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KVM: s390: Fix gmap_link() 

The slow path of the fault handler ultimately called gmap_link(), which
assumed the fault was a major fault, and blindly called dat_link().

In case of minor faults, things were not always handled properly; in
particular the prefix and vsie marker bits were ignored.

Move dat_link() into gmap.c, renaming it accordingly. Once moved, the
new _gmap_link() function will be able to correctly honour the prefix
and vsie markers.

This will cause spurious unshadows in some uncommon cases.

Fixes: 94fd9b16cc ("KVM: s390: KVM page table management functions: lifecycle management")
Fixes: a2c17f9270 ("KVM: s390: New gmap code")
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
master
Claudio Imbrenda 2026-03-26 14:17:13 +01:00
parent 6f93d1ed6f
commit 45921d0212
3 changed files with 52 additions and 54 deletions
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48
arch/s390/kvm/dat.c
View File

@ -997,54 +997,6 @@ bool dat_test_age_gfn(union asce asce, gfn_t start, gfn_t end)
return _dat_walk_gfn_range(start, end, asce, &test_age_ops, 0, NULL) > 0;
}
int dat_link(struct kvm_s390_mmu_cache *mc, union asce asce, int level,
bool uses_skeys, struct guest_fault *f)
{
union crste oldval, newval;
union pte newpte, oldpte;
union pgste pgste;
int rc = 0;
rc = dat_entry_walk(mc, f->gfn, asce, DAT_WALK_ALLOC_CONTINUE, level, &f->crstep, &f->ptep);
if (rc == -EINVAL || rc == -ENOMEM)
return rc;
if (rc)
return -EAGAIN;
if (WARN_ON_ONCE(unlikely(get_level(f->crstep, f->ptep) > level)))
return -EINVAL;
if (f->ptep) {
pgste = pgste_get_lock(f->ptep);
oldpte = *f->ptep;
newpte = _pte(f->pfn, f->writable, f->write_attempt | oldpte.s.d, !f->page);
newpte.s.sd = oldpte.s.sd;
oldpte.s.sd = 0;
if (oldpte.val == _PTE_EMPTY.val || oldpte.h.pfra == f->pfn) {
pgste = __dat_ptep_xchg(f->ptep, pgste, newpte, f->gfn, asce, uses_skeys);
if (f->callback)
f->callback(f);
} else {
rc = -EAGAIN;
}
pgste_set_unlock(f->ptep, pgste);
} else {
oldval = READ_ONCE(*f->crstep);
newval = _crste_fc1(f->pfn, oldval.h.tt, f->writable,
f->write_attempt | oldval.s.fc1.d);
newval.s.fc1.sd = oldval.s.fc1.sd;
if (oldval.val != _CRSTE_EMPTY(oldval.h.tt).val &&
crste_origin_large(oldval) != crste_origin_large(newval))
return -EAGAIN;
if (!dat_crstep_xchg_atomic(f->crstep, oldval, newval, f->gfn, asce))
return -EAGAIN;
if (f->callback)
f->callback(f);
}
return rc;
}
static long dat_set_pn_crste(union crste *crstep, gfn_t gfn, gfn_t next, struct dat_walk *walk)
{
union crste newcrste, oldcrste;

2
arch/s390/kvm/dat.h
View File

@ -540,8 +540,6 @@ int dat_set_slot(struct kvm_s390_mmu_cache *mc, union asce asce, gfn_t start, gf
u16 type, u16 param);
int dat_set_prefix_notif_bit(union asce asce, gfn_t gfn);
bool dat_test_age_gfn(union asce asce, gfn_t start, gfn_t end);
int dat_link(struct kvm_s390_mmu_cache *mc, union asce asce, int level,
bool uses_skeys, struct guest_fault *f);
int dat_perform_essa(union asce asce, gfn_t gfn, int orc, union essa_state *state, bool *dirty);
long dat_reset_cmma(union asce asce, gfn_t start_gfn);

56
arch/s390/kvm/gmap.c
View File

@ -631,10 +631,60 @@ static inline bool gmap_1m_allowed(struct gmap *gmap, gfn_t gfn)
return test_bit(GMAP_FLAG_ALLOW_HPAGE_1M, &gmap->flags);
}
static int _gmap_link(struct kvm_s390_mmu_cache *mc, struct gmap *gmap, int level,
struct guest_fault *f)
{
union crste oldval, newval;
union pte newpte, oldpte;
union pgste pgste;
int rc = 0;
rc = dat_entry_walk(mc, f->gfn, gmap->asce, DAT_WALK_ALLOC_CONTINUE, level,
&f->crstep, &f->ptep);
if (rc == -ENOMEM)
return rc;
if (KVM_BUG_ON(rc == -EINVAL, gmap->kvm))
return rc;
if (rc)
return -EAGAIN;
if (KVM_BUG_ON(get_level(f->crstep, f->ptep) > level, gmap->kvm))
return -EINVAL;
if (f->ptep) {
pgste = pgste_get_lock(f->ptep);
oldpte = *f->ptep;
newpte = _pte(f->pfn, f->writable, f->write_attempt | oldpte.s.d, !f->page);
newpte.s.sd = oldpte.s.sd;
oldpte.s.sd = 0;
if (oldpte.val == _PTE_EMPTY.val || oldpte.h.pfra == f->pfn) {
pgste = gmap_ptep_xchg(gmap, f->ptep, newpte, pgste, f->gfn);
if (f->callback)
f->callback(f);
} else {
rc = -EAGAIN;
}
pgste_set_unlock(f->ptep, pgste);
} else {
do {
oldval = READ_ONCE(*f->crstep);
newval = _crste_fc1(f->pfn, oldval.h.tt, f->writable,
f->write_attempt | oldval.s.fc1.d);
newval.s.fc1.sd = oldval.s.fc1.sd;
if (oldval.val != _CRSTE_EMPTY(oldval.h.tt).val &&
crste_origin_large(oldval) != crste_origin_large(newval))
return -EAGAIN;
} while (!gmap_crstep_xchg_atomic(gmap, f->crstep, oldval, newval, f->gfn));
if (f->callback)
f->callback(f);
}
return rc;
}
int gmap_link(struct kvm_s390_mmu_cache *mc, struct gmap *gmap, struct guest_fault *f)
{
unsigned int order;
int rc, level;
int level;
lockdep_assert_held(&gmap->kvm->mmu_lock);
@ -646,9 +696,7 @@ int gmap_link(struct kvm_s390_mmu_cache *mc, struct gmap *gmap, struct guest_fau
else if (order >= get_order(_SEGMENT_SIZE) && gmap_1m_allowed(gmap, f->gfn))
level = TABLE_TYPE_SEGMENT;
}
rc = dat_link(mc, gmap->asce, level, uses_skeys(gmap), f);
KVM_BUG_ON(rc == -EINVAL, gmap->kvm);
return rc;
return _gmap_link(mc, gmap, level, f);
}
static int gmap_ucas_map_one(struct kvm_s390_mmu_cache *mc, struct gmap *gmap,