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Tue, 11 Aug 2026 20:43:59 +0000 (GMT) Received: from [9.61.146.44] (unknown [9.61.146.44]) by smtpav03.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 11 Aug 2026 20:43:59 +0000 (GMT) Message-ID: Date: Tue, 11 Aug 2026 16:43:59 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 8/8] s390/vfio-ap: Fix hot-unplug skipped when last AP adapter or domain removed To: Anthony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: jjherne@linux.ibm.com, borntraeger@de.ibm.com, pasic@linux.ibm.com, alex@shazbot.org, kwankhede@nvidia.com, fiuczy@linux.ibm.com, pbonzini@redhat.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, agordeev@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, stable@vger.kernel.org References: <20260810192257.1208410-1-akrowiak@linux.ibm.com> <20260810192257.1208410-9-akrowiak@linux.ibm.com> From: Matthew Rosato Content-Language: en-US In-Reply-To: <20260810192257.1208410-9-akrowiak@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODExMDE3MyBTYWx0ZWRfX1xvESTZERLux DfbFnChO2Vrxi7v5fGkLRJ55hXCqSV+gTbWnBHdu9X0RRkBRPjES+LCUlQ3JVOYQSDAGg6z6EVE Q/iQCV2vfL7sfbngwTH1qhhAYr1zJV/y7iZpzD2VpPkDMJhez/AjrtefFXQBejsUI91jVtGWECC pSb54FCuCLsmNApYSA9ptPPt/7w7nWO2/9qiUx6Mzey3IE/uyw5a63+ygt42hzUhsr3PfKdvoAg /olUjXERgeu69UrtXjPuE6M1bDoyoVeSXv05UUEAqIzEC3gfkU4AqfiNx4Zwlf6zmqQ3dz7jxYB L0af0xcmovNvcwMHdOfEQ7rEPYKqlx/5djm/q4c35azZCc7GCbryby1hDroo0lOGomaaTFGvyBm 46CFOBTb3ck9nobM4ZbTeItWOylpLDj0eU9bs/X1pl4v2Vi3jur3Fbdr4tf3di2I9o8lPjmfX+H q+gns3Oe0Djqd7tCNzw== X-Proofpoint-ORIG-GUID: x7Yg1-cmNCD_Aqgj5fSNTTgz2mGNnovQ X-Proofpoint-Spam-Info: AW1haW4tMjYwODExMDE3MyBTYWx0ZWRfXyzxgW6RpydYG xKvCIrEbPqiRLMsdxDtwU+ujHsYW0appC5BqQawtiTwn+FSjRtrmn3EwUBCETLET+5l2IpxocyA s51B5yShKFipMmsaLPWpUq7czviL6HU= X-Authority-Analysis: v=2.4 cv=IfK3n2qa c=1 sm=1 tr=0 ts=6a7b8993 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=fD2uEicUE52K2J2evs0A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: x7Yg1-cmNCD_Aqgj5fSNTTgz2mGNnovQ 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=2026-08-11_05,2026-08-10_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 priorityscore=1501 impostorscore=0 bulkscore=0 clxscore=1015 lowpriorityscore=0 adultscore=0 malwarescore=0 spamscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608110173 On 8/10/26 3:22 PM, Anthony Krowiak wrote: > The vfio_ap_mdev_hot_unplug_cfg() function uses the return value of > bitmap_andnot() to determine whether the guest APCB needs to be updated. > However, bitmap_andnot() returns false when the resulting destination > bitmap is empty. This means that if the only adapter, domain or control > domain assigned to an mdev is removed from the host's AP confikguration, s/confikguration/configuration/ > the bit is correctly cleared from the shadow APCB, but bitmap_andnot() > returns false because the result is an empty bitmap. Consequently, > do_hotplug remains 0 and vfio_ap_mdev_update_guest_apcb() is never called, > leaving the KVM guest with stale hardware access to the unplugged AP > devices. > > Fix this by replacing the bitmap_andnot() return value check with > bitmap_intersects() to determine whether the shadow APCB actually > overlaps with the removal mask. If there is an intersection, call > bitmap_andnot() solely for its side effect of clearing the bits, then > unconditionally set do_hotplug to trigger the guest APCB update. > > Fixes: eeb386aeb5b7c ("s390/vfio-ap: handle config changed and scan complete notification") > Cc: stable@vger.kernel.org > Signed-off-by: Anthony Krowiak Reviewed-by: Matthew Rosato Also please look at the one other pre-existing finding against this patch, another potential follow-on.