On Mon, Jan 13, 2020 at 07:36:41PM +0100, Manuel Bouyer wrote: > On Mon, Jan 13, 2020 at 06:33:08PM +0000, Andrew Doran wrote: > > On Mon, Jan 13, 2020 at 05:43:51PM +0100, Manuel Bouyer wrote: > > > > > On Mon, Jan 13, 2020 at 04:59:50PM +0100, Manuel Bouyer wrote: > > > > It also sets rsp and rbp. I think rbp is not set by anything else, at > > > > last > > > > in the Xen case. > > > > The different rbp value would explain why in one case we hit a KASSERT() > > > > in lwp_startup later. > > > > But I don't know what pcb_rbp contains; I couldn't find where the pcb > > > > for > > > > idlelwp is initialized. > > > > > > I tried the attached patch, which should set rsp/rbp as cpu_switchto() > > > does. It doens't cause the lwp_startup() KASSERT as calling cpu_switchto() > > > does; it also doesn't change the scheduler behavior. > > > > Wait - do you mean that everything works now? Or that everything still runs > > on CPU0? > > No, everything still runs on CPU0
Hmm, I don't understand why. I'll set up Xen and try it out. It might take me a day or two. > > The very first thing that idle_loop() does on amd64/i386 is set up the frame > > pointer - ebp/rbp. > > > > 0000000000000000 <idle_loop>: > > 0: 55 push %rbp > > 1: 48 89 e5 mov %rsp,%rbp > > 4: 41 56 push %r14 > > 6: 41 55 push %r13 > > OK, so it's OK that my patch doesn't changes anything. > And so I still don't understand the KASSERT when cpu_switchto() is called > before idle_loop(). The assertion in lwp_startup() is because I made MI changes so that prevlwp is never NULL when calling cpu_switchto(), when fixing some bugs problems MP support on !x86 and make things more correct. lwp_startup()/mi_switch() now need to unlock prevlwp after it is finished in cpu_switchto(). I never expected anybody but mi_switch() to call cpu_switchto(). Andrew