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KVM: s390: cmma: Fix dirty tracking when removing memslot

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When a memslot is removed, all ptes that mapped the slot are cleared or
even deallocated. If this happens while the system is in migration
mode, and if cmma-dirty pages are removed, the cmma-dirty counter will
not reflect reality.

Fix by appropriately decrementing the cmma-dirty counter when removing
a memslot.

Opportunistically improve kvm_arch_commit_memory_region() to use
__free() for the struct kvm_s390_mmu_cache.

Fixes: e38c884df9 ("KVM: s390: Switch to new gmap")
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260803124040.126471-9-imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2026-08-03 14:40:35 +02:00
parent 4db7207052
commit ec21534627
2 changed files with 29 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/s390/kvm/dat.c
View File

@ -850,6 +850,7 @@ static long _dat_slot_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_wal
struct slot_priv *p = walk->priv;
union crste dummy = { .val = p->token };
union pte new_pte, pte = READ_ONCE(*ptep);
union pgste pgste;
new_pte = _PTE_TOK(dummy.tok.type, dummy.tok.par);
@ -857,7 +858,11 @@ static long _dat_slot_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_wal
if (pte.val == new_pte.val)
return 0;
dat_ptep_xchg(ptep, new_pte, gfn, walk->asce, false);
pgste = pgste_get_lock(ptep);
pgste = __dat_ptep_xchg(ptep, pgste, new_pte, gfn, walk->asce, false);
pgste.cmma_d = 0;
pgste_set_unlock(ptep, pgste);
return 0;
}

25
arch/s390/kvm/kvm-s390.c
View File

@ -5812,14 +5812,30 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
return 0;
}
static long cmma_d_count_pte(union pte *ptep, gfn_t gfn, gfn_t next, struct dat_walk *walk)
{
union pgste pgste;
pgste = pgste_get_lock(ptep);
if (pgste.cmma_d) {
pgste.cmma_d = 0;
atomic64_dec(walk->priv);
}
pgste_set_unlock(ptep, pgste);
return 0;
}
void kvm_arch_commit_memory_region(struct kvm *kvm,
struct kvm_memory_slot *old,
const struct kvm_memory_slot *new,
enum kvm_mr_change change)
{
struct kvm_s390_mmu_cache *mc = NULL;
const struct dat_walk_ops ops = { .pte_entry = cmma_d_count_pte, };
struct kvm_s390_mmu_cache *mc __free(kvm_s390_mmu_cache) = NULL;
int rc = 0;
guard(mutex)(&kvm->slots_arch_lock);
if (change == KVM_MR_FLAGS_ONLY)
return;
@ -5830,6 +5846,12 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
}
scoped_guard(write_lock, &kvm->mmu_lock) {
if (kvm->arch.migration_mode && kvm->arch.use_cmma && old) {
_dat_walk_gfn_range(old->base_gfn, old->base_gfn + old->npages,
kvm->arch.gmap->asce, &ops, DAT_WALK_IGN_HOLES,
&kvm->arch.cmma_dirty_pages);
}
switch (change) {
case KVM_MR_DELETE:
rc = dat_delete_slot(mc, kvm->arch.gmap->asce, old->base_gfn, old->npages);
@ -5851,7 +5873,6 @@ void kvm_arch_commit_memory_region(struct kvm *kvm,
out:
if (rc)
pr_warn("failed to commit memory region\n");
kvm_s390_free_mmu_cache(mc);
return;
}