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

[David Gibson]

On Wed, Apr 17, 2019 at 02:01:29PM +0200, Greg Kurz wrote:
> 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).
> 
> 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.

Ah, ok.  Oops, that means the guest environment has been visibly
different for KVM and TCG all this time, which isn't great.

> Not sure about David's "no longer" wording though.


"no longer" meaning the previous patch version had some
kvmppc_enable_hcall(), but this version doesn't.

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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