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author | Ricardo Koller <ricarkol@google.com> | 2023-04-26 20:23:24 +0300 |
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committer | Oliver Upton <oliver.upton@linux.dev> | 2023-05-16 20:39:18 +0300 |
commit | 8f5a3eb7513fc4deae511ce91af1c2c23874a8a7 (patch) | |
tree | 9e9b9dc3c3f9634856d41fd0e129e0798e5f8752 /arch/arm64/kvm/hyp/pgtable.c | |
parent | 2f440b72e852be428540579b5813ba2b8236578d (diff) | |
download | linux-8f5a3eb7513fc4deae511ce91af1c2c23874a8a7.tar.xz |
KVM: arm64: Add kvm_pgtable_stage2_split()
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).
Signed-off-by: Ricardo Koller <ricarkol@google.com>
Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Link: https://lore.kernel.org/r/20230426172330.1439644-7-ricarkol@google.com
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Diffstat (limited to 'arch/arm64/kvm/hyp/pgtable.c')
-rw-r--r-- | arch/arm64/kvm/hyp/pgtable.c | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c index 56edffc02bc6..8b03cd6fed12 100644 --- a/arch/arm64/kvm/hyp/pgtable.c +++ b/arch/arm64/kvm/hyp/pgtable.c @@ -1276,6 +1276,109 @@ kvm_pte_t *kvm_pgtable_stage2_create_unlinked(struct kvm_pgtable *pgt, return pgtable; } +/* + * Get the number of page-tables needed to replace a block with a + * fully populated tree up to the PTE entries. Note that @level is + * interpreted as in "level @level entry". + */ +static int stage2_block_get_nr_page_tables(u32 level) +{ + switch (level) { + case 1: + return PTRS_PER_PTE + 1; + case 2: + return 1; + case 3: + return 0; + default: + WARN_ON_ONCE(level < KVM_PGTABLE_MIN_BLOCK_LEVEL || + level >= KVM_PGTABLE_MAX_LEVELS); + 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 kvm_mmu_memory_cache *mc = ctx->arg; + struct kvm_s2_mmu *mmu; + kvm_pte_t pte = ctx->old, new, *childp; + enum kvm_pgtable_prot prot; + 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 (mc->nobjs >= nr_pages) { + /* Build a tree mapped down to the PTE granularity. */ + force_pte = true; + } else { + /* + * Don't force PTEs, so create_unlinked() below does + * not populate the tree up to the PTE level. The + * consequence is that the call will require a single + * page of level 2 entries at level 1, or a single + * page of PTEs at level 2. If we are at level 1, the + * PTEs will be created recursively. + */ + force_pte = false; + nr_pages = 1; + } + + if (mc->nobjs < nr_pages) + return -ENOMEM; + + mmu = container_of(mc, struct kvm_s2_mmu, split_page_cache); + phys = kvm_pte_to_phys(pte); + prot = kvm_pgtable_stage2_pte_prot(pte); + + childp = kvm_pgtable_stage2_create_unlinked(mmu->pgt, phys, + level, prot, mc, force_pte); + if (IS_ERR(childp)) + return PTR_ERR(childp); + + if (!stage2_try_break_pte(ctx, 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); + return 0; +} + +int kvm_pgtable_stage2_split(struct kvm_pgtable *pgt, u64 addr, u64 size, + struct kvm_mmu_memory_cache *mc) +{ + struct kvm_pgtable_walker walker = { + .cb = stage2_split_walker, + .flags = KVM_PGTABLE_WALK_LEAF, + .arg = mc, + }; + + 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, |