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Mon, 25 Nov 2024 13:37:57 +0000 (GMT) Date: Mon, 25 Nov 2024 14:37:55 +0100 From: Heiko Carstens To: Claudio Imbrenda Cc: Christian Borntraeger , Janosch Frank , David Hildenbrand , kvm@vger.kernel.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] KVM: s390: Remove one byte cmpxchg() usage Message-ID: <20241125133755.14417-D-hca@linux.ibm.com> References: <20241125115039.1809353-1-hca@linux.ibm.com> <20241125115039.1809353-3-hca@linux.ibm.com> <20241125131617.13be742d@p-imbrenda> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20241125131617.13be742d@p-imbrenda> X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: sgq_zrl2iWWgqKfKqzJZimk0kaIAOyH- X-Proofpoint-GUID: sgq_zrl2iWWgqKfKqzJZimk0kaIAOyH- X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.62.30 definitions=2024-10-15_01,2024-10-11_01,2024-09-30_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 malwarescore=0 mlxlogscore=851 spamscore=0 suspectscore=0 phishscore=0 clxscore=1015 mlxscore=0 lowpriorityscore=0 impostorscore=0 adultscore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2409260000 definitions=main-2411250115 On Mon, Nov 25, 2024 at 01:16:17PM +0100, Claudio Imbrenda wrote: > On Mon, 25 Nov 2024 12:50:38 +0100 > Heiko Carstens wrote: > > @@ -128,23 +126,16 @@ static void sca_clear_ext_call(struct kvm_vcpu *vcpu) > > struct esca_block *sca = vcpu->kvm->arch.sca; > > union esca_sigp_ctrl *sigp_ctrl = > > &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); > > - union esca_sigp_ctrl old; > > > > - old = READ_ONCE(*sigp_ctrl); > > - expect = old.value; > > - rc = cmpxchg(&sigp_ctrl->value, old.value, 0); > > + WRITE_ONCE(sigp_ctrl->value, 9); > > that's supposed to be a 0, right? Duh... yes, of course. I added the "9" to better find the corresponding code in assembly, and obviously forgot to replace it with 0 again. Thanks for pointing this out! Strange enough this still worked. Hmm.