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Fri, 14 Aug 2026 16:33:56 +0000 (GMT) Received: from p-imbrenda.ehn-de.ibm.com (unknown [9.224.75.30]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Fri, 14 Aug 2026 16:33:56 +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 v2 2/6] KVM: s390: Fix _gaccess_shadow_fault() Date: Fri, 14 Aug 2026 18:33:51 +0200 Message-ID: <20260814163355.227191-3-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260814163355.227191-1-imbrenda@linux.ibm.com> References: <20260814163355.227191-1-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: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 3kb41jCXGi5Xc2IktiwA3mQktdkzYxX6 X-Authority-Analysis: v=2.4 cv=PbDPQChd c=1 sm=1 tr=0 ts=6a7f437b cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=iQ6ETzBq9ecOQQE5vZCe:22 a=VnNF1IyMAAAA:8 a=nPGPQeRDbKebYXXOS2MA:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODE0MDEyNiBTYWx0ZWRfX/u+8dMJmrZ2T BgcPpHaO1Ha00vcH7NOtlIlOE4ifCf8ePvji2BNH3sfNC5jAqF/MNMCnzIN1aUbdEvg8UU22yn9 uV7ajxPGNBpUl2CLAiJj5qkMqwhkPkRxSWdNxLGZA6fJRZCv7kQdVDxjzlnMiwW6opiqSuLEd0w 09OOAXztnibtakvmCEpfb/9NRvUuc7V6rX/diTWfAX+92t6hGzo+QfXNlEGtZ9PqdqaYbAJ8tcA NhktLybZUkipPKCm5XwAtr4yA6KWRgoNM44nRtNhSJ8Ay/APvzQrnT2cuxok2o88KjAcrNM/XR1 TllU7CEIGzBw2gGU1C2rUC3XAZqjXHDlRCjDN2nOrWKEeObT6xOJXBM4vqiv9PodJzYYbNRrcaN NE3pllyRV3pSl9gSWcpkGgZFl9jebqgcqto73+12YSU6srC0N6oY5fJnAHaPV/2De/+DDBhzeBp 01yDlAlhsl6AIythM1A== X-Proofpoint-ORIG-GUID: 3kb41jCXGi5Xc2IktiwA3mQktdkzYxX6 X-Proofpoint-Spam-Info: AW1haW4tMjYwODE0MDEyNiBTYWx0ZWRfX/9nxsXAVR+z4 9wsUGIgXS99Msha/FhUZxaWmBWg8atIBVs8n7FqK0Fi4qBMTxUhDob1AvHfAWlRMKZ/2rCmKt2R xp+xjZ4CmyrsohN0IP7XwNvhkj2kihQ= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-14_05,2026-08-12_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 bulkscore=0 impostorscore=0 malwarescore=0 adultscore=0 clxscore=1015 priorityscore=1501 suspectscore=0 phishscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608140126 In some circumstances, it is possible that the page of nested guest memory that is being shadowed is not present at all in the parent guest gmap. dat_entry_walk() will not find any leaf entry and return with -ENOENT, which will erroneously be propagated all the way to userspace. Fix by manually calling gmap_link() on the memory of the nested guest that is being shadowed if the mapping was not already present. Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/gaccess.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index 36102b2727fb..7c1f614ec314 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -1593,12 +1593,25 @@ static inline int ___gaccess_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg parent = READ_ONCE(sg->parent); if (!parent) return -EAGAIN; +retry: scoped_guard(spinlock, &parent->children_lock) { if (READ_ONCE(sg->parent) != parent) return -EAGAIN; sg->invalidated = false; rc = _gaccess_do_shadow(vcpu->arch.mc, sg, saddr, walk); } + if (rc == -ENOENT) { + struct kvm_memory_slot *slot; + struct guest_fault *entries; + + entries = get_entries(walk); + slot = kvm_vcpu_gfn_to_memslot(vcpu, entries[LEVEL_MEM].gfn); + if (!slot) + return PGM_ADDRESSING; + rc = gmap_link(vcpu->arch.mc, parent, entries + LEVEL_MEM, slot); + if (!rc) + goto retry; + } if (!rc) kvm_s390_release_faultin_array(vcpu->kvm, walk->raw_entries, false); return rc; -- 2.55.0