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(was Re: [PATCH 00/14] KVM: Halt-polling fixes, cleanups and a new stat) To: Sean Christopherson , Paolo Bonzini , David Matlack , Jon Cargille , Jim Mattson Cc: James Morse , Alexandru Elisei , Suzuki K Poulose , David Hildenbrand , Cornelia Huck , Claudio Imbrenda , Vitaly Kuznetsov , Wanpeng Li , Joerg Roedel , linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, linux-mips@vger.kernel.org, kvm@vger.kernel.org, kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, Jing Zhang , Marc Zyngier , Huacai Chen , Aleksandar Markovic , Paul Mackerras , Janosch Frank References: <20210925005528.1145584-1-seanjc@google.com> From: Christian Borntraeger Message-ID: <03f2f5ab-e809-2ba5-bd98-3393c3b843d2@de.ibm.com> Date: Mon, 27 Sep 2021 09:22:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210925005528.1145584-1-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: YhudcLNxmoRTm9--b5hlc8B3xu2hjRt_ X-Proofpoint-GUID: AXC2xKJr4IU02TPnWWKjhfFDtMWQ5xNx X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.182.1,Aquarius:18.0.790,Hydra:6.0.391,FMLib:17.0.607.475 definitions=2021-09-27_01,2021-09-24_02,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 priorityscore=1501 mlxscore=0 phishscore=0 mlxlogscore=974 lowpriorityscore=0 impostorscore=0 adultscore=0 clxscore=1015 suspectscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2109230001 definitions=main-2109270046 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org While looking into this series, I realized that Davids patch commit acd05785e48c01edb2c4f4d014d28478b5f19fb5 Author: David Matlack AuthorDate: Fri Apr 17 15:14:46 2020 -0700 Commit: Paolo Bonzini CommitDate: Fri Apr 24 12:53:17 2020 -0400 kvm: add capability for halt polling broke the possibility for an admin to disable halt polling for already running KVM guests. In past times doing echo 0 > /sys/module/kvm/parameters/halt_poll_ns stopped polling system wide. Now all KVM guests will use the halt_poll_ns value that was active during startup - even those that do not use KVM_CAP_HALT_POLL. I guess this was not intended?