On 1 September 2014 10:20, Christoffer Dall [off-list ref] wrote:

On Fri, Aug 29, 2014 at 06:39:09PM +0100, Peter Maydell wrote:

quoted

Talking with Ard I realised that there's actually a hole in the
specification of this new ABI. Did we intend these shutdown
and reset exits to be:
 (1) requests from the guest for the shutdown/reset to be
   scheduled in the near future (and we'll continue to execute
   the guest until the shutdown actually happens)
 (2) requests for shutdown/reset right now, with no further
   guest instructions to be executed

?

As currently implemented in QEMU we get behaviour (1),
but I think the kernel PSCI implementation assumes
behaviour (2). Who's right?

For the arm/arm64 use of this API (currently the only one?) the host
would not break or anything like that if you keep executing the VM, but
the guest will expect that no other instructions are executed after this
call.

Well, if we do that then between QEMU and KVM we've
violated the PSCI ABI we're supposed to provide, so somebody
is wrong :-)

I guess that since the kernel already implements "assume
userspace won't resume the guest vcpu" the path of least
resistance is to make userspace follow that.

What does kvmtool do here (if it implements PSCI shutdown
and reset at all)?

thanks
-- PMM