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Mon, 12 Oct 2026 08:29:49 +0000 (GMT) Received: from li-fbf77acc-29ba-11b2-a85c-e8e934f50a46.ibmuc.com (unknown [9.39.28.91]) by smtpav02.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 12 Oct 2026 08:29:49 +0000 (GMT) From: Gautam Menghani To: maddy@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au, chleroy@kernel.org, sshegde@linux.ibm.com, amachhiw@linux.ibm.com Cc: linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH v3 4/4] KVM: PPC: Book3S HV: Take SRCU read lock around kvmppc_h_page_init() call Date: Mon, 12 Oct 2026 13:59:20 +0530 Message-ID: <20261012082922.218799-5-gautam@linux.ibm.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261012082922.218799-1-gautam@linux.ibm.com> References: <20261012082922.218799-1-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-Spam-Info: AW1haW4tMjYxMDEyMDAzMiBTYWx0ZWRfX5gxxItVbleqO lZCmtHY0463SDQ3qVxV6aldl5Sdirs6sxY/3OJRIwU2behwNKE09fxBE6m7YGNkiM7mQf7Isa1U dp7ROAgczzQbnbRZmOa4ns3J/kz4kWg= X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMDEyMDAzMiBTYWx0ZWRfX9se1/7+FhEJU VLCP/DTYc9d0Bl55w46DGC+2pXcL4ms0ZgKvPqqCDA210KYs3o5fEOPB8AtFNI10djaJLMxGvp9 uClba3y0KMufTeDOXFLip0ICRwJ9RdyQwM7Og0TdAf/eagJjV7bE5ZoDV1ezwcN4eDwMTMymP7w GYg9aQ7cq0fiXJaQBL/p4wMtcWvgO/F7uyDBLUDJneXLgos5YVn3gjPkPHcdI3n6AfACgwHo8Hy ndnY60JdFiAJZ9rW7z2n+vFFCPDjbRL62m00NiSZN0LW8W49jtVl14Ijh1sDURVYLFgR8cuDMRX pyTMmZ8sPsiafkuGS0cjOVVZOanQBK0AZyjWkWgSltZSOwmRskyAqjeI9gtSrSUded5pIyh052v rT85B1E336O6W3/VHM98JSxltbx3AnfdGbQBrxMR+6ZuY51i0EmHvH5Fc+B7FauB/6L45ViSQt5 +AuJ1RqEGKQjnf9vQkA== X-Authority-Analysis: v=2.4 cv=E6pYNqdl c=1 sm=1 tr=0 ts=6acc9a85 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=660iZSQnnn4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=RzCfie-kr_QcCd8fBx8p:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=8qrm3ZJ1U5mLyAqmLJwA:9 X-Proofpoint-ORIG-GUID: WmVtHqfYA1TyRnHbNzvvQkL8uj0Kqbwf X-Proofpoint-GUID: 0dYAFVYwNcwxV_QQkMSbWHgSaFWr0xmE 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=2026-10-12_02,2026-10-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 phishscore=0 clxscore=1015 bulkscore=0 priorityscore=1501 spamscore=0 adultscore=0 suspectscore=0 malwarescore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2610080000 definitions=main-2610120032 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 --- v3: 1. Use srcu_read_{lock/unlock} instead of the vcpu_srcu* variants (Ritesh) v2: None 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 de05d721edc4..3ed033d4f80f 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: + idx = srcu_read_lock(&kvm->srcu); ret = kvmppc_h_page_init(vcpu, kvmppc_get_gpr(vcpu, 4), kvmppc_get_gpr(vcpu, 5), kvmppc_get_gpr(vcpu, 6)); + srcu_read_unlock(&kvm->srcu, idx); break; case H_SVM_PAGE_IN: ret = H_UNSUPPORTED; -- 2.54.0