From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36455) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eCU9C-0006WJ-JE for qemu-devel@nongnu.org; Wed, 08 Nov 2017 12:28:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eCU98-0005Xt-9i for qemu-devel@nongnu.org; Wed, 08 Nov 2017 12:28:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41436) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eCU98-0005Xe-0F for qemu-devel@nongnu.org; Wed, 08 Nov 2017 12:28:14 -0500 Date: Wed, 8 Nov 2017 17:28:06 +0000 From: "Daniel P. Berrange" Message-ID: <20171108172806.GG12670@redhat.com> Reply-To: "Daniel P. Berrange" References: <20171030040056.11780-1-f4bug@amsat.org> <20171030082029.GY2993@localhost.localdomain> <20171108132857.GT12670@redhat.com> <1ecb6a4b-465f-0949-e039-441038f1adf8@amsat.org> <20171108165905.GN3111@localhost.localdomain> <20171108170629.GD12670@redhat.com> <20171108172547.GP3111@localhost.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20171108172547.GP3111@localhost.localdomain> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC PATCH] vl: only display available accelerators List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eduardo Habkost Cc: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Thomas Huth , Stefano Stabellini , Markus Armbruster , Peter Xu , qemu-devel@nongnu.org, "Emilio G . Cota" , Anthony Perard , Paolo Bonzini , Richard Henderson On Wed, Nov 08, 2017 at 03:25:47PM -0200, Eduardo Habkost wrote: > On Wed, Nov 08, 2017 at 05:06:29PM +0000, Daniel P. Berrange wrote: > > On Wed, Nov 08, 2017 at 02:59:05PM -0200, Eduardo Habkost wrote: > > > On Wed, Nov 08, 2017 at 01:21:33PM -0300, Philippe Mathieu-Daud=C3=A9= wrote: > > > > On 11/08/2017 10:28 AM, Daniel P. Berrange wrote: > > > > > On Mon, Oct 30, 2017 at 09:20:29AM +0100, Eduardo Habkost wrote= : > > > > >> On Mon, Oct 30, 2017 at 01:00:56AM -0300, Philippe Mathieu-Dau= d=C3=A9 wrote: > > > > >>> examples configuring with '--enable-kvm --disable-tcg' > > > > >>> > > > > >>> - before > > > > >>> > > > > >>> $ qemu-system-x86_64 -accel help > > > > >>> Possible accelerators: kvm, xen, hax, tcg > > > > >>> > > > > >>> $ qemu-system-x86_64 -accel tcg > > > > >>> qemu-system-x86_64: -machine accel=3Dtcg: No accelerator fo= und > > > > >>> > > > > >>> # qemu-system-x86_64 -accel hax > > > > >>> qemu-system-x86_64: -machine accel=3Dhax: No accelerator fo= und > > > > >>> > > > > >>> # qemu-system-x86_64 -accel xen > > > > >>> xencall: error: Could not obtain handle on privileged comma= nd interface: No such file or directory > > > > >>> xen be core: xen be core: can't open xen interface > > > > >>> can't open xen interface > > > > >>> qemu-system-x86_64: failed to initialize Xen: Operation not= permitted > > > > >>> > > > > >>> - after > > > > >>> > > > > >>> $ qemu-system-x86_64 -accel help > > > > >>> Possible accelerators: kvm > > > > >>> > > > > >>> Signed-off-by: Philippe Mathieu-Daud=C3=A9 > > > > >>> --- > > > > >>> RFC because: > > > > >>> - I don't think this is the nicest way, too much #ifdef'f= ery in main() > > > > >> > > > > >> I suggest using object_class_get_list(TYPE_ACCEL, false). > > > > >=20 > > > > > And check the result of the available() method on the returned = classes > > > > > too, to filter the results. > > > >=20 > > > > Good idea! I'll use that. > > >=20 > > > It looks like QTest is the only accelerator that implements > > > ->available(), and its return value is a build-time constant that > > > depends only on CONFIG_POSIX. > > >=20 > > > I wonder why we don't simply avoid compiling the qtest class if > > > CONFIG_POSIX is unset, making the ->available() method > > > unnecessary. > >=20 > > Yeah that does seem simpler, though I'm surprised that Xen does not > > implement the available method. Xen is an accel I'd expect to see > > compiled into an x86 build, but is only available if the host is > > actually booted under a Xen hypervisor. Likewise shouldn't kvm > > only report itself as available if the /dev/kvm actually exists. > > But maybe that's not the kind of semantics code using available() > > expects ? >=20 > Currently the only caller of ->available() calls ->init_machine() > immediately afterwards, so for the current code it doesn't matter > if the check is inside ->available() or ->init_machine(). >=20 > That said, I'm not sure we should look for /dev/kvm or check for > the Xen hypervisor when handling "-accel help". I expect help > text to tell the user what the QEMU binary supports, not what the > current host supports. Yeah, that's sensible. Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| |: https://libvirt.org -o- https://fstop138.berrange.c= om :| |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|