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Date: Wed, 8 Nov 2017 14:59:05 -0200
From: Eduardo Habkost <ehabkost@redhat.com>
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References: <20171030040056.11780-1-f4bug@amsat.org>
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Subject: Re: [Qemu-devel] [RFC PATCH] vl: only display available accelerators
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To: Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= <f4bug@amsat.org>
Cc: "Daniel P. Berrange" <berrange@redhat.com>, Thomas Huth <thuth@redhat.com>, Stefano Stabellini <sstabellini@kernel.org>, Markus Armbruster <armbru@redhat.com>, Peter Xu <peterx@redhat.com>, qemu-devel@nongnu.org, "Emilio G . Cota" <cota@braap.org>, Anthony Perard <anthony.perard@citrix.com>, Paolo Bonzini <pbonzini@redhat.com>, Richard Henderson <rth@twiddle.net>

On Wed, Nov 08, 2017 at 01:21:33PM -0300, Philippe Mathieu-Daud=E9 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-Daud=E9 w=
rote:
> >>> 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 found
> >>>
> >>>   # qemu-system-x86_64 -accel hax
> >>>   qemu-system-x86_64: -machine accel=3Dhax: No accelerator found
> >>>
> >>>   # qemu-system-x86_64 -accel xen
> >>>   xencall: error: Could not obtain handle on privileged command int=
erface: 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 permi=
tted
> >>>
> >>> - after
> >>>
> >>>   $ qemu-system-x86_64 -accel help
> >>>   Possible accelerators: kvm
> >>>
> >>> Signed-off-by: Philippe Mathieu-Daud=E9 <f4bug@amsat.org>
> >>> ---
> >>> RFC because:
> >>>     - I don't think this is the nicest way, too much #ifdef'fery in=
 main()
> >>
> >> I suggest using object_class_get_list(TYPE_ACCEL, false).
> >=20
> > And check the result of the available() method on the returned classe=
s
> > too, to filter the results.
>=20
> Good idea! I'll use that.

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.

I wonder why we don't simply avoid compiling the qtest class if
CONFIG_POSIX is unset, making the ->available() method
unnecessary.

--=20
Eduardo