On 17/10/13 12:07, Anup Patel wrote:
On Thu, Oct 17, 2013 at 2:40 PM, Peter Maydell peter.maydell@linaro.org wrote:
On 17 October 2013 09:37, Marc Zyngier marc.zyngier@arm.com wrote:
On 16/10/13 18:02, Anup Patel wrote:
The PSCI SYSTEM_OFF and SYSTEM_RESET functions are VM or Guest level functions hence cannot be emulated by the in-kernel PSCI emulation code.
Why can't we implement system-wide functionality in the kernel? I fail to see the issue here.
Because the kernel isn't emulating the whole board, and you need to power off or reset the whole board, not just the CPUs.
I'm really not keen on this approach. Having part of the PSCI implementation offloaded to userspace means we don't have a complete implementation in KVM anymore, and we end-up duplicating functionality all over the place.
Also, OFF and RESET are not PSCI specific concepts, and could be implemented in various ways. I'm more inclined to return a *standardized* exit code that the various platforms can interpret.
Maybe we should have a more generic "kernel can't handle this, toss it to userspace" API? That might also fit in with supporting guests that want to make SMC calls to an emulated monitor...
Excatly, that is what this patch does by forwarding PSCI SYSTEM_OFF and SYSTEM_RESET to user space (QEMU or KVMTOOL).
I think you missed the words standardized and generic above.
M.