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Tue, 23 Jun 2026 15:33:33 +0000 (GMT) Received: from p-imbrenda.ehn-de.ibm.com (unknown [9.224.75.30]) by smtpav05.fra02v.mail.ibm.com (Postfix) with ESMTP; Tue, 23 Jun 2026 15:33:33 +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, hca@linux.ibm.com, gerald.schaefer@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com Subject: [PATCH v6 10/10] KVM: s390: vsie: Avoid potential deadlock with real spaces Date: Tue, 23 Jun 2026 17:33:31 +0200 Message-ID: <20260623153331.233784-11-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260623153331.233784-1-imbrenda@linux.ibm.com> References: <20260623153331.233784-1-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-Spam-Details-Enc: AW1haW4tMjYwNjIzMDEyNiBTYWx0ZWRfXyYNt9DjY60SA 3iskX9IJE158FeM3nYxSX0jhKp0lqaSbcsu1J26q/fk8c1/oubCEGpUjO3ug4FFwE8GuPumYEir pAKcjbvBQpadzl9FTXiJ8tjSgQ7uXAUqkILUVpjtiejR/usR7LHc1YnegDrIMJXmps+HxFyhEWb G1UcdfubHYzn4CQT0JXVrNodAp0J23dQ0R9U7oGl6zlHSzHqrDqut3ggunFyR2RXTXEdmf32JZb VlAFEKt3pU1kvPIJErlK4YInGuSqrbXeoSFSvbzNySY3eB8ifQM1WrE7/zXrGd5qz8Nku1AsUur I3o/dghWmnmE6PxCcGRlRREZP4BsmzkTaNT4kPxNsopRMuUSewNyUjjCiIa6NCoiaC7nBYa2Us5 bzut8t/BEwniHcfteTL1qEaoBi+M5P8DbfvtE+Zh5yWVj0pKV0xT1sw9BKxUIq9wwjxM7XTb1Kh KVUiVTY/C4uLPoUvRYA== X-Proofpoint-GUID: jNFs-Kn4hJ58UVaWh_n2FdZFMZ_2_bdR X-Proofpoint-Spam-Info: AW1haW4tMjYwNjIzMDEyNiBTYWx0ZWRfX7mQlw9iucNjc 5Lepzkvjk08yt0PA0F2d0UY3fs6g2KWKpOW4BofIlj4VyAxsSjCETz+/Uc6CggV36/i+wluPKJO GT1oYvJfxyVK7L6vAmbGJewh+G/0J/U= X-Authority-Analysis: v=2.4 cv=I/lVgtgg c=1 sm=1 tr=0 ts=6a3aa752 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=FelO9ux0wxsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VnNF1IyMAAAA:8 a=h1X_5t0Fh-6HCxHrEOoA:9 X-Proofpoint-ORIG-GUID: jNFs-Kn4hJ58UVaWh_n2FdZFMZ_2_bdR X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-23_03,2026-06-23_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 spamscore=0 phishscore=0 clxscore=1015 priorityscore=1501 adultscore=0 impostorscore=0 bulkscore=0 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2606230126 The natural lock ordering is mmu_lock -> children_lock, but in gmap_create_shadow() the reverse order is used when handling shadowing of real address spaces. Convert the inner locking of kvm->mmu_lock to a trylock; return -EAGAIN if the lock is busy, and let the caller try again. This path is not expected to happen in real-life scenarios, so its performance is not important. Fixes: a2c17f9270cc ("KVM: s390: New gmap code") Signed-off-by: Claudio Imbrenda --- arch/s390/kvm/gmap.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/arch/s390/kvm/gmap.c b/arch/s390/kvm/gmap.c index 0f944944badf..1fc8d848b2bc 100644 --- a/arch/s390/kvm/gmap.c +++ b/arch/s390/kvm/gmap.c @@ -1349,8 +1349,12 @@ struct gmap *gmap_create_shadow(struct kvm_s390_mmu_cache *mc, struct gmap *pare /* Only allow one real-space gmap shadow. */ list_for_each_entry(sg, &parent->children, list) { if (sg->guest_asce.r) { - scoped_guard(write_lock, &parent->kvm->mmu_lock) + if (write_trylock(&parent->kvm->mmu_lock)) { gmap_unshadow(sg); + write_unlock(&parent->kvm->mmu_lock); + } else { + return ERR_PTR(-EAGAIN); + } break; } } -- 2.54.0