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Thu, 1 Oct 2026 10:02:29 +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 10:02:29 +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 3/3] KVM: PPC: Book3s HV: Take SRCU read lock around kvmppc_h_page_init() call Date: Thu, 1 Oct 2026 15:32:06 +0530 Message-ID: <20261001100208.1271628-4-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-Authority-Analysis: v=2.4 cv=FYWiV5+6 c=1 sm=1 tr=0 ts=6abe2fbd cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=8qrm3ZJ1U5mLyAqmLJwA:9 X-Proofpoint-Spam-Info: AW1haW4tMjYxMDAxMDAzOCBTYWx0ZWRfX5NbiIP+Uzu88 e+koKIfHsxtqtXb4BSctPqfcJMV9FktTrk2ik6fbR+wAranjKTSjFjG4kmo+6akTrziNo4+KVJr y6sI7LgTifPgPws2L1T4n80RnEofvbs= X-Proofpoint-ORIG-GUID: aOKvqtGv9dMW_m-51a8aQoqB094QNt_V X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDAxMDAzOCBTYWx0ZWRfX1D63T4Vs6CVU jd0hu29OwKIJJNjXmMz81wF0qTEyu+2NEdKlNLS4GKotwp5O5Ln3D0lOul0Paq/rwwORuP/9UNl VItvnNNiaIqOT7TJEsp5WyIIvv+rGjCoDwJuqqWWQUKIdn2Jocw5bUnnZoQMvxGwvuYLtiZECsY txyJ5SlNROG3TXR23W95pz0pVSwwgoZb8XXYOCKMEUzv0AHf2JVKRPi3ohzcgdAmUFrjWFgPdvJ 8SMH1Io0eS5skHqxzaLxGENAV3v3xiRkgmQPrwz+Q1Z5nRgoHjhQNP9Ow3uX4kfAXQME/AcVw8t oJhc2FU1hwpqj5G4FiqBzlqJ4gtKYKHnaETsGxYzslKsCA7a13BQ/dRS/GYJ6bsHvvTkxdsbB9W sqwHWuma9pYqSKAM8/59NCOvOeIZku6jMu4RFHtlSoW1lhpeTxIYDpo8ey0smRBl/HZf/+SsWFA PqG7OLjhFsZjJWV7gSw== X-Proofpoint-GUID: Mfc3wQlrzT1o662RsgRmb8ENhuArzc-h 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 adultscore=0 clxscore=1015 impostorscore=0 spamscore=0 phishscore=0 priorityscore=1501 malwarescore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2610010038 Since there is no srcu read lock around kvmppc_h_page_init(), a "suspicious rcu_dereference_check() usage" can be triggered by running host linux with CONFIG_PROVE_RCU=y and the following code in the guest: plpar_hcall_norets(H_PAGE_INIT, H_ZERO_PAGE, phys_addr, 0); ============================= WARNING: suspicious RCU usage 7.0.0-dirty #227 Not tainted ----------------------------- ./include/linux/kvm_host.h:1074 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 1 lock held by qemu-system-ppc/2093: #0: c000000354197ab0 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x10c/0xaf0 stack backtrace: CPU: 30 UID: 0 PID: 2093 Comm: qemu-system-ppc Not tainted 7.0.0-dirty #227 PREEMPT(full) Hardware name: IBM,9080-HEX POWER10 (architected) 0x800200 0xf000006 of:IBM,FW1060.60 (NH1060_158) hv:phyp pSeries Call Trace: [c00000033e1bf430] [c000000001b3dbd4] dump_stack_lvl+0xc8/0x130 (unreliable) [c00000033e1bf470] [c0000000003da964] lockdep_rcu_suspicious+0x1f4/0x290 [c00000033e1bf520] [c000000000231424] gfn_to_memslot+0x1b4/0x1c0 [c00000033e1bf560] [c00000000023637c] kvm_clear_guest+0x9c/0x110 [c00000033e1bf5c0] [c0000000002714a4] kvmppc_h_page_init+0x160/0x1a0 [c00000033e1bf610] [c00000000026c040] kvmppc_pseries_do_hcall+0x1930/0x1940 [c00000033e1bf6d0] [c00000000026fb18] kvmppc_vcpu_run_hv+0x268/0x800 [c00000033e1bf7a0] [c000000000246b30] kvmppc_vcpu_run+0x30/0x50 [c00000033e1bf7c0] [c000000000241ed4] kvm_arch_vcpu_ioctl_run+0x364/0x530 [c00000033e1bf860] [c00000000022b870] kvm_vcpu_ioctl+0x1b0/0xaf0 [c00000033e1bfa50] [c0000000009b4514] sys_ioctl+0x144/0x190 [c00000033e1bfab0] [c000000000034330] system_call_exception+0x170/0x370 [c00000033e1bfe50] [c00000000000d05c] system_call_vectored_common+0x15c/0x2ec Fix this by taking a srcu read lock around kvmppc_h_page_init(). Fixes: 2d34d1c3bbfd ("KVM: PPC: Book3S HV: Implement virtual mode H_PAGE_INIT handler") Cc: stable@vger.kernel.org # 5.2+ Signed-off-by: Gautam Menghani --- arch/powerpc/kvm/book3s_hv.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index dbac3573b2c8..8678a93bac51 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1386,9 +1386,11 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) ret = kvmhv_copy_tofrom_guest_nested(vcpu); break; case H_PAGE_INIT: + kvm_vcpu_srcu_read_lock(vcpu); ret = kvmppc_h_page_init(vcpu, kvmppc_get_gpr(vcpu, 4), kvmppc_get_gpr(vcpu, 5), kvmppc_get_gpr(vcpu, 6)); + kvm_vcpu_srcu_read_unlock(vcpu); break; case H_SVM_PAGE_IN: ret = H_UNSUPPORTED; -- 2.52.0