Re: [Qemu-devel] [qom-cpu PATCH 7/7] target-i386: Replace cpuid_*features fields with a feature word array

[Igor Mammedov]

On Mon, 15 Apr 2013 16:25:40 -0300
Eduardo Habkost <address@hidden> wrote:

> 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(), CPU feature-bit
> property lookup/registration, and the proposed "feature-words" property)
> 

table of mapping *features to feature-words would nice here for review at
least.

The rest below could go to ---/nNotes: section

> This should also help avoid bugs like the ones introduced when we added
> cpuid_7_0_ebx_features. Today, adding a new feature word to the code
> requires chaning 5 or 6 different places in the code, and it's very easy
> to miss a problem when we forget to update one of those parts. See, for
> example:
> 
>  * The bug solved by commit ffa8c11f0bbf47e1b7a3a62f97bc1da591c6734a;
>    (CPUID 7 leaf was not being filtered based on host capabilities)
>  * The bug solved by commit 07ca59450c9a0c5df65665ce46aa8487af59a1dd
>    (check/enforce flags were not checking all feature flags)
> 
> Signed-off-by: Eduardo Habkost <address@hidden>