, + void *mc, u64 mc_capacity) +{ + struct stage2_split_data split_data = { + .mmu = pgt->mmu, + .memcache = mc, + .mc_capacity = mc_capacity, + }; + + struct kvm_pgtable_walker walker = { + .cb = stage2_split_walker, + .flags = KVM_PGTABLE_WALK_LEAF, + .arg = &split_data, + }; + + return kvm_pgtable_walk(pgt, addr, size, &walker); +} + int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu, struct kvm_pgtable_mm_ops *mm_ops, enum kvm_pgtable_stage2_flags flags,
Add a new stage2 function, kvm_pgtable_stage2_split(), for splitting a range of huge pages. This will be used for eager-splitting huge pages into PAGE_SIZE pages. The goal is to avoid having to split huge pages on write-protection faults, and instead use this function to do it ahead of time for large ranges (e.g., all guest memory in 1G chunks at a time). No functional change intended. This new function will be used in a subsequent commit. Signed-off-by: Ricardo Koller <ricarkol@google.com> --- arch/arm64/include/asm/kvm_pgtable.h | 30 +++++++ arch/arm64/kvm/hyp/pgtable.c | 113 +++++++++++++++++++++++++++ 2 files changed, 143 insertions(+)