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Thu, 1 Oct 2026 10:02:16 +0000 (GMT) Received: from li-fbf77acc-29ba-11b2-a85c-e8e934f50a46.bl1-in.ibm.com (unknown [9.123.6.5]) by smtpav07.fra02v.mail.ibm.com (Postfix) with ESMTP; Thu, 1 Oct 2026 10:02:16 +0000 (GMT) From: Gautam Menghani To: maddy@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au, chleroy@kernel.org, ritesh.list@gmail.com, sshegde@linux.ibm.com, amachhiw@linux.ibm.com, harshpb@linux.ibm.com Cc: linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH 1/3] KVM: PPC: Book3S HV: Ensure that calls to idr_alloc are synchronized Date: Thu, 1 Oct 2026 15:32:04 +0530 Message-ID: <20261001100208.1271628-2-gautam@linux.ibm.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20261001100208.1271628-1-gautam@linux.ibm.com> References: <20261001100208.1271628-1-gautam@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Proofpoint-ORIG-GUID: GliQW2aLIPp72OGWWIMIAvPkmGC8nqCJ X-Proofpoint-GUID: LuojzUTQv-XOlOmm53gahgLiY_GBx_KU X-Proofpoint-Spam-Info: AW1haW4tMjYxMDAxMDAzOCBTYWx0ZWRfX316ZXoq80y45 7HlkrTAHvaTyEulqLxLuDM53AziCgm41ccUTUhDb/eiTHQJioMc/D/ZES4bF0jzGiR7J/gELcN/ fsg/lI7qQ/uRsIq9w38Q/nWPludHVRk= X-Authority-Analysis: v=2.4 cv=Vv62kO2n c=1 sm=1 tr=0 ts=6abe2faf cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=pGLkceISAAAA:8 a=VnNF1IyMAAAA:8 a=6c1f-Q0peJaRmYMZMr8A:9 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDAxMDAzOCBTYWx0ZWRfX4saDOvOmD/ME rndDVwXEVtV8/m+Dex5mzLvOUk8qPjfS3r20WxZvS3g8kRqIaSF9Gs7LmtQujILbXnBgYujxGVU wtJwMmkcJaPBqw44AlBejEi0vhVy63BcTyMNMG8hRJ1dhwql/xU8WM0j52YnbWaD6sHfGGBET8O mFk80IrqxJT59JhZwS0b6m/azK1FvcT+fx5wvjzl/qGl+I0DcBv5G2l4B+o4fpn2UKMpCChpF0s I3QUnPWKJDTj1QJm13YIJ87sjQqLneVpUD6nqd8FHhdLeTwtoXEgwW0dL8D6kXjlkzLMr9IX+Pd 3T4s6RGsKPS43VXEQPnt3qTdBBfa29aa1uvFA8rsyoT4G4CjfLAx/NDyckuk86kHc6QTcB36qEh SlUfSgTDzemXqwQokNCM04VLxf+5lHBNnf6iHxusDg6FOy/MNB+/UHyk1TFhCmjX0KTz8cBboYM bTutt0+KZBlXZv3OExA== 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=2026-10-01_03,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 spamscore=0 phishscore=0 bulkscore=0 adultscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610010038 Calls to idr_alloc() in __prealloc_nested() are not currently synchronized. According to the documentation [1], the caller should provide their own locking to prevent concurrent modifications to the idr to prevent bugs. Wrap the call to __prealloc_nested() in a spinlock to prevent concurrent modifications to idr. [1]: lib/idr.c Fixes: c0f00a18e2a8 ("KVM: PPC: Book3S HV Nested: Change nested guest lookup to use idr") Cc: stable@vger.kernel.org # 5.19+ Co-developed-by: Ritesh Harjani (IBM) Signed-off-by: Ritesh Harjani (IBM) Signed-off-by: Gautam Menghani --- arch/powerpc/kvm/book3s_hv_nested.c | 34 +++++++++-------------------- 1 file changed, 10 insertions(+), 24 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c index a6ff42d7666c..e893fdd24f0a 100644 --- a/arch/powerpc/kvm/book3s_hv_nested.c +++ b/arch/powerpc/kvm/book3s_hv_nested.c @@ -702,20 +702,6 @@ static struct kvm_nested_guest *__find_nested(struct kvm *kvm, int lpid) return idr_find(&kvm->arch.kvm_nested_guest_idr, lpid); } -static bool __prealloc_nested(struct kvm *kvm, int lpid) -{ - if (idr_alloc(&kvm->arch.kvm_nested_guest_idr, - NULL, lpid, lpid + 1, GFP_KERNEL) != lpid) - return false; - return true; -} - -static void __add_nested(struct kvm *kvm, int lpid, struct kvm_nested_guest *gp) -{ - if (idr_replace(&kvm->arch.kvm_nested_guest_idr, gp, lpid)) - WARN_ON(1); -} - static void __remove_nested(struct kvm *kvm, int lpid) { idr_remove(&kvm->arch.kvm_nested_guest_idr, lpid); @@ -862,21 +848,21 @@ struct kvm_nested_guest *kvmhv_get_nested(struct kvm *kvm, int l1_lpid, if (!newgp) return NULL; - if (!__prealloc_nested(kvm, l1_lpid)) { - kvmhv_release_nested(newgp); - return NULL; - } - + idr_preload(GFP_KERNEL); spin_lock(&kvm->mmu_lock); gp = __find_nested(kvm, l1_lpid); if (!gp) { - __add_nested(kvm, l1_lpid, newgp); - ++newgp->refcnt; - gp = newgp; - newgp = NULL; + if (idr_alloc(&kvm->arch.kvm_nested_guest_idr, newgp, + l1_lpid, l1_lpid + 1, GFP_NOWAIT) >= 0) { + ++newgp->refcnt; + gp = newgp; + newgp = NULL; + } } - ++gp->refcnt; + if (gp) + ++gp->refcnt; spin_unlock(&kvm->mmu_lock); + idr_preload_end(); if (newgp) kvmhv_release_nested(newgp); -- 2.52.0