Re: [patch v2 3/8] KVM: x86: add Intel processor trace virtualization mode

[Paolo Bonzini]

On 30/10/2017 23:05, Luwei Kang wrote:
> +	if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_PT_USE_GPA) ||
> +		!(_vmexit_control & VM_EXIT_CLEAR_IA32_RTIT_CTL) ||
> +		!(_vmentry_control & VM_ENTRY_LOAD_IA32_RTIT_CTL)) {
> +		_cpu_based_2nd_exec_control &= ~SECONDARY_EXEC_PT_USE_GPA;

Also, you are not checking anywhere if the SUPPRESS_PIP controls are
available.  This is probably the best place.

> +		_vmexit_control &= ~VM_EXIT_CLEAR_IA32_RTIT_CTL;
> +		_vmentry_control &= ~VM_ENTRY_LOAD_IA32_RTIT_CTL;

These two are not needed; disabling SECONDARY_EXEC_PT_USE_GPA is enough.
The tracing mode will revert to PT_SYSTEM, which does not use the
load/clear RTIT_CTL controls.

Paolo

> +	}
> +