Re: [Qemu-devel] [PATCH 3/3] target-i386: replace cpuid_*features fields with a feature word array

["Andreas Färber" <afaerber@suse.de>]

Am 12.12.2012 23:22, schrieb Eduardo Habkost:
> This replaces the feature-bit fields on both X86CPU and x86_def_t
> structs with an array.
> 
> With this, we will be able to simplify code that simply does the same
> operation on all feature words (e.g. kvm_check_features_against_host(),
> filter_features_for_kvm(), add_flagname_to_bitmaps(), and CPU
> feature-bit property lookup/registration).
> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> This patch was created solely using a sed script and no manual changes,
> to try to avoid mistakes while converting the code, and make it easier
> to rebase if necessary. The sed script can be seen at:
>   https://gist.github.com/4271991
> ---
>  hw/kvm/clock.c            |   2 +-
>  linux-user/elfload.c      |   2 +-
>  linux-user/main.c         |   4 +-
>  target-i386/cpu.c         | 578 +++++++++++++++++++++++-----------------------
>  target-i386/cpu.h         |  30 +--
>  target-i386/helper.c      |   4 +-
>  target-i386/kvm.c         |   5 +-
>  target-i386/misc_helper.c |  14 +-
>  target-i386/translate.c   |  10 +-
>  9 files changed, 331 insertions(+), 318 deletions(-)

I wonder, if we're touching all these lines anyway, can't we place the
new feature array directly into X86CPU? As far as I see the features are
never changed at runtime, so the only reason to have them in the
instance is the command-line-supplied overrides.

The clock code using first_cpu looks solvable; what about CR4 and MSR
helpers, how performance-sensitive are they? (if they're not yet using
X86CPU for something else)

With the proposed variable change env -> cpu it would not be fully
sed'able, but as a maintainer I need to review the whole patch anyway.

Either way since this change affects not just the core CPU that I have
started to maintain I feel I should give other target-i386 stakeholders
(Blue, Aurélien, malc, ...) sufficient time to object, so not before
Christmas realistically.

Regards,
Andreas

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