Re: [Qemu-devel] [PATCH 2/2] machine_parse(): list supported machine types in their registration order

[Laszlo Ersek]

On 09/22/14 14:36, Michael S. Tsirkin wrote:
> On Mon, Sep 22, 2014 at 02:29:08PM +0200, Laszlo Ersek wrote:
>> On 09/22/14 14:04, Andreas Färber wrote:
>>> Am 22.09.2014 um 13:26 schrieb Laszlo Ersek:
>>>> Based on the registration order captured in the previous patch, we
>>>> sort the ad-hoc list printed for
>>>>
>>>>   qemu-system-XXXX -M \?
>>>
>>> Agree that the order is worth sanitizing. I would however argue that
>>> registration order is not entirely stable either if you think of
>>> non-PC cases where there's dozens of source files registering one
>>> machine each. I would therefore propose alphabetical order as we do
>>> for QOM'ified CPUs.
>>
>> I did mention alphabetical order in the message of patch #1 -- in fact
>> that was what I implemented first:
>>
>>> The first idea to restore ordering is to sort the ad-hoc list in
>>> machine_parse() by "MachineClass.name". Such a name-based ordering
>>> would have to be reverse, so that more recent versioned machine types
>>> appear higher on the list than older versioned machine types (eg. with
>>> qemu-system-x86_64). However, such a reverse sort wreaks havoc between
>>> non-versioned machine types (such as those of qemu-system-aarch64).
>>
>> Simply put, it looks very ugly. Namely, if you sort it in alphabetically
>> *ascending* order, then for the x86_64 target, you get:
>>
>>> isapc                ISA-only PC
>>> none                 empty machine
>>> pc                   Standard PC (i440FX + PIIX, 1996) (alias of 
>>> pc-i440fx-2.2)
>>> pc-0.10              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.11              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.12              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.13              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.14              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.15              Standard PC (i440FX + PIIX, 1996)
>>> pc-1.0               Standard PC (i440FX + PIIX, 1996)
>>> pc-1.1               Standard PC (i440FX + PIIX, 1996)
>>> pc-1.2               Standard PC (i440FX + PIIX, 1996)
>>> pc-1.3               Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.4        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.5        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.6        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.7        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-2.0        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-2.1        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-2.2        Standard PC (i440FX + PIIX, 1996) (default)
>>> pc-q35-1.4           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-1.5           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-1.6           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-1.7           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-2.0           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-2.1           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-2.2           Standard PC (Q35 + ICH9, 2009)
>>> q35                  Standard PC (Q35 + ICH9, 2009) (alias of pc-q35-2.2)
>>
>> which is very bad / unusual. Okay, so let's sort it in alphabetically
>> descending order:
>>
>>> q35                  Standard PC (Q35 + ICH9, 2009) (alias of pc-q35-2.2)
>>> pc-q35-2.2           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-2.1           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-2.0           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-1.7           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-1.6           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-1.5           Standard PC (Q35 + ICH9, 2009)
>>> pc-q35-1.4           Standard PC (Q35 + ICH9, 2009)
>>> pc-i440fx-2.2        Standard PC (i440FX + PIIX, 1996) (default)
>>> pc-i440fx-2.1        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-2.0        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.7        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.6        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.5        Standard PC (i440FX + PIIX, 1996)
>>> pc-i440fx-1.4        Standard PC (i440FX + PIIX, 1996)
>>> pc-1.3               Standard PC (i440FX + PIIX, 1996)
>>> pc-1.2               Standard PC (i440FX + PIIX, 1996)
>>> pc-1.1               Standard PC (i440FX + PIIX, 1996)
>>> pc-1.0               Standard PC (i440FX + PIIX, 1996)
>>> pc-0.15              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.14              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.13              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.12              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.11              Standard PC (i440FX + PIIX, 1996)
>>> pc-0.10              Standard PC (i440FX + PIIX, 1996)
>>> pc                   Standard PC (i440FX + PIIX, 1996) (alias of 
>>> pc-i440fx-2.2)
>>> none                 empty machine
>>> isapc                ISA-only PC
>>
>> Okay, this is certainly bearable. However, let's see what the reverse
>> alpha sort does to aarch64:
>>
>>> z2                   Zipit Z2 (PXA27x)
>>> xilinx-zynq-a9       Xilinx Zynq Platform Baseboard for Cortex-A9
>>> virt                 ARM Virtual Machine
>>> vexpress-a9          ARM Versatile Express for Cortex-A9
>>> vexpress-a15         ARM Versatile Express for Cortex-A15
>>> versatilepb          ARM Versatile/PB (ARM926EJ-S)
>>> versatileab          ARM Versatile/AB (ARM926EJ-S)
>>> verdex               Gumstix Verdex (PXA270)
>>> tosa                 Tosa PDA (PXA255)
>>> terrier              Terrier PDA (PXA270)
>>> sx1-v1               Siemens SX1 (OMAP310) V1
>>> sx1                  Siemens SX1 (OMAP310) V2
>>> spitz                Spitz PDA (PXA270)
>>> smdkc210             Samsung SMDKC210 board (Exynos4210)
>>> realview-pbx-a9      ARM RealView Platform Baseboard Explore for Cortex-A9
>>> realview-pb-a8       ARM RealView Platform Baseboard for Cortex-A8
>>> realview-eb-mpcore   ARM RealView Emulation Baseboard (ARM11MPCore)
>>> realview-eb          ARM RealView Emulation Baseboard (ARM926EJ-S)
>>> nuri                 Samsung NURI board (Exynos4210)
>>> none                 empty machine
>>> n810                 Nokia N810 tablet aka. RX-44 (OMAP2420)
>>> n800                 Nokia N800 tablet aka. RX-34 (OMAP2420)
>>> musicpal             Marvell 88w8618 / MusicPal (ARM926EJ-S)
>>> midway               Calxeda Midway (ECX-2000)
>>> mainstone            Mainstone II (PXA27x)
>>> lm3s811evb           Stellaris LM3S811EVB
>>> lm3s6965evb          Stellaris LM3S6965EVB
>>> kzm                  ARM KZM Emulation Baseboard (ARM1136)
>>> integratorcp         ARM Integrator/CP (ARM926EJ-S)
>>> highbank             Calxeda Highbank (ECX-1000)
>>> cubieboard           cubietech cubieboard
>>> connex               Gumstix Connex (PXA255)
>>> collie               Collie PDA (SA-1110)
>>> cheetah              Palm Tungsten|E aka. Cheetah PDA (OMAP310)
>>> canon-a1100          Canon PowerShot A1100 IS
>>> borzoi               Borzoi PDA (PXA270)
>>> akita                Akita PDA (PXA270)
>>
>> Ugh? The reverse sort is painfully obvious, and the user wonders why it
>> is necessary. Why is z2 at the top, and akita at the bottom? Why is n810
>> above n800 and not below it? And so on.
>>
>> Instead, the patchset restores the behavior that had been visible before
>> commit 261747f1: programmer-controlled logical order *within* clusters,
>> and unspecified order *between* clusters.
> 
> We could add a cluster name in the API.
> Use that for sort between clusters only.
> Hmm?

That's doable if you're okay with __FILE__ as the "cluster key". Because
that way the current registration calls can go through a macro that
substitutes the "cluster key" automatically.

Otherwise, all call sites would have to be updated manually, which is
not an inviting prospect:

$ git grep -E '\<qemu_register(_pc)?_machine\>' | wc -l
115

Even if we just count the clusters, they're way too many:

$ git grep -E '\<machine_init\>' | wc -l
66

Thanks
Laszlo