From: Claudio Imbrenda Date: Wed, 27 May 2026 14:43:54 +0000 (+0200) Subject: KVM: s390: Track page size in struct guest_fault X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=499d2e4b75c44365a40a5fe623f3bd5bc1844197;p=thirdparty%2Flinux.git KVM: s390: Track page size in struct guest_fault Until now, the members of struct guest_fault are always accessed while holding the required locks, and thus the ptep and crstep pointers can be dereferenced safely. There will be some new cases where callers of kvm_s390_faultin_gfn() need to know the size of the page used to solve the fault, at which point no locks are held anymore, and dereferencing the crstep field is not possible. Introduce a new crste_region3 flag for struct guest_fault to indicate whether the crstep used to solve the fault was a region 3 entry with FC=1 (large pud). This allows to disambiguate all three possible scenarios: * If ptep is not NULL, the fault was solved with a pte. * If ptep is NULL and crste_region3 is 0, a segment entry with FC=1 (large pmd) was used. * If ptep is NULL and crste_region3 is 1, a region 3 entry with FC=1 (large pud) was used. Reviewed-by: Steffen Eiden Signed-off-by: Claudio Imbrenda Message-ID: <20260527144358.186359-2-imbrenda@linux.ibm.com> --- diff --git a/arch/s390/kvm/dat.h b/arch/s390/kvm/dat.h index 8f8278c448794..5d848e74e3828 100644 --- a/arch/s390/kvm/dat.h +++ b/arch/s390/kvm/dat.h @@ -500,6 +500,7 @@ struct guest_fault { bool write_attempt; /* Write access attempted */ bool attempt_pfault; /* Attempt a pfault first */ bool valid; /* This entry contains valid data */ + bool crste_region3; /* Whether crstep refers to a region3 entry */ void (*callback)(struct guest_fault *f); void *priv; }; diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c index 3c26e35af0ef7..fe138d17caaf3 100644 --- a/arch/s390/kvm/gmap.c +++ b/arch/s390/kvm/gmap.c @@ -531,6 +531,7 @@ static int gmap_handle_minor_crste_fault(struct gmap *gmap, struct guest_fault * f->pfn = PHYS_PFN(large_crste_to_phys(oldcrste, f->gfn)); f->writable = oldcrste.s.fc1.w; + f->crste_region3 = is_pud(oldcrste); /* Appropriate permissions already (race with another handler), nothing to do. */ if (!oldcrste.h.i && !(f->write_attempt && oldcrste.h.p)) return 0; @@ -690,6 +691,7 @@ static int _gmap_link(struct kvm_s390_mmu_cache *mc, struct gmap *gmap, int leve if (oldval.val != _CRSTE_EMPTY(oldval.h.tt).val && crste_origin_large(oldval) != crste_origin_large(newval)) return -EAGAIN; + f->crste_region3 = is_pud(newval); } while (!gmap_crstep_xchg_atomic(gmap, f->crstep, oldval, newval, f->gfn)); if (f->callback) f->callback(f);