Re: [Qemu-devel] [PATCH, RFC] trace: implement guest tracepoint passthrough

[Blue Swirl]

On Wed, Aug 31, 2011 at 8:38 AM, Avi Kivity <address@hidden> wrote:
> On 08/26/2011 10:06 PM, Blue Swirl wrote:
>>
>> Let guests inject tracepoint data via fw_cfg device.
>>
>>
>
> At least on x86, fw_cfg is pretty slow, involving multiple exits.  IMO, for
> kvm, even one exit per tracepoint is too high.  We need to use a shared
> memory transport with a way to order guest/host events later on (by using a
> clock).

This could be an easy way, if the guest always had access to an
accurate clock, but that may not be the case.