Re: [Qemu-devel] [PATCH] target/i386: Disable MPX support on named CPU models

[Paolo Bonzini <pbonzini@redhat.com>]

On 20/12/18 15:18, Wainer dos Santos Moschetta wrote:
> 
> On 12/20/2018 10:11 AM, Paolo Bonzini wrote:
>> MPX support is being phased out by Intel; GCC has dropped it, Linux
>> is also going to do that.  Even though KVM will have special code
>> to support MPX after the kernel proper stops enabling it in XCR0,
>> we probably also want to deprecate that in a few years.  As a start,
>> do not enable it by default for any named CPU model starting with
>> the 4.0 machine types; this include Skylake, Icelake and Cascadelake.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> ---
>>   include/hw/i386/pc.h | 29 +++++++++++++++++++++++++++++
>>   target/i386/cpu.c    | 14 +++++++-------
>>   2 files changed, 36 insertions(+), 7 deletions(-)
> 
> Side question: I didn't find on QEMU's user manual any reference to
> deprecated features for CPU models. Does that information exists
> somewhere? If not, should it be documented for the users?

It's not deprecated yet, as it won't be removed until pc-*-3.1 is
deprecated.  It may be deprecated together with pc-*-3.1, or maybe not
since TCG does implement MPX.

Paolo