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=1793831900; b=E25hF+/thj9tc8ZBGkcYX9aFoFUeG+Af68M/e+Kk4N3KayTTgaA33T/WebF96OdBHrli 3fB92tim2ycrTTwCAWEAmqDVm3pOI7wx97ya27tqB65NIB56lM4kE98/rEsuQL8lzkp6w S51y5OgGRbHYkp1WZXLYocQT26KqWtvXLHZ6XS66fDnqU7rhojpGhxHfTzo3wtBRcCVdn 5ng4rctaQ46Drwpn+CL8+Z6VbQ8K46LgSoZug+pO0EyUGgpRPgr02yfaOFexQnx/zOMeW Wh8wNxjoTJZcFSsOq0IJ2pzvjdb1gp0mGFvIKYz2G/ldxJs+DnU4F4aIFN0o7ssUGig== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793831900; 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=8Hu0WhKRLNsSZqO9uiMlJFSbbpEcPjfmK+75l66UU+0=; b=bHkIvZ8J2TPd/EFR8igHY/4WiH3DZZ+2k9S2/iLkwwFDK8wo2sTXrj/FxFI1ZC4WGnAm as7ThOgB1li3QmpsfzRFp8tzjhoJuldEHj2O9Hs9AlI1IQfi0IXVAFRTRiJrN8vT2CJCT 8/2DjqQaneF1VsBf722c6Ui9krBgtOdGdYOQgrdlqAzr7c4rVPbxAPNTaZoP0MvFD9irP 5vC8JsRRCOETf96+ZldIzHVkSENLF9qKudaH/RXPqAPbiciuTMfpQoA0GxwO7Pt7raMoc eukJ4gp6F1PgAjer8fVfLZYy7BXFYWJ2w6/8bwnHg/HJrpTK1ELUUPEsY8N0pxCq/Bg== 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=nk26N7+C; 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 17E34606A85F; Wed, 4 Nov 2026 22:38:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=nk26N7+C Received: by smtp.kernel.org (Postfix) with ESMTPSA id A716F1F000C1; Wed, 4 Nov 2026 22:38:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793831899; bh=8Hu0WhKRLNsSZqO9uiMlJFSbbpEcPjfmK+75l66UU+0=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=nk26N7+CXVVNlv2pM/AspHvvMxtQUAll8ei2JyV7v/enWZ5t3lXOBliU3MCvXbHND PwD+7Mcsp7PBMAEa89HN8ETfCToTF9z9lIH0YtMia1fVFv4wzVxjNxOp7Y1cndwPLK NMMNPuBpGsdUsKFr12Sgdmm6Fpd7vfPQNDoRprEE= 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 6.18 0943/1005] KVM: PPC: Book3S HV: Add preempt_disable() around virtual-mode HPTE bit-lock users Date: Wed, 4 Nov 2026 16:11:16 -0500 Message-ID: <20261104211109.530013475@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104211043.516122098@linuxfoundation.org> References: <20261104211043.516122098@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-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 @@ -1208,9 +1208,11 @@ 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; @@ -1830,8 +1832,10 @@ 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) { @@ -1877,8 +1881,10 @@ 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) {