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Wed, 25 Mar 2026 17:13:13 +0000 (GMT) From: Claudio Imbrenda To: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, nrb@linux.ibm.com, seiden@linux.ibm.com, gra@linux.ibm.com, schlameuss@linux.ibm.com, hca@linux.ibm.com, david@kernel.org Subject: [PATCH v4 05/10] KVM: s390: Correctly handle guest mappings without struct page Date: Wed, 25 Mar 2026 18:13:06 +0100 Message-ID: <20260325171311.182210-6-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260325171311.182210-1-imbrenda@linux.ibm.com> References: <20260325171311.182210-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Proofpoint-GUID: n1Yv5DFcZ_ChFMSf5u9YuUPwqvADQHyc X-Proofpoint-ORIG-GUID: n1Yv5DFcZ_ChFMSf5u9YuUPwqvADQHyc X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzI1MDEyMSBTYWx0ZWRfX7BqS9aT8pAd8 IQTE5d7b77gfSFNwGC6KmdiWWGVjrexhWESBNdtu8+H2PbDbNh8rcULRPg3ScYOPjqFPIcFlCi0 9aOp8LkPA04L4B+ISneGstS5altUX7oPbtokBq1Upe4Xs4n6zsEepbfVXiTd2F/kTRu7Ngcgu/p 7hTTJVTzei8YKmLYz+ia66/+SqQUUTVUQdHZl9f3fSQ6w5LHjm4OiWQOaCy5RLF170Ihd7OGjMD fe+cOFZqeSgMyPZb9Ao2z4Q0P2MJJ+gRRNB7KIiBLeD3ImUgeFWcSZOi23HTbhHsXDiNIUer1fV NiwwG9AThdBsXIUmfzSKljKJOQzsn7K98iZmn+VK0rkCnpaHjhdaQD1aWdC4A12w6fZzG98pG+t z4bOiquZKjDo2eRcL1ehk4CnBmZUUEGmL5WimuOFnvYMHssnWKxYc9XGsmIAxCNNrMIL09gZ/mR x3bWMlbBbIxgS5qD8dQ== X-Authority-Analysis: v=2.4 cv=KbXfcAYD c=1 sm=1 tr=0 ts=69c417ad cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=x4-NZlbSC-zwRaKax1cA:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-25_05,2026-03-24_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 impostorscore=0 malwarescore=0 adultscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2603250121 Content-Type: text/plain; charset="utf-8" Introduce a new special softbit for large pages, like already presend for normal pages, and use it to mark guest mappings that do not have struct pages. Whenever a leaf DAT entry becomes dirty, check the special softbit and only call SetPageDirty() if there is an actual struct page. Move the logic to mark pages dirty inside _gmap_ptep_xchg() and _gmap_crstep_xchg_atomic(), to avoid needlessly duplicating the code. Signed-off-by: Claudio Imbrenda Fixes: 5a74e3d93417 ("KVM: s390: KVM-specific bitfields and helper function= s") Fixes: a2c17f9270cc ("KVM: s390: New gmap code") --- arch/s390/kvm/dat.h | 12 ++++++------ arch/s390/kvm/gmap.c | 5 +---- arch/s390/kvm/gmap.h | 4 ++++ 3 files changed, 11 insertions(+), 10 deletions(-) diff --git a/arch/s390/kvm/dat.h b/arch/s390/kvm/dat.h index efedcf96110c..874cc962e196 100644 --- a/arch/s390/kvm/dat.h +++ b/arch/s390/kvm/dat.h @@ -160,14 +160,14 @@ union pmd { unsigned long :44; /* HW */ unsigned long : 3; /* Unused */ unsigned long : 1; /* HW */ + unsigned long s : 1; /* Special */ unsigned long w : 1; /* Writable soft-bit */ unsigned long r : 1; /* Readable soft-bit */ unsigned long d : 1; /* Dirty */ unsigned long y : 1; /* Young */ - unsigned long prefix_notif : 1; /* Guest prefix invalidation notificati= on */ unsigned long : 3; /* HW */ + unsigned long prefix_notif : 1; /* Guest prefix invalidation notificati= on */ unsigned long vsie_notif : 1; /* Referenced in a shadow table */ - unsigned long : 1; /* Unused */ unsigned long : 4; /* HW */ unsigned long sd : 1; /* Soft-Dirty */ unsigned long pr : 1; /* Present */ @@ -183,14 +183,14 @@ union pud { unsigned long :33; /* HW */ unsigned long :14; /* Unused */ unsigned long : 1; /* HW */ + unsigned long s : 1; /* Special */ unsigned long w : 1; /* Writable soft-bit */ unsigned long r : 1; /* Readable soft-bit */ unsigned long d : 1; /* Dirty */ unsigned long y : 1; /* Young */ - unsigned long prefix_notif : 1; /* Guest prefix invalidation notificati= on */ unsigned long : 3; /* HW */ + unsigned long prefix_notif : 1; /* Guest prefix invalidation notificati= on */ unsigned long vsie_notif : 1; /* Referenced in a shadow table */ - unsigned long : 1; /* Unused */ unsigned long : 4; /* HW */ unsigned long sd : 1; /* Soft-Dirty */ unsigned long pr : 1; /* Present */ @@ -254,14 +254,14 @@ union crste { struct { unsigned long :47; unsigned long : 1; /* HW (should be 0) */ + unsigned long s : 1; /* Special */ unsigned long w : 1; /* Writable */ unsigned long r : 1; /* Readable */ unsigned long d : 1; /* Dirty */ unsigned long y : 1; /* Young */ - unsigned long prefix_notif : 1; /* Guest prefix invalidation notificati= on */ unsigned long : 3; /* HW */ + unsigned long prefix_notif : 1; /* Guest prefix invalidation notificati= on */ unsigned long vsie_notif : 1; /* Referenced in a shadow table */ - unsigned long : 1; unsigned long : 4; /* HW */ unsigned long sd : 1; /* Soft-Dirty */ unsigned long pr : 1; /* Present */ diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c index 03e15b5e0b9a..e9fc471a5141 100644 --- a/arch/s390/kvm/gmap.c +++ b/arch/s390/kvm/gmap.c @@ -544,8 +544,6 @@ static int gmap_handle_minor_crste_fault(union asce asc= e, struct guest_fault *f) newcrste.s.fc1.d =3D 1; newcrste.s.fc1.sd =3D 1; } - if (!oldcrste.s.fc1.d && newcrste.s.fc1.d) - SetPageDirty(phys_to_page(crste_origin_large(newcrste))); /* In case of races, let the slow path deal with it. */ return !dat_crstep_xchg_atomic(f->crstep, oldcrste, newcrste, f->gfn, as= ce); } @@ -576,8 +574,6 @@ static int _gmap_handle_minor_pte_fault(struct gmap *gm= ap, union pgste *pgste, newpte.s.d =3D 1; newpte.s.sd =3D 1; } - if (!oldpte.s.d && newpte.s.d) - SetPageDirty(pfn_to_page(newpte.h.pfra)); *pgste =3D gmap_ptep_xchg(gmap, f->ptep, newpte, *pgste, f->gfn); =20 return 0; @@ -669,6 +665,7 @@ static int _gmap_link(struct kvm_s390_mmu_cache *mc, st= ruct gmap *gmap, int leve oldval =3D READ_ONCE(*f->crstep); newval =3D _crste_fc1(f->pfn, oldval.h.tt, f->writable, f->write_attempt | oldval.s.fc1.d); + newval.s.fc1.s =3D !f->page; newval.s.fc1.sd =3D oldval.s.fc1.sd; if (oldval.val !=3D _CRSTE_EMPTY(oldval.h.tt).val && crste_origin_large(oldval) !=3D crste_origin_large(newval)) diff --git a/arch/s390/kvm/gmap.h b/arch/s390/kvm/gmap.h index 150e91e15ee0..1b900819bab2 100644 --- a/arch/s390/kvm/gmap.h +++ b/arch/s390/kvm/gmap.h @@ -185,6 +185,8 @@ static inline union pgste _gmap_ptep_xchg(struct gmap *= gmap, union pte *ptep, un else _gmap_handle_vsie_unshadow_event(gmap, gfn); } + if (!ptep->s.d && newpte.s.d && !ptep->s.s) + SetPageDirty(pfn_to_page(newpte.h.pfra)); return __dat_ptep_xchg(ptep, pgste, newpte, gfn, gmap->asce, uses_skeys(g= map)); } =20 @@ -220,6 +222,8 @@ static inline bool __must_check _gmap_crstep_xchg_atomi= c(struct gmap *gmap, unio else _gmap_handle_vsie_unshadow_event(gmap, gfn); } + if (!oldcrste.s.fc1.d && newcrste.s.fc1.d && !oldcrste.s.fc1.s) + SetPageDirty(phys_to_page(crste_origin_large(newcrste))); return dat_crstep_xchg_atomic(crstep, oldcrste, newcrste, gfn, gmap->asce= ); } =20 --=20 2.53.0