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Thu, 5 Mar 2026 15:44:20 +0000 (GMT) Message-ID: Date: Thu, 5 Mar 2026 16:44:20 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/1] KVM: s390: Fix a deadlock To: Claudio Imbrenda , kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, 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 References: <20260303175206.72836-1-imbrenda@linux.ibm.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <20260303175206.72836-1-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: JL_4XwN-Td9BGXepHpvQ-iygMTDl-Tio X-Authority-Analysis: v=2.4 cv=b66/I9Gx c=1 sm=1 tr=0 ts=69a9a4d9 cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=IkcTkHD0fZMA:10 a=Yq5XynenixoA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=7qIwyxNRPOhrtI9IJb8A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMzA1MDEyNSBTYWx0ZWRfX7IODjhfoIitE S9UYrb8k6oPMXPRqrESseHbXRxEjgjNkjJQoei/wPt47Sv7KuPX+n05MofzjoUpZAYkU6XimA0s +10juapRJfnFwjIXBJnXf1rSLebcRiczHQftVTa/HQN/Lfmv+4wL5UKMvF/McS9kt+oP6yu/0VM xMz1wotmG2zUau1Ag6yTl1rMwTulOWvTtAzm5Zm5/srTvI/xKmNrAVviGNLA1JnOhtdvBtF1sks qWknLJENvQN+RPh1sQwXpHggFIo3DEk1qhS+HjHtwTFHC2iCMB+b+LzZ0HnQRr5H9OY6M217iL8 mIj1jc2s55ZgsBbTqwk9Q1+js1M4COYDcsdj2Q3QnjWXPtzO5o+e9jy6VzJVwZ2rxDZd0vcSZPn MmHQrYED1ZqqvEXKw4G4sRdEQSIzN5dy5XiKa+vYjZv5OxjnE+3AI2OFahwJGrj6apPuyyfY3u+ a/Xdty5DLi2QMEGJ0lw== X-Proofpoint-GUID: JL_4XwN-Td9BGXepHpvQ-iygMTDl-Tio 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=2026-03-05_04,2026-03-04_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 phishscore=0 clxscore=1011 adultscore=0 bulkscore=0 impostorscore=0 malwarescore=0 spamscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2602130000 definitions=main-2603050125 Am 03.03.26 um 18:52 schrieb Claudio Imbrenda: > 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") Tested-by: Christian Borntraeger I no longer see the rcu stalls. > --- > 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); >