From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35801) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eCU6x-0005DS-Nw for qemu-devel@nongnu.org; Wed, 08 Nov 2017 12:26:05 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eCU6u-0004oM-G2 for qemu-devel@nongnu.org; Wed, 08 Nov 2017 12:25:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52192) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eCU6u-0004nZ-6V for qemu-devel@nongnu.org; Wed, 08 Nov 2017 12:25:56 -0500 Date: Wed, 8 Nov 2017 15:25:47 -0200 From: Eduardo Habkost Message-ID: <20171108172547.GP3111@localhost.localdomain> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20171108170629.GD12670@redhat.com> 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: "Daniel P. Berrange" Cc: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , 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 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=E9 wr= ote: > > > 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-Daud=E9= 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 foun= d > > > >>> > > > >>> # qemu-system-x86_64 -accel hax > > > >>> qemu-system-x86_64: -machine accel=3Dhax: No accelerator foun= d > > > >>> > > > >>> # qemu-system-x86_64 -accel xen > > > >>> xencall: error: Could not obtain handle on privileged command= 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 p= ermitted > > > >>> > > > >>> - after > > > >>> > > > >>> $ qemu-system-x86_64 -accel help > > > >>> Possible accelerators: kvm > > > >>> > > > >>> Signed-off-by: Philippe Mathieu-Daud=E9 > > > >>> --- > > > >>> RFC because: > > > >>> - I don't think this is the nicest way, too much #ifdef'fer= y in main() > > > >> > > > >> I suggest using object_class_get_list(TYPE_ACCEL, false). > > > >=20 > > > > And check the result of the available() method on the returned cl= asses > > > > 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 ? 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(). 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. --=20 Eduardo