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Mon, 3 Aug 2026 14:50:30 +0000 (GMT) Message-ID: <8209fdba-9947-42e2-b124-81adf3419f15@linux.ibm.com> Date: Mon, 3 Aug 2026 16:50:30 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 05/13] KVM: s390: ucontrol: Fix sca_clear_ext_call() To: Claudio Imbrenda , linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, borntraeger@de.ibm.com, david@kernel.org, seiden@linux.ibm.com, nrb@linux.ibm.com, schlameuss@linux.ibm.com, gra@linux.ibm.com References: <20260803124040.126471-1-imbrenda@linux.ibm.com> <20260803124040.126471-6-imbrenda@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: <20260803124040.126471-6-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Info: AW1haW4tMjYwODAzMDEzMyBTYWx0ZWRfX1f62FE0C8eB6 SKbD7sI9rGOe3wuhhRrWPrFIBiaH7agCaI1Qa4IrNEsKs+/qeP88QTv677Yb/gIWfGwjhIE7rdr 7Dn5/4ioE37IN/gNTnGabf0I7EKXIg8= X-Authority-Analysis: v=2.4 cv=I7VVgtgg c=1 sm=1 tr=0 ts=6a70aabe cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VnNF1IyMAAAA:8 a=pRtseFs1avcj8GDnxtYA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODAzMDEzMyBTYWx0ZWRfXwpTCdWz/QKz8 wtCYylpL9onVlt4LBghkn11pgICfwTrUtlp02MPYL8MXPojDolA3TbF+2D0yfRzrtYRNrwMCeVa vsZUMkz69yJip39aC1p5VxOrRtNv+85K5xl0zXq+inkkkRyDLPspZcWoulceGCTtPHQw7FCr3GT xTfakclMQdnSzoHiBQ/VTZUZ1ZUeT67n+WtE9VHCs87b/89poPt3ckviczyow60DSPxeb4VJKcx xPlSDdtYwNBc9leSXdAlJ78wVcM5lCaXu9hIeKl0a+1+Iktc4PPIOeHqVlOSuYypwrBlAQav/L3 S7TSTDNLuayZB4Xy89OXQqL3GquxzUp6+icMd5zjOwjDn6VKYvtPp0MofSls3U4csouYuHqlXUY XsUF5KpK6nNk+D61iKuGXvVR2I3qrb2ZeoKi/0e4fAzWIkbRccQYMTpiAqd+aPmOxSLvaPlwoLv caHEXYrbzxYceDxnYWw== X-Proofpoint-ORIG-GUID: DvgCWMViXtaWT-5cuC8Y6zPltZe_nfio X-Proofpoint-GUID: DvgCWMViXtaWT-5cuC8Y6zPltZe_nfio X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-03_03,2026-08-03_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 impostorscore=0 clxscore=1015 priorityscore=1501 suspectscore=0 malwarescore=0 adultscore=0 lowpriorityscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608030133 On 8/3/26 14:40, Claudio Imbrenda wrote: > When cleaning up a UCONTROL VM, sca_clear_ext_call() will touch memory > outside of the allocated ESCA block, and UCONTROL VMs don't even use > ESCA. > > Fix by not touching ESCA for UCONTROL VMs, and fence the > KVM_S390_INTERRUPT ioctl altogether. Add extra checks in > sca_ext_call_pending() and sca_inject_ext_call() to make sure UCONTROL > VMs won't touch ESCA. > > Fencing does not cause regressions with userspace, since UCONTROL VMs > never used KVM_S390_INTERRUPT ioctls. > > Signed-off-by: Claudio Imbrenda > Fixes: 7d43bafcff17 ("KVM: s390: Make provisions for ESCA utilization") > --- > arch/s390/kvm/interrupt.c | 19 ++++++++++++++----- > arch/s390/kvm/kvm-s390.c | 5 +++++ > 2 files changed, 19 insertions(+), 5 deletions(-) > > diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c > index 2acdff130fa6..6b3f97a7513b 100644 > --- a/arch/s390/kvm/interrupt.c > +++ b/arch/s390/kvm/interrupt.c > @@ -45,13 +45,16 @@ static struct kvm_s390_gib *gib; > static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id) > { > 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 sigp_ctrl; > > if (!kvm_s390_test_cpuflags(vcpu, CPUSTAT_ECALL_PEND)) > return 0; > + if (kvm_is_ucontrol(vcpu->kvm)) > + return 0; > > BUG_ON(!kvm_s390_use_sca_entries()); > > + sigp_ctrl = sca->cpu[vcpu->vcpu_id].sigp_ctrl; > if (src_id) > *src_id = sigp_ctrl.scn; > > @@ -60,13 +63,16 @@ static int sca_ext_call_pending(struct kvm_vcpu *vcpu, int *src_id) > > static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id) > { > - 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_val, new_val = {.scn = src_id, .c = 1}; > + struct esca_block *sca = vcpu->kvm->arch.sca; > + union esca_sigp_ctrl *sigp_ctrl; > int expect, rc; > > BUG_ON(!kvm_s390_use_sca_entries()); > + if (kvm_is_ucontrol(vcpu->kvm)) > + return -EINVAL; > > + sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl; > old_val = READ_ONCE(*sigp_ctrl); > old_val.c = 0; > > @@ -84,10 +90,13 @@ static int sca_inject_ext_call(struct kvm_vcpu *vcpu, int src_id) > 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 *sigp_ctrl; > > - if (!kvm_s390_use_sca_entries() || !vcpu->arch.initialized) > + if (!kvm_s390_use_sca_entries() || !vcpu->arch.initialized || kvm_is_ucontrol(vcpu->kvm)) > return; > + > + /* Initialize after the above check, to prevent going out of bounds */ > + sigp_ctrl = &sca->cpu[vcpu->vcpu_id].sigp_ctrl; Not sure why you only add this here and not at the other two occurences. But I don't think we need these comments at all. Dereferencing things before a check is not a great idea in most cases. Especially if the check validates if the memory has been set up at all :) > kvm_s390_clear_cpuflags(vcpu, CPUSTAT_ECALL_PEND); > > WRITE_ONCE(sigp_ctrl->value, 0); > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index 5b2727d7dfd1..21574f57be72 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -2934,6 +2934,9 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) > case KVM_S390_INTERRUPT: { > struct kvm_s390_interrupt s390int; > > + r = -EINVAL; > + if (kvm_is_ucontrol(kvm)) > + break; > r = -EFAULT; > if (copy_from_user(&s390int, argp, sizeof(s390int))) > break; > @@ -5456,6 +5459,8 @@ long kvm_arch_vcpu_unlocked_ioctl(struct file *filp, unsigned int ioctl, > struct kvm_s390_interrupt s390int; > struct kvm_s390_irq s390irq = {}; > > + if (kvm_is_ucontrol(vcpu->kvm)) > + return -EINVAL; > if (copy_from_user(&s390int, argp, sizeof(s390int))) > return -EFAULT; > if (s390int_to_s390irq(&s390int, &s390irq)) Do we need changes to the api documentation for this rc?