RE: Qemu system mode emulation for heterogeneous SOC

[Ancuta, Cristian]

> Almost all of these are "all CPUs are identical and see basically the same 
> view of the system" setups"
On a second thought, that setup would suffice for my use case. Heterogeneous 
was just a "nice to have".

Thanks,
Cristian

-----Original Message-----
From: Peter Maydell <address@hidden> 
Sent: Wednesday, April 15, 2020 4:40 PM
To: Ancuta, Cristian <address@hidden>
Cc: address@hidden
Subject: Re: Qemu system mode emulation for heterogeneous SOC

On Wed, 15 Apr 2020 at 14:27, Ancuta, Cristian <address@hidden> wrote:
> So just to make sure I understand the MMIO stuff correctly, there's no user 
> mode support because user mode applications are talking to hardware through 
> the OS drivers and syscalls (which would run in system mode) anyway?

Correct.

> Also, is there a multi core board in the source tree that I could look at to 
> get me started ?

Lots; any board that sets its max_cpus field to something other than 1.
Almost all of these are "all CPUs are identical and see basically the same view 
of the system" setups. About the only heterogenous board I think is xlnx-zcu102 
(which has some A-class and some R-class Arm cores).

> And if there is, when emulating multiple guest cores, do they each get their 
> own threads, or are they run in a round-robin fashion on the same qemu thread?

That depends. By default, if this host-and-guest-architecture combination can 
handle it then we will create one host thread per vCPU (there's a command line 
flag to turn this off, I forget its name). Otherwise we fall back to one thread 
and round-robin.

thanks
-- PMM