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Received: from shell.armlinux.org.uk ([2001:4d48:ad52:3201:5054:ff:fe00:4ec]:38532) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1j1BsE-0007lw-Pv; Mon, 10 Feb 2020 16:25:27 +0000 Received: from linux by shell.armlinux.org.uk with local (Exim 4.92) (envelope-from ) id 1j1BsB-00081f-HJ; Mon, 10 Feb 2020 16:25:23 +0000 Date: Mon, 10 Feb 2020 16:25:23 +0000 From: Russell King - ARM Linux admin To: Marc Zyngier Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host Message-ID: <20200210162523.GF25745@shell.armlinux.org.uk> References: <20200210141324.21090-1-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200210141324.21090-1-maz@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200210_082539_995666_E20E77BB X-CRM114-Status: GOOD ( 14.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Anders Berg , Vladimir Murzin , Arnd Bergmann , kvm@vger.kernel.org, Suzuki K Poulose , Quentin Perret , Christoffer Dall , James Morse , linux-arm-kernel@lists.infradead.org, Paolo Bonzini , Will Deacon , kvmarm@lists.cs.columbia.edu, Julien Thierry Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Feb 10, 2020 at 02:13:19PM +0000, Marc Zyngier wrote: > KVM/arm was merged just over 7 years ago, and has lived a very quiet > life so far. It mostly works if you're prepared to deal with its > limitations, it has been a good prototype for the arm64 version, > but it suffers a few problems: > > - It is incomplete (no debug support, no PMU) > - It hasn't followed any of the architectural evolutions > - It has zero users (I don't count myself here) > - It is more and more getting in the way of new arm64 developments > > So here it is: unless someone screams and shows that they rely on > KVM/arm to be maintained upsteam, I'll remove 32bit host support > form the tree. One of the reasons that makes me confident nobody is > using it is that I never receive *any* bug report. Yes, it is perfect. > But if you depend on KVM/arm being available in mainline, please shout. It is only very recently that 64-bit ARM has really started to filter down to people like me, and people like me have setup systems which use 32-bit VMs under 64-bit hosts (about a year ago now.) In fact, everything that you presently see for the *.armlinux.org.uk domain now runs inside several 32-bit ARM VMs under a 64-bit ARM host. It isn't perfect; I've found issues with qemu and libvirt. One example is the rather sub-standard RTC implementation, which means if you use libvirt's managesave across a host reboot, the guests idea of time-of-day freezes while it's asleep, and resumes when the guest is reloaded - resulting in the guests time-of-day being rather wrong, sometimes to the point that NTP gives up. That becomes very painful if you use kerberos authentication, where time-of-day is important. So, just because you haven't received any bug reports doesn't mean there aren't any users; there certainly are, there are problems, but the problems are in places other than the kernel. -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up According to speedtest.net: 11.9Mbps down 500kbps up _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel