On Fri, 4 Mar 2016 11:19:33 +0000 Stefan Hajnoczi <stefa...@gmail.com> wrote:
> > 2. Build a trace-cmd-server > > > > Which does the following: > > > > 1. Receive trace-cmd record commands from a guest, > > to be performed in the host > > Sometimes the opposite is desirable: the host controls tracing inside > the guest. Any thoughts on this use case? My idea for a trace-cmd server, is to have a --client operation, for running on the guest. trace-cmd server --client <connection> The connection will be some socket, either network or something directly attached to the host. Then on the host, we can have trace-cmd server --connect <guest> Where the server will create a connection to the guest. And then, you could run on the host: trace-cmd record <host-events> --connect <guest> <guest-events> And this will start recording host events, and then connect to the local server that connects to the guest(s) and that will start tracing on the guest as well. Then events on the guest will be passed to the host server. Something like this is my idea. We can work out the details on the best way to get things working. We may be able to eliminate the host server middle man. But I envision that we need a trace-cmd server running on the guest to start off the commands. The problem I have with the guest server, and something that we may be able to fix later on, but should always keep it in the back of our minds, is the security issue. For this to work, the guest server needs to run as root. It will have an open socket (network or to host), that will enable tracing on the guest. There needs to be some sort of verification on that connection to prevent anyone from connecting to it. In the protocol for the connection between guest and host, I'll currently add a "security" feature, that will allow the guest to tell whomever is connecting to it, what type of security feature it wants. For now it will be TRACE_CMD_NO_SECURITY. But that will have to change in the future. -- Steve > > > 2. Read the TSC offset for vCPUs being traced > > > > 3. Read the CPU frequency for --ts2secs > > > > 4. Receive the guest.dat from the guest and store it together > > with the host's > > > > I'd suggest the default communication between guest and > > host be via networking. Then we add vsock support when it's > > available.
