Re: [PATCH v7 09/13] KVM: x86: Implement Intel Processor Trace context switch

[Paolo Bonzini]

On 04/05/2018 12:29, Alexander Shishkin wrote:
> On Thu, May 03, 2018 at 08:08:39PM +0800, Luwei Kang wrote:
>> +static void pt_guest_enter(struct vcpu_vmx *vmx)
>> +{
>> +	if (pt_mode == PT_MODE_HOST || pt_mode == PT_MODE_HOST_GUEST)
>> +		rdmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
>> +
>> +	if (pt_mode == PT_MODE_HOST_GUEST &&
>> +		vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) {
>> +		wrmsrl(MSR_IA32_RTIT_CTL, 0);
>> +		pt_save_msr(&vmx->pt_desc.host, vmx->pt_desc.range_cnt);
>> +		pt_load_msr(&vmx->pt_desc.guest, vmx->pt_desc.range_cnt);
>> +	}
>> +}
>> +
>> +static void pt_guest_exit(struct vcpu_vmx *vmx)
>> +{
>> +	if (pt_mode == PT_MODE_HOST_GUEST &&
>> +		vmx->pt_desc.guest.ctl & RTIT_CTL_TRACEEN) {
>> +		pt_save_msr(&vmx->pt_desc.guest, vmx->pt_desc.range_cnt);
>> +		pt_load_msr(&vmx->pt_desc.host, vmx->pt_desc.range_cnt);
>> +	}
>> +
>> +	if (pt_mode == PT_MODE_HOST || pt_mode == PT_MODE_HOST_GUEST)
>> +		wrmsrl(MSR_IA32_RTIT_CTL, vmx->pt_desc.host.ctl);
>> +}
> 
> This means that a host PT event won't get the guest traces and won't get
> any notification as to what'd happened or why. At the minimum we need to
> send a PARTIAL AUX record at the pt_guest_enter(), when we turn the host
> tracing off.

How do you do that? :)

Paolo