From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53414) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fBlU1-0008ST-GB for qemu-devel@nongnu.org; Thu, 26 Apr 2018 14:19:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fBlTx-0005BS-V3 for qemu-devel@nongnu.org; Thu, 26 Apr 2018 14:19:05 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:46276 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fBlTx-0005Af-Qf for qemu-devel@nongnu.org; Thu, 26 Apr 2018 14:19:01 -0400 References: <20180425153343.24023-1-alex.bennee@linaro.org> <87604ekl0c.fsf@linaro.org> From: Thomas Huth Message-ID: <2f69532c-8651-ef67-0910-1fad91808608@redhat.com> Date: Thu, 26 Apr 2018 20:18:52 +0200 MIME-Version: 1.0 In-Reply-To: <87604ekl0c.fsf@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC PATCH] hw/core: expand description of null-machine List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?UTF-8?Q?Alex_Benn=c3=a9e?= Cc: Marcel Apfelbaum , peter.maydell@linaro.org, qemu-devel@nongnu.org, Eduardo Habkost On 26.04.2018 18:09, Alex Benn=C3=A9e wrote: >=20 > Thomas Huth writes: >=20 >> On 25.04.2018 17:33, Alex Benn=C3=A9e wrote: >>> People following old instructions for QEMU get the message "No machin= e >>> specified, and there is no default" and run -machine help to pick a >>> new machine. Lay people might consider the null-machine to be such a >>> basic starting point but they won't get far. This leads to confusion, >>> see https://bugs.launchpad.net/qemu/+bug/1766896 as an example. >>> >>> I'm open to better words - I figured "THIS PROBABLY ISN'T WHAT YOU >>> WANT" seemed less helpful though. >>> >>> Signed-off-by: Alex Benn=C3=A9e >>> --- >>> hw/core/null-machine.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/hw/core/null-machine.c b/hw/core/null-machine.c >>> index cde4d3eb57..72f0815045 100644 >>> --- a/hw/core/null-machine.c >>> +++ b/hw/core/null-machine.c >>> @@ -50,7 +50,7 @@ static void machine_none_init(MachineState *mch) >>> >>> static void machine_none_machine_init(MachineClass *mc) >>> { >>> - mc->desc =3D "empty machine"; >>> + mc->desc =3D "empty machine (for probing/QMP)"; >> >> Actually, with certain CPUs, you can really use the "none" machine as = a >> pure instruction set testing system. For example, on m68k, there used = to >> be an explicit "dummy" machine for this job, and we removed it in favo= ur >> of the "none" machine: >> >> https://git.qemu.org/?p=3Dqemu.git;a=3Dcommitdiff;h=3D22f2dbe7eaf3e12e= 38c9c210 >=20 > Ahh OK. Do you know what other CPUs can be used in this way? I think it should be possible with at least all the boards that have a "sim" machine, e.g. xtensa, mips, moxie and openrisc. >> So I'd rather not add such wording. We should rather fix those segfaul= ts >> instead (QEMU should never segfault - in case a device can not be used >> with the "none" machine, there rather should be an error message inste= ad). >=20 > Hmm the ARM world is complicated by peripherals that are on-chip but no= t > part of the "CPU". I wonder if this is a edge case for our modelling? > Should for example -cpu cortex-m3 imply additional peripherals and how > do we handle that in the -m none case? I don't think it makes sense to instantiate e.g. an interrupt controller with the "none" machine automatically ... so the raw cortex-m3 core should either be usable without that, too, or there just should be an error message instead of a crash when the additional hardware is not available - since it's not that urgent that the raw cortex-m3 core is usable with the none machine, is it? Thomas