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Mon, 28 Sep 2026 12:28:54 +0000 (GMT) Received: from localhost.localdomain (unknown [9.124.213.32]) by smtpav06.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 28 Sep 2026 12:28:54 +0000 (GMT) From: Amit Machhiwal To: Madhavan Srinivasan , linuxppc-dev@lists.ozlabs.org Cc: Amit Machhiwal , Nicholas Piggin , Michael Ellerman , "Christophe Leroy (CS GROUP)" , "Ritesh Harjani (IBM)" , Shrikanth Hegde , kvm-ppc@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Gautam Menghani , Harsh Prateek Bora , R Nageswara Sastry , Alexander Graf , linux-hardening@vger.kernel.org, stable@vger.kernel.org, Avi Kivity Subject: [RESEND PATCH 2/3] KVM: PPC: Book3S HV: Add preempt_disable() around virtual-mode HPTE bit-lock users Date: Mon, 28 Sep 2026 17:58:36 +0530 Message-ID: <20260928122837.8782-3-amachhiw@linux.ibm.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260928122837.8782-1-amachhiw@linux.ibm.com> References: <20260928122837.8782-1-amachhiw@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: AW1haW4tMjYwOTI4MDA0OCBTYWx0ZWRfX8orC67y5LIzZ MbkLLDkW8iKH61KD84M4h6qjsOx/DJjdHd6cqFyffYViw6+A/y1Oa3V9MTIMZtAGeNcB/CPHu1/ eJqzvflTGSL9d6b6DhZXlBMNn1UiwzE= X-Authority-Analysis: v=2.4 cv=HJ5WhYtv c=1 sm=1 tr=0 ts=6aba5d90 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=VdqzKS8jKosA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=u-HXxruZ6MoSruA0XqgA:9 X-Proofpoint-GUID: ssYpujtXTr3xZVKrx3l4RHk6LBXWie9s X-Proofpoint-ORIG-GUID: W23ZGQdjt_C1_vFOMLjSPerJtRideBdi X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwOTI4MDA0OCBTYWx0ZWRfX8vCeEXCAWkQk /CB3AUshbHRqmOKK1pv2ohPN47VtqXRpGjejRIy/nlSm2xTLaSSBLB2nYohCfjSgNIo9xuC1N8e huqQmkvEhBx4Y5EHlSiKfPnL67bZEcui77ZF4an7QRLI2O7tgQARwEufsS1RdwaALu0QsZbpKmQ 4UogiKva+Qv2JAsClFHnGAVHlT9ynl7zgmD30h5A8rcKr9w6hzoz1svaP1MKL4nA1B48cVmouDe 1PPrdKcm0X53wCpJTduLYRiZyRvyGDTXCTIXQqjRxKnv/UJmSTUTlpB13FD++LMfStcBl6RaKqy PMMm+o5ZRwY/PCsmq7I1zQXennHohdA4uunhnsx3FZ/vuh9EHx/x1+ocev9wnCezNGcHrtiqj0O 6RpzpT4jUF398dpgJcQW5gWQfM0ZVOWculo6KFZI5yFfyosXMcN08BxN+Yu4eKYp8XkBCzGDqNC ldFfnEvQImVTcJ8CIrQ== 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=2026-09-28_03,2026-09-21_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 malwarescore=0 suspectscore=0 bulkscore=0 clxscore=1015 lowpriorityscore=0 spamscore=0 impostorscore=0 phishscore=0 priorityscore=1501 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2609040000 definitions=main-2609280048 kvmppc_hv_find_lock_hpte() requires virtual-mode callers to run with preemption disabled, because it can return with HPTE_V_HVLOCK still held until the caller later unlocks the HPTE. Existing virtual-mode callers in book3s_64_mmu_hv.c already follow that rule. Two virtual-mode call paths do not: 1. kvmppc_handle_exit_hv() calls kvmppc_hpte_hv_fault() for hash-mode data-side and instruction-side faults after guest exit, with preemption already enabled. kvmppc_hpte_hv_fault() calls kvmppc_hv_find_lock_hpte() directly. 2. kvmppc_pseries_do_hcall() executes virtual-mode handlers for HPT hcalls via kvmppc_pseries_do_hpt_hcall() with preemption enabled. The handlers for H_ENTER, H_REMOVE, H_READ, H_CLEAR_MOD, H_CLEAR_REF, H_PROTECT, and H_BULK_REMOVE spin on try_lock_hpte() or lock_rmap(), and H_ENTER also reaches kvmppc_do_h_enter(), which uses arch_spin_lock() on kvm->mmu_lock. That raw lock choice is intentional because kvmppc_do_h_enter() is also used by real-mode callers, so the correct fix is to establish the proper preemption context at the virtual-mode caller boundary. If a vCPU thread is preempted while holding HPTE_V_HVLOCK, any other thread on the same CPU trying to acquire the same bit-lock can spin indefinitely. The same applies to lock_rmap() users and to the H_ENTER path while holding the raw mmu_lock. Fix this by adding preempt_disable()/preempt_enable() pairs around the two kvmppc_hpte_hv_fault() call sites in kvmppc_handle_exit_hv(), and around the kvmppc_pseries_do_hpt_hcall() invocation in kvmppc_pseries_do_hcall(). Targeting only the HPT hcall helper avoids wrapping non-HPT hcalls (such as H_RTAS, H_CONFER, H_REGISTER_VPA) that perform page faults, blocking memory allocations, or context switches. Fixes: 6165d5dd99db ("KVM: PPC: Book3S HV: add virtual mode handlers for HPT hcalls and page faults") Cc: stable@vger.kernel.org # v5.14+ Signed-off-by: Amit Machhiwal --- arch/powerpc/kvm/book3s_hv.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c index aa51968e206a..52f72f30baf0 100644 --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1212,9 +1212,11 @@ int kvmppc_pseries_do_hcall(struct kvm_vcpu *vcpu) case H_CLEAR_REF: case H_PROTECT: case H_BULK_REMOVE: + preempt_disable(); idx = srcu_read_lock(&kvm->srcu); ret = kvmppc_pseries_do_hpt_hcall(vcpu, req); srcu_read_unlock(&kvm->srcu, idx); + preempt_enable(); if (ret == H_TOO_HARD) return RESUME_HOST; break; @@ -1834,8 +1836,10 @@ static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu, else vsid = vcpu->arch.fault_gpa; + preempt_disable(); err = kvmppc_hpte_hv_fault(vcpu, vcpu->arch.fault_dar, vsid, vcpu->arch.fault_dsisr, true); + preempt_enable(); if (err == 0) { r = RESUME_GUEST; } else if (err == -1 || err == -2) { @@ -1881,8 +1885,10 @@ static int kvmppc_handle_exit_hv(struct kvm_vcpu *vcpu, else vsid = vcpu->arch.fault_gpa; + preempt_disable(); err = kvmppc_hpte_hv_fault(vcpu, vcpu->arch.fault_dar, vsid, vcpu->arch.fault_dsisr, false); + preempt_enable(); if (err == 0) { r = RESUME_GUEST; } else if (err == -1) { -- 2.54.0 (Apple Git-157)