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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
Download Patch File Download Diff File Expand all files Collapse all files

30
arch/arm64/include/asm/kvm_pgtable.h
View File

@@ -355,6 +355,11 @@ static inline kvm_pte_t *kvm_dereference_pteref(struct kvm_pgtable_walker *walke
return pteref;
}
static inline kvm_pte_t *kvm_dereference_pteref_raw(kvm_pteref_t pteref)
{
return pteref;
}
static inline int kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker)
{
/*
@@ -384,6 +389,11 @@ static inline kvm_pte_t *kvm_dereference_pteref(struct kvm_pgtable_walker *walke
return rcu_dereference_check(pteref, !(walker->flags & KVM_PGTABLE_WALK_SHARED));
}
static inline kvm_pte_t *kvm_dereference_pteref_raw(kvm_pteref_t pteref)
{
return rcu_dereference_raw(pteref);
}
static inline int kvm_pgtable_walk_begin(struct kvm_pgtable_walker *walker)
{
if (walker->flags & KVM_PGTABLE_WALK_SHARED)
@@ -551,6 +561,26 @@ static inline int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2
*/
void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
/**
* kvm_pgtable_stage2_destroy_range() - Destroy the unlinked range of addresses.
* @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
* @addr: Intermediate physical address at which to place the mapping.
* @size: Size of the mapping.
*
* The page-table is assumed to be unreachable by any hardware walkers prior
* to freeing and therefore no TLB invalidation is performed.
*/
void kvm_pgtable_stage2_destroy_range(struct kvm_pgtable *pgt,
u64 addr, u64 size);
/**
* kvm_pgtable_stage2_destroy_pgd() - Destroy the PGD of guest stage-2 page-table.
* @pgt: Page-table structure initialised by kvm_pgtable_stage2_init*().
*
* It is assumed that the rest of the page-table is freed before this operation.
*/
void kvm_pgtable_stage2_destroy_pgd(struct kvm_pgtable *pgt);
/**
* kvm_pgtable_stage2_free_unlinked() - Free an unlinked stage-2 paging structure.
* @mm_ops: Memory management callbacks.

4
arch/arm64/include/asm/kvm_pkvm.h
View File

@@ -180,7 +180,9 @@ struct pkvm_mapping {
int pkvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu,
struct kvm_pgtable_mm_ops *mm_ops);
void pkvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
void pkvm_pgtable_stage2_destroy_range(struct kvm_pgtable *pgt,
u64 addr, u64 size);
void pkvm_pgtable_stage2_destroy_pgd(struct kvm_pgtable *pgt);
int pkvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
enum kvm_pgtable_prot prot, void *mc,
enum kvm_pgtable_walk_flags flags);

25
arch/arm64/kvm/hyp/pgtable.c
View File

@@ -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;

12
arch/arm64/kvm/mmu.c
View File

@@ -904,6 +904,14 @@ static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
return 0;
}
static void kvm_stage2_destroy(struct kvm_pgtable *pgt)
{
unsigned int ia_bits = VTCR_EL2_IPA(pgt->mmu->vtcr);
KVM_PGT_FN(kvm_pgtable_stage2_destroy_range)(pgt, 0, BIT(ia_bits));
KVM_PGT_FN(kvm_pgtable_stage2_destroy_pgd)(pgt);
}
/**
* kvm_init_stage2_mmu - Initialise a S2 MMU structure
* @kvm: The pointer to the KVM structure
@@ -980,7 +988,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
return 0;
out_destroy_pgtable:
KVM_PGT_FN(kvm_pgtable_stage2_destroy)(pgt);
kvm_stage2_destroy(pgt);
out_free_pgtable:
kfree(pgt);
return err;
@@ -1081,7 +1089,7 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
write_unlock(&kvm->mmu_lock);
if (pgt) {
KVM_PGT_FN(kvm_pgtable_stage2_destroy)(pgt);
kvm_stage2_destroy(pgt);
kfree(pgt);
}
}

11
arch/arm64/kvm/pkvm.c
View File

@@ -344,9 +344,16 @@ static int __pkvm_pgtable_stage2_unmap(struct kvm_pgtable *pgt, u64 start, u64 e
return 0;
}
void pkvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
void pkvm_pgtable_stage2_destroy_range(struct kvm_pgtable *pgt,
u64 addr, u64 size)
{
__pkvm_pgtable_stage2_unmap(pgt, 0, ~(0ULL));
__pkvm_pgtable_stage2_unmap(pgt, addr, addr + size);
}
void pkvm_pgtable_stage2_destroy_pgd(struct kvm_pgtable *pgt)
{
/* Expected to be called after all pKVM mappings have been released. */
WARN_ON_ONCE(!RB_EMPTY_ROOT(&pgt->pkvm_mappings.rb_root));
}
int pkvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,