Re: [RFC PATCH] semihosting: suspend recieving CPU when blocked (HACK, WIP)

[Paolo Bonzini]

On 17/12/19 14:42, Alex Bennée wrote:
>> Why do you need to set exception_index to something other than -1 (using
>> cpu_loop_exit_noexc for example)?
> If there is no exception to process we won't exit the main loop which we
> need to do if we want to wait until there is data to read.

Okay.

>> Using ->stop here is a bit weird, since ->stop is usually related to
>> pause_all_vcpus.
> 
> Arguably we could come up with a better API to cpu.c but this allows us
> to use cpu_resume(c->sleeping_cpu) when waking up rather than hand
> rolling our own wake-up mechanism.

But we already have the right wake-up mechanism, which is
cpu->halted/cpu_has_work.  That also makes it possible to just use
EXCP_HALTED instead of adding a new EXCP_BLOCKED.

Paolo