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Mon, 26 May 2025 08:22:23 +0000 (GMT) Message-ID: <7ca1e834-a501-4c91-9458-63d5e0e2ec79@linux.ibm.com> Date: Mon, 26 May 2025 10:22:23 +0200 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/3] KVM: s390: Always allocate esca_block To: Christoph Schlameuss , kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, Christian Borntraeger , Claudio Imbrenda , David Hildenbrand , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Thomas Huth References: <20250522-rm-bsca-v3-0-51d169738fcf@linux.ibm.com> <20250522-rm-bsca-v3-2-51d169738fcf@linux.ibm.com> Content-Language: en-US From: Janosch Frank Autocrypt: addr=frankja@linux.ibm.com; keydata= xsFNBFubpD4BEADX0uhkRhkj2AVn7kI4IuPY3A8xKat0ihuPDXbynUC77mNox7yvK3X5QBO6 qLqYr+qrG3buymJJRD9xkp4mqgasHdB5WR9MhXWKH08EvtvAMkEJLnqxgbqf8td3pCQ2cEpv 15mH49iKSmlTcJ+PvJpGZcq/jE42u9/0YFHhozm8GfQdb9SOI/wBSsOqcXcLTUeAvbdqSBZe zuMRBivJQQI1esD9HuADmxdE7c4AeMlap9MvxvUtWk4ZJ/1Z3swMVCGzZb2Xg/9jZpLsyQzb lDbbTlEeyBACeED7DYLZI3d0SFKeJZ1SUyMmSOcr9zeSh4S4h4w8xgDDGmeDVygBQZa1HaoL Esb8Y4avOYIgYDhgkCh0nol7XQ5i/yKLtnNThubAcxNyryw1xSstnKlxPRoxtqTsxMAiSekk 0m3WJwvwd1s878HrQNK0orWd8BzzlSswzjNfQYLF466JOjHPWFOok9pzRs+ucrs6MUwDJj0S cITWU9Rxb04XyigY4XmZ8dywaxwi2ZVTEg+MD+sPmRrTw+5F+sU83cUstuymF3w1GmyofgsU Z+/ldjToHnq21MNa1wx0lCEipCCyE/8K9B9bg9pUwy5lfx7yORP3JuAUfCYb8DVSHWBPHKNj HTOLb2g2UT65AjZEQE95U2AY9iYm5usMqaWD39pAHfhC09/7NQARAQABzSVKYW5vc2NoIEZy YW5rIDxmcmFua2phQGxpbnV4LmlibS5jb20+wsF3BBMBCAAhBQJbm6Q+AhsjBQsJCAcCBhUI CQoLAgQWAgMBAh4BAheAAAoJEONU5rjiOLn4p9gQALjkdj5euJVI2nNT3/IAxAhQSmRhPEt0 AmnCYnuTcHRWPujNr5kqgtyER9+EMQ0ZkX44JU2q7OWxTdSNSAN/5Z7qmOR9JySvDOf4d3mS bMB5zxL9d8SbnSs1uW96H9ZBTlTQnmLfsiM9TetAjSrR8nUmjGhe2YUhJLR1v1LguME+YseT eXnLzIzqqpu311/eYiiIGcmaOjPCE+vFjcXL5oLnGUE73qSYiujwhfPCCUK0850o1fUAYq5p CNBCoKT4OddZR+0itKc/cT6NwEDwdokeg0+rAhxb4Rv5oFO70lziBplEjOxu3dqgIKbHbjza EXTb+mr7VI9O4tTdqrwJo2q9zLqqOfDBi7NDvZFLzaCewhbdEpDYVu6/WxprAY94hY3F4trT rQMHJKQENtF6ZTQc9fcT5I3gAmP+OEvDE5hcTALpWm6Z6SzxO7gEYCnF+qGXqp8sJVrweMub UscyLqHoqdZC2UG4LQ1OJ97nzDpIRe0g6oJ9ZIYHKmfw5jjwH6rASTld5MFWajWdNsqK15k/ RZnHAGICKVIBOBsq26m4EsBlfCdt3b/6emuBjUXR1pyjHMz2awWzCq6/6OWs5eANZ0sdosNq dq2v0ULYTazJz2rlCXV89qRa7ukkNwdBSZNEwsD4eEMicj1LSrqWDZMAALw50L4jxaMD7lPL jJbazsFNBFubpD4BEADAcUTRqXF/aY53OSH7IwIK9lFKxIm0IoFkOEh7LMfp7FGzaP7ANrZd cIzhZi38xyOkcaFY+npGEWvko7rlIAn0JpBO4x3hfhmhBD/WSY8LQIFQNNjEm3vzrMo7b9Jb JAqQxfbURY3Dql3GUzeWTG9uaJ00u+EEPlY8zcVShDltIl5PLih20e8xgTnNzx5c110lQSu0 iZv2lAE6DM+2bJQTsMSYiwKlwTuv9LI9Chnoo6+tsN55NqyMxYqJgElk3VzlTXSr3+rtSCwf tq2cinETbzxc1XuhIX6pu/aCGnNfuEkM34b7G1D6CPzDMqokNFbyoO6DQ1+fW6c5gctXg/lZ 602iEl4C4rgcr3+EpfoPUWzKeM8JXv5Kpq4YDxhvbitr8Dm8gr38+UKFZKlWLlwhQ56r/zAU v6LIsm11GmFs2/cmgD1bqBTNHHcTWwWtRTLgmnqJbVisMJuYJt4KNPqphTWsPY8SEtbufIlY HXOJ2lqUzOReTrie2u0qcSvGAbSfec9apTFl2Xko/ddqPcZMpKhBiXmY8tJzSPk3+G4tqur4 6TYAm5ouitJsgAR61Cu7s+PNuq/pTLDhK+6/Njmc94NGBcRA4qTuysEGE79vYWP2oIAU4Fv6 gqaWHZ4MEI2XTqH8wiwzPdCQPYsSE0fXWiYu7ObeErT6iLSTZGx4rQARAQABwsFfBBgBCAAJ BQJbm6Q+AhsMAAoJEONU5rjiOLn4DDEP/RuyckW65SZcPG4cMfNgWxZF8rVjeVl/9PBfy01K 8R0hajU40bWtXSMiby7j0/dMjz99jN6L+AJHJvrLz4qYRzn2Ys843W+RfXj62Zde4YNBE5SL jJweRCbMWKaJLj6499fctxTyeb9+AMLQS4yRSwHuAZLmAb5AyCW1gBcTWZb8ON5BmWnRqeGm IgC1EvCnHy++aBnHTn0m+zV89BhTLTUal35tcjUFwluBY39R2ux/HNlBO1GY3Z+WYXhBvq7q katThLjaQSmnOrMhzqYmdShP1leFTVbzXUUIYv/GbynO/YrL2gaQpaP1bEUEi8lUAfXJbEWG dnHFkciryi092E8/9j89DJg4mmZqOau7TtUxjRMlBcIliXkzSLUk+QvD4LK1kWievJse4mte FBdkWHfP4BH/+8DxapRcG1UAheSnSRQ5LiO50annOB7oXF+vgKIaie2TBfZxQNGAs3RQ+bga DchCqFm5adiSP5+OT4NjkKUeGpBe/aRyQSle/RropTgCi85pje/juYEn2P9UAgkfBJrOHvQ9 Z+2Sva8FRd61NJLkCJ4LFumRn9wQlX2icFbi8UDV3do0hXJRRYTWCxrHscMhkrFWLhYiPF4i phX7UNdOWBQ90qpHyAxHmDazdo27gEjfvsgYMdveKknEOTEb5phwxWgg7BcIDoJf9UMC In-Reply-To: <20250522-rm-bsca-v3-2-51d169738fcf@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=AOOMbaiN c=1 sm=1 tr=0 ts=683424c4 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=dt9VzEwgFbYA:10 a=VnNF1IyMAAAA:8 a=NnW4VVLYpB-IhxFGeE8A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: trwr057UMWK8VHx2RT2TgJMvvmSFV8ct X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTI2MDA2NyBTYWx0ZWRfX564rJ4HN5xDS Dhakl1tZ1sCLAbxDakuiPXfQMA084PpE8cWTuNjxZw/prSZvLbsTWnRSBsUVbiKsz1BDuHAqSsp gRVPymVWuVntMhuYBO30iTlZ70lT/4cD+pMGTpp2QsINrRGR4fM8eHZl//tPmxXwJBhVsIVARLR syHsKksZUnkCkiz51IeGKfsALYuTcVQb/74erzzSiCdMtfu0WLDf7KamOr3fk2BTcFDzRt11V5B SpI4aqzTSOw9NYkarAUfJIgCNCu1bFm0qxReqzN7c4J8qI7vvKIB4XttyTPvLok5g4IKOknzqpi apLxfq9+yGNtZb+Ftt0zBn0P5IYtfypOBa9XmFLL73nrz9zk9oMuys5JqCEyijRT8HfaF/ZkGsw Y2OmahK+ELzqnbWEfE8kkr0b7G6le3CVximItEJctMoe149ySLYmaxQwdgizsLgAcLXlH/u0 X-Proofpoint-GUID: trwr057UMWK8VHx2RT2TgJMvvmSFV8ct 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=2025-05-26_04,2025-05-22_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 priorityscore=1501 adultscore=0 bulkscore=0 mlxscore=0 spamscore=0 impostorscore=0 mlxlogscore=733 malwarescore=0 lowpriorityscore=0 phishscore=0 clxscore=1015 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505160000 definitions=main-2505260067 On 5/22/25 11:31 AM, Christoph Schlameuss wrote: > Instead of allocating a BSCA and upgrading it for PV or when adding the > 65th cpu we can always use the ESCA. > > The only downside of the change is that we will always allocate 4 pages > for a 248 cpu ESCA instead of a single page for the BSCA per VM. > In return we can delete a bunch of checks and special handling depending > on the SCA type as well as the whole BSCA to ESCA conversion. > > As a fallback we can still run without SCA entries when the SIGP > interpretation facility or ESCA are not available. > > Signed-off-by: Christoph Schlameuss > --- > arch/s390/include/asm/kvm_host.h | 1 - > arch/s390/kvm/interrupt.c | 71 +++++------------ > arch/s390/kvm/kvm-s390.c | 161 ++++++--------------------------------- > arch/s390/kvm/kvm-s390.h | 4 +- > 4 files changed, 45 insertions(+), 192 deletions(-) [...] > @@ -80,33 +70,17 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id) > > BUG_ON(!kvm_s390_use_sca_entries()); > read_lock(&vcpu->kvm->arch.sca_lock); > - if (vcpu->kvm->arch.use_esca) { > - 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 new_val = {0}, old_val; > - > - old_val = READ_ONCE(*sigp_ctrl); > - new_val.scn = src_id; > - new_val.c = 1; > - old_val.c = 0; > - > - expect = old_val.value; > - rc = cmpxchg(&sigp_ctrl->value, old_val.value, new_val.value); > - } else { > - struct bsca_block *sca = vcpu->kvm->arch.sca; > - union bsca_sigp_ctrl *sigp_ctrl = > - &(sca->cpu[vcpu->vcpu_id].sigp_ctrl); > - union bsca_sigp_ctrl new_val = {0}, old_val; > + 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 new_val = {0}, old_val; Since we don't have a need for inline declarations anymore, could you move those to the beginning of the function? @Christian @Claudio: Another interesting question is locking. The SCA RW lock protected against the bsca->esca switch which never happens after this patch. Can't we rip out that lock and maybe get a bit of performance and even less code? (In another patch set to limit the destructive potential)