On Wed, Sep 18, 2019 at 4:34 PM Alex Bennée <alex.ben...@linaro.org> wrote: > > > Dan Streetman <dan.street...@canonical.com> writes: > > > From: Dan Streetman <ddstr...@canonical.com> > > > > There is currently no default machine type for arm so one must be specified > > with --machine. This sets the 'virt' machine type as default. > > We should really have a FAQ entry for why we don't have a default for > ARM. In short unlike PC's every ARM device is different so it pays to be > precise about what you want when you invoke QEMU. Because any given > kernel/image is only likely to work on the machine it's built for.
well, that's the problem, I have no idea at all what I want; and "I" doesn't really apply completely in this situation, as the call to run qemu comes from deep inside a test suite, and can run on multiple archs, and could even be run by other people on other systems/archs. This is what I have (tentatively) come up with to handle this in the test suite: https://github.com/systemd/systemd/pull/13409/files#diff-2ea30ffea3b108e0f9c50846cfdcd4e5R197 To be fair, it's unlikely that other people would run this on an arm system, unless they were a bit more familiar with arm, and maybe would know what machine type to pick. Similarly for the testbeds that I handle for this test suite, I know that 'virt' seems to work. > > Why is virt special? It's just one of the many machines we emulate and > while it's probably the most popular these days for "something that > boots a Linux distro" why not -machine sba (when that comes)? I am certainly not the right person to pick what the default should be, but I do think there should be *some* default. If 'virt' is the most popular and/or has the widest kernel support, then it probably makes sense to make that the default. I would guess that users of qemu-system-aarch64 (or -arm) fall into 2 groups: 1. people who know about arm and know exactly what machine they want to use 2. people who don't know about arm and have no idea what machine to use group #1 of course can still pick whatever machine they want. I'm in group #2, and I suspect that like most others in the group, I did: $ qemu-system-aarch64 ... qemu-system-aarch64: No machine specified, and there is no default Use -machine help to list supported machines $ qemu-system-aarch64 -M ? ...shows long list of machines that i'm unfamiliar with... virt-2.10 QEMU 2.10 ARM Virtual Machine virt-2.11 QEMU 2.11 ARM Virtual Machine virt-2.12 QEMU 2.12 ARM Virtual Machine virt-2.6 QEMU 2.6 ARM Virtual Machine virt-2.7 QEMU 2.7 ARM Virtual Machine virt-2.8 QEMU 2.8 ARM Virtual Machine virt-2.9 QEMU 2.9 ARM Virtual Machine virt-3.0 QEMU 3.0 ARM Virtual Machine virt QEMU 3.1 ARM Virtual Machine (alias of virt-3.1) virt-3.1 QEMU 3.1 ARM Virtual Machine (aha! those "virt" machines look generic enough that they'll work...) $ qemu-system-aarch64 -M virt ... I honestly don't know if it would be better to have a FAQ on why there is no default, or just to set a default. Personally, I'd prefer just having a default. If you do decide against a default, I would suggest at least printing the url to the FAQ entry on why arm doesn't have a default, instead of just asking users to pick one out of the -M ? list. > > > > > Signed-off-by: Dan Streetman <ddstr...@canonical.com> > > --- > > hw/arm/virt.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > > index d74538b021..e9fe888ca2 100644 > > --- a/hw/arm/virt.c > > +++ b/hw/arm/virt.c > > @@ -78,6 +78,7 @@ > > mc->desc = "QEMU " # major "." # minor " ARM Virtual Machine"; \ > > if (latest) { \ > > mc->alias = "virt"; \ > > + mc->is_default = 1; \ > > } \ > > } \ > > static const TypeInfo machvirt_##major##_##minor##_info = { \ > > > -- > Alex Bennée >
