Re: [Qemu-ppc] [PATCH v3] spapr: add splpar hcalls H_PROD, H_CONFER

[Nicholas Piggin]

Greg Kurz's on April 17, 2019 10:01 pm:
> On Wed, 17 Apr 2019 21:20:00 +1000
> Nicholas Piggin <address@hidden> wrote:
>> [...]
>> >> @@ -1860,6 +1928,9 @@ static void hypercall_register_types(void)
>> >>      /* hcall-splpar */
>> >>      spapr_register_hypercall(H_REGISTER_VPA, h_register_vpa);
>> >>      spapr_register_hypercall(H_CEDE, h_cede);
>> >> +    spapr_register_hypercall(H_CONFER, h_confer);
>> >> +    spapr_register_hypercall(H_PROD, h_prod);
>> >> +
>> >>      spapr_register_hypercall(H_SIGNAL_SYS_RESET, h_signal_sys_reset);  
>> > 
>> > You're no longer enabling the KVM CONFER and PROD hypercalls.  Are
>> > they enabled by default, or is that an intentional change?  
>> 
> 
> AFAICT they seem to be enabled by default in HV KVM.
> 
>> Oh, it was not intentional, I must not understand how this works. Why
>> is this no longer enabling the those hcalls?
>> 
> 
> Since linux commit 699a0ea0823d ("KVM: PPC: Book3S: Controls for in-kernel 
> sPAPR hypercall handling"), in-kernel hypercalls are disabled by default
> and must be explicitely enabled by userspace. QEMU does that for some
> hypercalls already (search kvmppc_enable_set_mode_hcall() in QEMU for an
> example).

Thanks for the explanation, that's a nice feature.

> Since H_CONFER and H_PROD are listed in default_hcall_list[] in book3s_hv.c,
> no need for QEMU to enable them in KVM.

It looks like we can disable even hcalls that are in the default list
which might help with qemu H_JOIN implementation if we need to send
H_PROD to qemu to do the wake-up.

Thanks,
Nick