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

[Dhaval Giani]

On Wed, Aug 31, 2011 at 10:58 AM, Blue Swirl <address@hidden> wrote:
> 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.
>

>From what I understand, kvmclock should be good enoguh for this
purpose. That is what I am using.

Dhaval