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

[Greg Kurz]

On Wed, 17 Apr 2019 22:47:34 +1000
David Gibson <address@hidden> wrote:

> 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.
> 

Neither do the two previous versions of this patch actually, hence
my questioning... No big deal :)

pgpxQiM1gATLU.pgp
Description: OpenPGP digital signature