Re: [Xen-devel] [PATCH] libx86: Elide more empty CPUID leaves when serialising a policy

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.05.19 at 17:50, <andrew.cooper3@xxxxxxxxxx> wrote:
> x86_cpuid_copy_to_buffer() currently serialises the full content of the
> various subleaf unions.  While leaves 4, 0xb and 0xd don't have a concrete
> max_subleaf field, they do have well defined upper bounds.
> 
> Diffing the results of `xen-cpuid -p` shows the resutling saving:
> 
>   @@ -1,5 +1,5 @@
>    Xen reports there are maximum 114 leaves and 1 MSRs
>   -Raw policy: 93 leaves, 1 MSRs
>   +Raw policy: 38 leaves, 1 MSRs
>     CPUID:
>      leaf     subleaf  -> eax      ebx      ecx      edx
>      00000000:ffffffff -> 00000016:756e6547:6c65746e:49656e69
>   @@ -32,7 +32,7 @@ Raw policy: 93 leaves, 1 MSRs
>     MSRs:
>      index    -> value
>      000000ce -> 0000000080000000
>   -Host policy: 93 leaves, 1 MSRs
>   +Host policy: 33 leaves, 1 MSRs
>     CPUID:
>      leaf     subleaf  -> eax      ebx      ecx      edx
>      00000000:ffffffff -> 0000000d:756e6547:6c65746e:49656e69
> 
> which is mostly due to no longer writing out 64 leaves for xstate when (on
> this CoffeeLake system) 8 will do.
> 
> Extend the unit tests to cover empty and partially filled subleaf unions.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

For the lib/x86/ part
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
For the test harness part
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
No idea how else I should represent that I didn't look overly closely
at the harness additions.

Jan



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