From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Fedin Subject: RE: [RFC] Handling CP15 timer without in-kernel irqchip Date: Fri, 02 Oct 2015 13:18:55 +0300 Message-ID: <00cc01d0fcfb$bf8994c0$3e9cbe40$@samsung.com> References: <00a001d0fce3$f76e2170$e64a6450$@samsung.com> <560E4EC4.5050101@redhat.com> <560E56DC.6020406@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 1610A41289 for ; Fri, 2 Oct 2015 06:17:19 -0400 (EDT) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tBBCidW1DSTI for ; Fri, 2 Oct 2015 06:17:17 -0400 (EDT) Received: from mailout1.w1.samsung.com (mailout1.w1.samsung.com [210.118.77.11]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 452BE4126B for ; Fri, 2 Oct 2015 06:17:16 -0400 (EDT) Received: from eucpsbgm2.samsung.com (unknown [203.254.199.245]) by mailout1.w1.samsung.com (Oracle Communications Messaging Server 7.0.5.31.0 64bit (built May 5 2014)) with ESMTP id <0NVL00CBY8NL8HA0@mailout1.w1.samsung.com> for kvmarm@lists.cs.columbia.edu; Fri, 02 Oct 2015 11:18:57 +0100 (BST) In-reply-to: <560E56DC.6020406@redhat.com> Content-language: ru List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: 'Paolo Bonzini' , 'Peter Maydell' Cc: 'Marc Zyngier' , kvmarm@lists.cs.columbia.edu, 'kvm-devel' List-Id: kvmarm@lists.cs.columbia.edu Hello! > How do boards other than 'virt' work when emulated without KVM? Under "emulated without KVM" we normally suppose full software emulation (known in qemu as TCG). In this case CPU code is interpreted, and KVM is not used at all. Some boards (like vexpress) have own platform-specific timer, so they can work under KVM without CP15 timer. In order to make it working one should either disable CP15 timer in guest .config or remove the node from device tree. CP15 timer never worked in this configuration (KVM without irqchip). > It must be possible to emulate the physical timer in QEMU. Of course it is, and with TCG it works. But we currently cannot use it with KVM because KVM assumes that it emulates all CP15 (or system) registers by itself, and never hands any of them outside. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia