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KVM: arm64: Split kvm_pgtable_stage2_destroy()

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Split kvm_pgtable_stage2_destroy() into two:
  - kvm_pgtable_stage2_destroy_range(), that performs the
    page-table walk and free the entries over a range of addresses.
  - kvm_pgtable_stage2_destroy_pgd(), that frees the PGD.

This refactoring enables subsequent patches to free large page-tables
in chunks, calling cond_resched() between each chunk, to yield the
CPU as necessary.

Existing callers of kvm_pgtable_stage2_destroy(), that probably cannot
take advantage of this (such as nVMHE), will continue to function as is.

Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Suggested-by: Oliver Upton <oupton@kernel.org>
Link: https://msgid.link/20251113052452.975081-3-rananta@google.com
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Raghavendra Rao Ananta
2025-11-13 05:24:51 +00:00
committed by Oliver Upton
parent 156f70afcf
commit d68d66e57e
5 changed files with 73 additions and 9 deletions
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25
arch/arm64/kvm/hyp/pgtable.c
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@@ -1577,21 +1577,38 @@ static int stage2_free_walker(const struct kvm_pgtable_visit_ctx *ctx,
}
}
void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
void kvm_pgtable_stage2_destroy_range(struct kvm_pgtable *pgt,
u64 addr, u64 size)
{
size_t pgd_sz;
struct kvm_pgtable_walker walker = {
.cb = stage2_free_walker,
.flags = KVM_PGTABLE_WALK_LEAF |
KVM_PGTABLE_WALK_TABLE_POST,
};
WARN_ON(kvm_pgtable_walk(pgt, 0, BIT(pgt->ia_bits), &walker));
WARN_ON(kvm_pgtable_walk(pgt, addr, size, &walker));
}
void kvm_pgtable_stage2_destroy_pgd(struct kvm_pgtable *pgt)
{
size_t pgd_sz;
pgd_sz = kvm_pgd_pages(pgt->ia_bits, pgt->start_level) * PAGE_SIZE;
pgt->mm_ops->free_pages_exact(kvm_dereference_pteref(&walker, pgt->pgd), pgd_sz);
/*
* Since the pgtable is unlinked at this point, and not shared with
* other walkers, safely deference pgd with kvm_dereference_pteref_raw()
*/
pgt->mm_ops->free_pages_exact(kvm_dereference_pteref_raw(pgt->pgd), pgd_sz);
pgt->pgd = NULL;
}
void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
{
kvm_pgtable_stage2_destroy_range(pgt, 0, BIT(pgt->ia_bits));
kvm_pgtable_stage2_destroy_pgd(pgt);
}
void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, s8 level)
{
kvm_pteref_t ptep = (kvm_pteref_t)pgtable;