From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52846) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g9rz9-0005Pr-BG for qemu-devel@nongnu.org; Tue, 09 Oct 2018 09:23:40 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g9rz8-0001fR-5T for qemu-devel@nongnu.org; Tue, 09 Oct 2018 09:23:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:43670) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1g9rz7-0001cq-Pb for qemu-devel@nongnu.org; Tue, 09 Oct 2018 09:23:38 -0400 References: <1538748792-19444-1-git-send-email-thuth@redhat.com> <875zybzdzm.fsf@dusky.pond.sub.org> <87zhvntg6k.fsf@dusky.pond.sub.org> From: Thomas Huth Message-ID: Date: Tue, 9 Oct 2018 15:23:32 +0200 MIME-Version: 1.0 In-Reply-To: <87zhvntg6k.fsf@dusky.pond.sub.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] accel: Improve selection of the default accelerator List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster , Peter Maydell Cc: Paolo Bonzini , QEMU Developers On 2018-10-09 15:14, Markus Armbruster wrote: > Markus Armbruster writes: > >> Peter Maydell writes: >> >>> On 5 October 2018 at 15:13, Thomas Huth wrote: >>>> When compiling with "--disable-tcg", we currently still use "tcg" >>>> as default accelerator. "kvm" should be used in this case instead. >>> >>> This part is non-controversial and makes good sense. >> >> Agreed. >> >>>> Also, some downstream distros provide QEMU binaries which have "kvm" >>>> in their names (e.g. "qemu-kvm" on RHEL or "kvm" on Ubuntu) that use >>>> KVM by default - and some users might want to do something similar >>>> with upstream binaries, too. Accomodate them by using "kvm:tcg" as >>>> default when we detect such a binary name. >>> >>> This part is much riskier and less clearly a good plan -- >>> do we really want our behaviour to vary based on the name >>> of the executable? Distros who want that sort of qemu-kvm >>> wrapper generally are providing it already (the Ubuntu one >>> is a 2-line shell script). >> >> I hate it when argv[0] affects behavior[*]. I hate shell wrappers less. >> >> If a system provides just one qemu executable, and its default >> accelerator should be something other than tcg:kvm, then there's a use > > Correction: "other than tcg". See configure_accelerator(). > > Remind me, why is "tcg" a good default? "It's been always like this and we're keen on backward compatibility" ? Thomas