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Date: Fri, 27 Jul 2012 15:00:00 +0100
Message-ID: <CAFEAcA-PSQ+oVf786yycHq_8W6cuN4QPLLb_fGtriykFPGz0Rg@mail.gmail.com>
From: Peter Maydell <peter.maydell@linaro.org>
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Subject: Re: [Qemu-devel] [PATCH 5/7] qapi: add query-cpudefs command
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: libvir-list@redhat.com, Markus Armbruster <armbru@redhat.com>, Alexander Graf <agraf@suse.de>, qemu-devel@nongnu.org, Eric Blake <eblake@redhat.com>

On 27 July 2012 14:37, Anthony Liguori <aliguori@us.ibm.com> wrote:
> This command attempts to map to the behavior of -cpu ?.  Unfortunately, the
> output of this command differs wildly across targets.

I've never really understood why so much of the cpu selection
logic is deferred to target-*...

> To accomodate this, we use a weak symbol to implement a default version of the
> command that fails with a QERR_NOT_SUPPORTED error code.  Targets can then
> override and implement this command if it makes sense for them.

This is a bit of a weak reason (boom boom!) for requiring a platform
specific thing like weak symbols, though, and it's not how we handle
similar existing cases (eg see the configure/makefile logic for
memory_mapping.c vs memory_mapping-stub.c).

If having separate configure/make stuff for each of these things
sounds a bit heavyweight, we could just have a target-stubs.c which
#includes cpu.h and has a lot of
#ifndef TARGET_QUERY_CPUDEFS
[stub version]
#endif
#ifndef TARGET_GET_MEMORY_MAPPING
[stub version]
#endif

etc.

-- PMM