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From: Peter Maydell <peter.maydell@linaro.org>
Date: Thu, 25 Jan 2018 15:10:31 +0000
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Subject: Re: [Qemu-devel] [Qemu-arm] [PATCH 0/6] arm: support -cpu max (and
 gic-version=max)
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To: Eduardo Habkost <ehabkost@redhat.com>
Cc: qemu-arm <qemu-arm@nongnu.org>, QEMU Developers <qemu-devel@nongnu.org>, "Richard W . M . Jones" <rjones@redhat.com>, "patches@linaro.org" <patches@linaro.org>

On 25 January 2018 at 14:41, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 22 January 2018 at 18:33, Eduardo Habkost <ehabkost@redhat.com> wrote:
>> About QOM type names:
>>
>> On x86, all CPU models are resolved to "<model>-<suffix>", and
>> i386 and x86_64 have different suffixes.  So the QOM type name is
>> "max-x86_64-cpu" on qemu-system-x86_64, and "max-i386-cpu" on
>> qemu-system-i386.
>
> OK. Looking at the target/arm code we do a similar suffix
> trick, but we seem to have cut-n-pasted the handling in
> aarch64_cpu_register(), so it uses the TYPE_ARM_CPU as the
> suffix, rather the TYPE_AARCH64_CPU.

...and that's not as simple a fix as I thought, because the
code in helper.c for implementing arch_query_cpu_definitions() and
arm_cpu_list() assumes it can create the QOM type name by appending
TYPE_ARM_CPU. The ARM_CPU_TYPE_NAME() macro which we use pretty
extensively also assumes the suffix is the same regardless of
what CPU type it's being applied to.

Looking at x86 it seems that TYPE_X86_CPU expands to a different
string for qemu-system-x86_64 and qemu-system-i386. I could do
that, but it seems very confusing: I would expect a QOM type
name like TYPE_FOO to always mean the same QOM type.

Given that the type names don't appear to the user, I think
we can go ahead with implementing "-cpu max" for Arm without
having to first disentangle this? "max" isn't in any worse
a position than the existing "host" and "any" types.

thanks
-- PMM