From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36251) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gA9Ru-0005d2-0K for qemu-devel@nongnu.org; Wed, 10 Oct 2018 04:02:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gA9Ri-0000Yw-Rj for qemu-devel@nongnu.org; Wed, 10 Oct 2018 04:02:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33434) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gA9Rf-0000TQ-F1 for qemu-devel@nongnu.org; Wed, 10 Oct 2018 04:02:18 -0400 References: <1538748792-19444-1-git-send-email-thuth@redhat.com> From: Thomas Huth Message-ID: Date: Wed, 10 Oct 2018 10:02:07 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable 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: Paolo Bonzini , Peter Maydell Cc: QEMU Developers On 2018-10-05 23:12, Paolo Bonzini wrote: > On 05/10/2018 16:22, Peter Maydell wrote: >> 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. >=20 > Though it probably should be extended to "whpx" and "hvf" (probably > "xen" too if !CONFIG_KVM). Sure, I was just unsure whether anybody has ever tried to compile with --disable-tcg and --disable-kvm and use one of those accelerators instead? Does it work? >>> 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). >=20 > I think it makes sense. At least RHEL has qemu-kvm but no > qemu-system-x86_64, so it has a non-upstream patch to change the > accelerator; for other distros there are two benefits: >=20 > 1) now: they could switch to a symlink Right, I think it's a good idea to avoid wrapper scripts - there is less chance to get things wrong in this case. Thomas