From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794061770; b=yaVsawPMHmwqbVoN7BJ+inKj0oN1z5bPaOTM+5MRqmiZkJfWuCRatDfgb26pqurrmt0K FvwXyurH9o7ilT+jCxPOxa5BX3pvDZ8tszp2tz65jRlBPEIFQNXm8k3vLrhKfe9f8zTk0 5DEpAskqHbPHQI3kDb8XKDS/LerGc3psfVuCqvseIlVS1ptv+3ulclFMJg982+/pXk8qd grIAlMfyZXUQXKcjX9eavNheWwsPvlujri6motvC/kAea/rDmeMiqI6VcGWVOth40EMM+ 6JOr+Ihs4yGjMSw9igceBFt27fYZuB9zI4wRlU1T9tig8BKBheqQuDNnWVZH/+cp0dw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794061770; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=3Gcm99wKy2MrLD4xYuNuxbRLTjvO4HtROfTBxuPkaYA=; b=5QvAZ1vA1ixTZTYz+tSRMsOCN78biPVVZg/068g2rPjpgQ9i3zVW4XoTv40K1P9wTjkK bOkXkqaNQ7SOhQb5YzbPW4Yp1alARYWF7md+97JlqeeDerHF+Ck/7F5yvOAtMqZhK1i9e vOyqBOtbN2D4w544h3qM8mnJpGKf52Cq2yDzBP/ssdpgbny/TenKB323DE796Qa7N6CDM Ngxb3E9JMcIkPXzNhjnT9zwHTj2H8lfoLc+6p6UB0dy0yabLfJPpAynmn130Qhd7xFPsD zkppl1hlz6f67e4k/kzmr4Vw1szvGSZuee6FsPlMig4xRYuLEYafNcyg5EE10quPx0Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=zDYSVIKF; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70005606A32D; Sat, 7 Nov 2026 14:29:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=zDYSVIKF Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2D5861F0089F; Sat, 7 Nov 2026 14:29:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1794061770; bh=3Gcm99wKy2MrLD4xYuNuxbRLTjvO4HtROfTBxuPkaYA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=zDYSVIKFDPNWLUY8ko73sElHKvf3uHv+MAajzexJ3oyJ0sFYFVcsshdA9DX+Xz5tV cJUqzog+kFyEwPPpzWe0EeN/aaxXP0sprge4Ep/NCdjTooLxp8ctig2McMTsorx4gL Tpno0aNY3dLUAWZuK5LPl+/Z19vIt8+tqaOFxQMo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Amit Machhiwal , "Ritesh Harjani (IBM)" , Madhavan Srinivasan Subject: [PATCH 6.12 0804/1536] KVM: PPC: Book3S HV: Add preempt_disable() around virtual-mode HPTE bit-lock users Date: Sat, 7 Nov 2026 08:47:00 -0500 Message-ID: <20261107135020.128063635@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261107134957.653319350@linuxfoundation.org> References: <20261107134957.653319350@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Amit Machhiwal commit abbbe5ff83e7c9ed3a4d61b73011f1df7bf87907 upstream. 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 Reviewed-by: Ritesh Harjani (IBM) Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20260928122837.8782-3-amachhiw@linux.ibm.com Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kvm/book3s_hv.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/arch/powerpc/kvm/book3s_hv.c +++ b/arch/powerpc/kvm/book3s_hv.c @@ -1192,9 +1192,11 @@ int kvmppc_pseries_do_hcall(struct kvm_v 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; @@ -1814,8 +1816,10 @@ static int kvmppc_handle_exit_hv(struct 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) { @@ -1861,8 +1865,10 @@ static int kvmppc_handle_exit_hv(struct 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) {