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Thu, 15 May 2025 11:26:46 +0000 (GMT) Date: Thu, 15 May 2025 13:26:34 +0200 From: Claudio Imbrenda To: Christoph Schlameuss Cc: kvm@vger.kernel.org, Christian Borntraeger , Janosch Frank , David Hildenbrand , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , linux-s390@vger.kernel.org Subject: Re: [PATCH 0/3] KVM: s390: Use ESCA instead of BSCA at VM init Message-ID: <20250515132634.5965f2df@p-imbrenda> In-Reply-To: <20250514-rm-bsca-v1-0-6c2b065a8680@linux.ibm.com> References: <20250514-rm-bsca-v1-0-6c2b065a8680@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.3.1 (GTK 3.24.49; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: KCexytTHxVa3j9rZ6Ip980lkHMyqTip0 X-Authority-Analysis: v=2.4 cv=ecg9f6EH c=1 sm=1 tr=0 ts=6825cf7b cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=kj9zAlcOel0A:10 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=XdaNJP3T_A1EuQW8jZgA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: KCexytTHxVa3j9rZ6Ip980lkHMyqTip0 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTE1MDEwOSBTYWx0ZWRfX3VHQALQnJcqv iGtE5Po8/rHTYanUcCbO3931k0gRkMnWkEvV7/Q2J0iAXPSTCZ+NnZ1nZrKn5nsAUFElzW81vho qHo4uOPL3Xq00kz1thS/pneuE3kc7QMPwyoNIHduh6YwRcM/jIpUzdK+5QjlwM7yf5T9hSPn2Sy Mx0oO7rbTVInEOq1tFEd2RRJJadahR8OJZbNZFAPV+57N5EACnxyWidoWGrXhPZ0H/uW/gdzel7 p8NnD0btR/iU8TUqaZw7W8zrBEtltOZL7Et632aPKu5Bxg+mh6pVmATepVVYLvZzJSV3yLzWaCR 1Unt7Yq/NaPsmm/626H0Pa1cB2YpGoAlukEv/iWwPwLyIhLNTHgfHjCCb2eWSs1pb4bOldwMNlq AnxzmG3eDeC3RiocFq3Q32Hgx+PM9wbBASD+2wO0GnBYmPTlSfgQwDdWlJBc9TfuB1JD2xRE X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-15_05,2025-05-14_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=532 impostorscore=0 spamscore=0 clxscore=1015 malwarescore=0 mlxscore=0 lowpriorityscore=0 priorityscore=1501 adultscore=0 bulkscore=0 suspectscore=0 phishscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505070000 definitions=main-2505150109 On Wed, 14 May 2025 18:34:48 +0200 Christoph Schlameuss wrote: > All modern IBM Z and Linux One machines do offer support for the > Extended System Control Area (ESCA). The ESCA is available since the > z114/z196 released in 2010. > KVM needs to allocate and manage the SCA for guest VMs. Prior to this > change the SCA was setup as Basic SCA only supporting a maximum of 64 > vCPUs when initializing the VM. With addition of the 65th vCPU the SCA > was needed to be converted to a ESCA. > > Instead we will now allocate the ESCA directly upon VM creation > simplifying the code in multiple places as well as completely removing > the need to convert an existing SCA. > > In cases where the ESCA is not supported (z10 and earlier) the use of > the SCA entries and with that SIGP interpretation are disabled for VMs. > This increases the number of exits from the VM in multiprocessor > scenarios and thus decreases performance. > > Signed-off-by: Christoph Schlameuss > --- > Christoph Schlameuss (3): > KVM: s390: Set KVM_MAX_VCPUS to 256 > KVM: s390: Always allocate esca_block > KVM: s390: Specify kvm->arch.sca as esca_block > > arch/s390/include/asm/kvm_host.h | 7 +- > arch/s390/include/asm/kvm_host_types.h | 2 + > arch/s390/kvm/gaccess.c | 10 +- > arch/s390/kvm/interrupt.c | 74 +++++---------- > arch/s390/kvm/kvm-s390.c | 161 ++++++--------------------------- > arch/s390/kvm/kvm-s390.h | 9 +- > 6 files changed, 57 insertions(+), 206 deletions(-) I really like that you are removing more lines than you are adding :) > --- > base-commit: 82f2b0b97b36ee3fcddf0f0780a9a0825d52fec3 > change-id: 20250513-rm-bsca-ab1e8649aca7 > > Best regards,