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Wed, 6 May 2026 14:12:00 +0000 (GMT) From: Claudio Imbrenda To: linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, frankja@linux.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com Subject: [PATCH v1 3/3] KVM: s390: vsie: Fix unshadowing logic Date: Wed, 6 May 2026 16:11:59 +0200 Message-ID: <20260506141159.154240-4-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260506141159.154240-1-imbrenda@linux.ibm.com> References: <20260506141159.154240-1-imbrenda@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=XPQAjwhE c=1 sm=1 tr=0 ts=69fb4c37 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=Ww7HMaUJomrHWgeF4nUA:9 X-Proofpoint-ORIG-GUID: k10qdcYFr75xG3EjYB18BhP2rQbZTOb4 X-Proofpoint-GUID: k10qdcYFr75xG3EjYB18BhP2rQbZTOb4 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA2MDEzOSBTYWx0ZWRfXz1kztoRrKlBL DikW+M3vurUoZAfKIi+GPpjoPop9XaesyApvlaMzMDyCS09h2MhZqxur/xPIBwWMM3zP2dgt+fs Z7PRnTAmXGARQPjcXh8jf1ZRezY5Tjp3cU8kk/JzutHw5Je926DprQtVhu8ulRg8nDp1U7G9z6Y Ys2KOdysFEfMcXGufOdZzRFm2ZfNTLhJryHXGmCD/D0ggBVNq0eZlxk4+iQ9O/wwvL7RHh0NEV2 rIoP8wFgTstYN7QVRTHUftz9gY6+NcBbxCc4Tv74n9vFjkPdV9jQo7Ttm4/5AxBJ4ZRb/nAJAWq SoPwF1Y0aI2gpfcq+x168zGC4NQB6UjP0PwsryAqFjC/mlKPXHN9+toxECPtJxTQOmsIfuP51Y8 mtj+qtOfgGz917UGwBOObKyq8nJne4JlXO7CLCAfuI8FqS9COcdyReyPH+CPuhRaJ8r7d1ZpN2e VvRf3iChu9HyUYTFvYA== 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=2026-05-05_03,2026-05-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 adultscore=0 spamscore=0 priorityscore=1501 impostorscore=0 phishscore=0 malwarescore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604200000 definitions=main-2605060139 In some cases (i.e. under extreme memory pressure on the host), attempting to shadow memory will result in the same memory being unshadowed, causing a loop. Add a PGSTE bit to distinguish between shadowed memory and shadowed DAT tables, fix the unshadowing logic in _gmap_ptep_xchg() to prevent unnecessary unshadowing and perform better checks. Also fix the unshadowing logic in _gmap_crstep_xchg_atomic() which did not unshadow properly when the large page would become unprotected. Signed-off-by: Claudio Imbrenda Fixes: a2c17f9270cc ("KVM: s390: New gmap code") --- arch/s390/kvm/dat.h | 3 ++- arch/s390/kvm/gmap.c | 1 + arch/s390/kvm/gmap.h | 12 ++++++++++-- 3 files changed, 13 insertions(+), 3 deletions(-) diff --git a/arch/s390/kvm/dat.h b/arch/s390/kvm/dat.h index 8f8278c44879..873e13ac5a27 100644 --- a/arch/s390/kvm/dat.h +++ b/arch/s390/kvm/dat.h @@ -145,7 +145,8 @@ union pgste { unsigned long cmma_d : 1; /* Dirty flag for CMMA bits */ unsigned long prefix_notif : 1; /* Guest prefix invalidation notification */ unsigned long vsie_notif : 1; /* Referenced in a shadow table */ - unsigned long : 5; + unsigned long vsie_gmem : 1; /* Contains nested guest memory */ + unsigned long : 4; unsigned long : 8; }; struct { diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c index c1140da0689d..08fb806c9c36 100644 --- a/arch/s390/kvm/gmap.c +++ b/arch/s390/kvm/gmap.c @@ -1053,6 +1053,7 @@ int gmap_protect_rmap(struct kvm_s390_mmu_cache *mc, struct gmap *sg, gfn_t p_gf pte.h.p = 1; pgste = _gmap_ptep_xchg(sg->parent, ptep, pte, pgste, p_gfn, false); pgste.vsie_notif = 1; + pgste.vsie_gmem |= level == TABLE_TYPE_PAGE_TABLE; pgste_set_unlock(ptep, pgste); return 0; diff --git a/arch/s390/kvm/gmap.h b/arch/s390/kvm/gmap.h index 96ee1395a592..f4caa3f42c0e 100644 --- a/arch/s390/kvm/gmap.h +++ b/arch/s390/kvm/gmap.h @@ -167,6 +167,13 @@ static inline bool gmap_unmap_prefix(struct gmap *gmap, gfn_t gfn, gfn_t end) return _gmap_unmap_prefix(gmap, gfn, end, false); } +static inline bool needs_unshadow(union pte oldpte, union pte newpte, union pgste pgste) +{ + if (pgste.vsie_gmem) + return (oldpte.h.p != newpte.h.p) || newpte.h.i; + return (oldpte.h.p && !newpte.h.p) || !newpte.s.pr; +} + static inline union pgste _gmap_ptep_xchg(struct gmap *gmap, union pte *ptep, union pte newpte, union pgste pgste, gfn_t gfn, bool needs_lock) { @@ -180,8 +187,9 @@ static inline union pgste _gmap_ptep_xchg(struct gmap *gmap, union pte *ptep, un pgste.prefix_notif = 0; gmap_unmap_prefix(gmap, gfn, gfn + 1); } - if (pgste.vsie_notif && (ptep->h.p != newpte.h.p || newpte.h.i)) { + if (pgste.vsie_notif && needs_unshadow(*ptep, newpte, pgste)) { pgste.vsie_notif = 0; + pgste.vsie_gmem = 0; if (needs_lock) gmap_handle_vsie_unshadow_event(gmap, gfn); else @@ -217,7 +225,7 @@ static inline bool __must_check _gmap_crstep_xchg_atomic(struct gmap *gmap, unio gmap_unmap_prefix(gmap, gfn, gfn + align); } if (crste_leaf(oldcrste) && oldcrste.s.fc1.vsie_notif && - (newcrste.h.p || newcrste.h.i || !newcrste.s.fc1.vsie_notif)) { + ((newcrste.h.p != oldcrste.h.p) || newcrste.h.i || !newcrste.s.fc1.vsie_notif)) { newcrste.s.fc1.vsie_notif = 0; if (needs_lock) gmap_handle_vsie_unshadow_event(gmap, gfn); -- 2.54.0