Re: [PATCH 3/8] kvm: vmx: pass MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD down to the guest

[Paolo Bonzini]

On 10/01/2018 18:14, Jim Mattson wrote:
>>> If (a) is true, does "IBRS ALL THE TIME" usage is basically a CPU
>>> change to just create all BTB/BHB entries to be tagged with
>>> prediction-mode at creation-time and that tag to be compared to current
>>> prediction-mode when CPU attempts to use BTB/BHB?
>>
>> I hope so, and I hope said prediction mode includes PCID/VPID too.
>
> Branch prediction entries should probably be tagged with PCID, VPID,
> EP4TA, and thread ID...the same things used to tag TLB contexts.

But if so, I don't see the need for IBPB.

Paolo