Re: [Xen-devel] [PATCH 10/10] x86/hvm: Do not enable MPX by default

[Jan Beulich <jbeulich@xxxxxxxx>]

On 26.02.2020 21:22, Andrew Cooper wrote:
> Memory Protection eXtension support has been dropped from GCC and Linux, and
> will be dropped from future Intel CPUs.
> 
> With all other default/max pieces in place, move MPX from default to max.
> This means that VMs won't be offered it by default, but can explicitly opt
> into using it via cpuid="host,mpx=1" in their vm.cfg file.
> 
> The difference as visible to the guest is:
> 
>   diff --git a/default b/mpx
>   index 0e91765d6b..c8c33cd584 100644
>   --- a/default
>   +++ b/mpx
>   @@ -13,15 +13,17 @@ Native cpuid:
>      00000004:00000004 -> 00000000:00000000:00000000:00000000
>      00000005:ffffffff -> 00000000:00000000:00000000:00000000
>      00000006:ffffffff -> 00000000:00000000:00000000:00000000
>   -  00000007:00000000 -> 00000000:009c2fbb:00000000:9c000400
>   +  00000007:00000000 -> 00000000:009c6fbb:00000000:9c000400
>      00000008:ffffffff -> 00000000:00000000:00000000:00000000
>      00000009:ffffffff -> 00000000:00000000:00000000:00000000
>      0000000a:ffffffff -> 00000000:00000000:00000000:00000000
>      0000000b:ffffffff -> 00000000:00000000:00000000:00000000
>      0000000c:ffffffff -> 00000000:00000000:00000000:00000000
>   -  0000000d:00000000 -> 00000007:00000240:00000340:00000000
>   +  0000000d:00000000 -> 0000001f:00000240:00000440:00000000
>      0000000d:00000001 -> 0000000f:00000240:00000000:00000000
>      0000000d:00000002 -> 00000100:00000240:00000000:00000000
>   +  0000000d:00000003 -> 00000040:000003c0:00000000:00000000
>   +  0000000d:00000004 -> 00000040:00000400:00000000:00000000
>      40000000:ffffffff -> 40000005:566e6558:65584d4d:4d4d566e
>      40000001:ffffffff -> 0004000e:00000000:00000000:00000000
>      40000002:ffffffff -> 00000001:40000000:00000000:00000000
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>


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