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Wed, 22 Jul 2026 17:06:24 +0000 (GMT) Received: from IBM-D32RQW3.ibm.com (unknown [9.61.253.249]) by smtpav05.wdc07v.mail.ibm.com (Postfix) with ESMTP; Wed, 22 Jul 2026 17:06:24 +0000 (GMT) From: Farhan Ali To: linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, kvm@vger.kernel.org Cc: alifm@linux.ibm.com, mjrosato@linux.ibm.com, borntraeger@linux.ibm.com, farman@linux.ibm.com Subject: [PATCH v4 2/6] KVM: s390: pci: Fix memory accounting for pinned/unpinned pages Date: Wed, 22 Jul 2026 10:06:17 -0700 Message-ID: <20260722170621.1686-3-alifm@linux.ibm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260722170621.1686-1-alifm@linux.ibm.com> References: <20260722170621.1686-1-alifm@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzIyMDE2NCBTYWx0ZWRfX0IqjqaNOqwCR l909dxNIsyefqCqrg/2+AQybJBoF5y4mT487v82ZdkD4rUfBb/EctMc5BAfRTW2peUgCFXcXlmt y7yKQ8BcudjjaWb0IP7+krKUSc9AaTRJR/ozOeK3hjvcuHeicT/SpHvTo8uLg/hO672j73JEAYy ipwvZ/p7z7YLAseRblnme2aUesDkgridK9v5Jhip00soRXEFCQ9UKATVqMZrs39BAh7YX/ocViM miYJB9qWgsvhaFcIUAua5BHPQomsPjrzKeWgcNuLAmjC9grJiF9fUEBYJjaOUng0ByvK0Zo9xzh Q8AgBHWTl1BVLAXq8SQumj1i6lzF5u4fVik1zoC3vSE8GubeObCwbmuZDuAga/A8rn0/MahRMDC 22JA9TXozUXkwzNS/dLgx89uwO84L+Y2eNSaGIXDDRDacw9707yA1+pPzUMCFaRu3D1nL4qH4Ni nUSULgPpYvUEEwmdgFA== X-Proofpoint-GUID: aVjV73MfRRw9BttxKkDzx7CfcvS3lxqB X-Authority-Analysis: v=2.4 cv=MelcfZ/f c=1 sm=1 tr=0 ts=6a60f893 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=RAioF0-LDSMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VnNF1IyMAAAA:8 a=EQJuD_CdQHuXhf-s-5YA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYwNzIyMDE2NCBTYWx0ZWRfX7sZQd7STQOy9 kPg+8RQdSqpWGEtiTxd14Wluns6LNIq7rfQHxKYBCGrVv79gxD+Yu3Zdi1tkB09M8aZAgQt111m KwJQ9sVltfsfNsMTQYb+kZ+oRTLF7vg= X-Proofpoint-ORIG-GUID: aVjV73MfRRw9BttxKkDzx7CfcvS3lxqB X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-22_04,2026-07-22_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 lowpriorityscore=0 priorityscore=1501 bulkscore=0 spamscore=0 clxscore=1015 malwarescore=0 phishscore=0 adultscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607220164 The account_mem() and unaccount_mem() functions call get_uid() which increments the reference count of struct user_struct on every invocation. But we don't decrement the count by calling free_uid(). It also accounted/unaccounted the pages against the current->mm. But its possible the unaccount_mem() can be called from a different process context than the one that originally pinned the pages. Let's fix this by storing the pinning process user_struct and mm_struct when accounting for pinned pages, and subsequently free these resources when the pages are unpinned. Fixes: 3c5a1b6f0a18 ("KVM: s390: pci: provide routines for enabling/disabling interrupt forwarding") Signed-off-by: Farhan Ali --- arch/s390/kvm/pci.c | 38 ++++++++++++++++++++++++++++---------- arch/s390/kvm/pci.h | 2 ++ 2 files changed, 30 insertions(+), 10 deletions(-) diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c index d2a11cdf6941..1b3114c7cfbb 100644 --- a/arch/s390/kvm/pci.c +++ b/arch/s390/kvm/pci.c @@ -190,33 +190,51 @@ static int kvm_zpci_clear_airq(struct zpci_dev *zdev) return cc ? -EIO : 0; } -static inline void unaccount_mem(unsigned long nr_pages) +static inline void unaccount_mem(struct kvm_zdev *kzdev, unsigned long nr_pages) { - struct user_struct *user = get_uid(current_user()); + struct user_struct *user = kzdev->user_account; + struct mm_struct *mm_account = kzdev->mm_account; - if (user) + if (user) { atomic_long_sub(nr_pages, &user->locked_vm); - if (current->mm) - atomic64_sub(nr_pages, ¤t->mm->pinned_vm); + free_uid(user); + kzdev->user_account = NULL; + } + + if (mm_account) { + atomic64_sub(nr_pages, &mm_account->pinned_vm); + mmdrop(mm_account); + kzdev->mm_account = NULL; + } } -static inline int account_mem(unsigned long nr_pages) +static inline int account_mem(struct kvm_zdev *kzdev, unsigned long nr_pages) { struct user_struct *user = get_uid(current_user()); unsigned long page_limit, cur_pages, new_pages; + int rc = 0; page_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; cur_pages = atomic_long_read(&user->locked_vm); do { new_pages = cur_pages + nr_pages; - if (new_pages > page_limit) - return -ENOMEM; + if (new_pages > page_limit) { + rc = -ENOMEM; + goto out; + } } while (!atomic_long_try_cmpxchg(&user->locked_vm, &cur_pages, new_pages)); + mmgrab(current->mm); atomic64_add(nr_pages, ¤t->mm->pinned_vm); + kzdev->user_account = user; + kzdev->mm_account = current->mm; return 0; + +out: + free_uid(user); + return rc; } static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib, @@ -279,7 +297,7 @@ static int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib, } /* Account for pinned pages, roll back on failure */ - if (account_mem(pcount)) + if (account_mem(zdev->kzdev, pcount)) goto unpin2; /* AISB must be allocated before we can fill in GAITE */ @@ -400,7 +418,7 @@ static int kvm_s390_pci_aif_disable(struct zpci_dev *zdev, bool force) pcount++; } if (pcount > 0) - unaccount_mem(pcount); + unaccount_mem(kzdev, pcount); out: mutex_unlock(&aift->aift_lock); diff --git a/arch/s390/kvm/pci.h b/arch/s390/kvm/pci.h index ff0972dd5e71..544e6aa75e38 100644 --- a/arch/s390/kvm/pci.h +++ b/arch/s390/kvm/pci.h @@ -21,6 +21,8 @@ struct kvm_zdev { struct zpci_dev *zdev; struct kvm *kvm; struct zpci_fib fib; + struct user_struct *user_account; + struct mm_struct *mm_account; struct list_head entry; }; -- 2.43.0