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

[Blue Swirl]

On Wed, Aug 31, 2011 at 6:00 PM, Dhaval Giani <address@hidden> wrote:
> 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.

It's only available for KVM on x86, that is most certainly not enough.