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Tue, 3 Mar 2026 17:52:07 +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, nsg@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 v1 1/1] KVM: s390: Fix a deadlock Date: Tue, 3 Mar 2026 18:52:06 +0100 Message-ID: <20260303175206.72836-1-imbrenda@linux.ibm.com> X-Mailer: git-send-email 2.53.0 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: PBaeN14LYjKSxauLQKyTTvM25MO5KtkK X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzAzMDE0MiBTYWx0ZWRfX6PVdHQ/fKf6i +VrcThqcPj2FID06dYjp6i5kOoqSt/JpQaFFiMCO3LCNmvrjOiruC4YC/bwxKQ5lE71Uxmr3jJT 4PUJoKufz8VezXo5mATDmu1KoZWVKi8dXFe9grP6GVOm/UV3dVCAs+mQP/gdjBup+W/HLrBbKUU soe7bAnRbx0TkS0kn040UOiAFdLdlxN5tJi/uwBYZegENRsn7kit6kfAS2x/gRcJfsBERKlPEmY I8LD8sQVeSRCijlVhJizszjRJgdJmoi0dA5VMXn++J3KE5ktneSS/Ab9DmVWqErS13iVeUErHcv aVuHPwY8ayVbN6lPS+C9+fPuovEAySYSk2TPvjNg2QrdjzO5Spxx4+5a0G2XJo4FmPqioxzKHiq 6Iu4U3p+UftTxQdBuJkKXH+n/oRJAodIdyx2Invjm87CYoqq1Wj+Tyuxde81CV2wAKbn1xb3uSZ PbHn47iPcEE1oDXbiSQ== X-Authority-Analysis: v=2.4 cv=H7DWAuYi c=1 sm=1 tr=0 ts=69a71fcd cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=MFxHPMzSBJxkdh7CuRcA:9 X-Proofpoint-ORIG-GUID: PBaeN14LYjKSxauLQKyTTvM25MO5KtkK X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-03-03_02,2026-03-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 suspectscore=0 phishscore=0 clxscore=1015 priorityscore=1501 adultscore=0 bulkscore=0 spamscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603030142 In some scenarios, a deadlock can happen, involving _do_shadow_pte(). Convert all usages of pgste_get_lock() to pgste_get_trylock() in _do_shadow_pte() and return -EAGAIN. All callers can already deal with -EAGAIN being returned. Signed-off-by: Claudio Imbrenda Fixes: e38c884df921 ("KVM: s390: Switch to new gmap") --- arch/s390/kvm/gaccess.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c index 4630b2a067ea..a9da9390867d 100644 --- a/arch/s390/kvm/gaccess.c +++ b/arch/s390/kvm/gaccess.c @@ -1434,7 +1434,8 @@ static int _do_shadow_pte(struct gmap *sg, gpa_t raddr, union pte *ptep_h, union if (rc) return rc; - pgste = pgste_get_lock(ptep_h); + if (!pgste_get_trylock(ptep_h, &pgste)) + return -EAGAIN; newpte = _pte(f->pfn, f->writable, !p, 0); newpte.s.d |= ptep->s.d; newpte.s.sd |= ptep->s.sd; @@ -1444,7 +1445,8 @@ static int _do_shadow_pte(struct gmap *sg, gpa_t raddr, union pte *ptep_h, union pgste_set_unlock(ptep_h, pgste); newpte = _pte(f->pfn, 0, !p, 0); - pgste = pgste_get_lock(ptep); + if (!pgste_get_trylock(ptep, &pgste)) + return -EAGAIN; pgste = __dat_ptep_xchg(ptep, pgste, newpte, gpa_to_gfn(raddr), sg->asce, uses_skeys(sg)); pgste_set_unlock(ptep, pgste); -- 2.53.0