Re: [PATCH v8 3/6] KVM: PPC: Book3S HV: Add support for H_RPT_INVALIDATE

[Bharata B Rao <bharata@linux.ibm.com>]

On Thu, Jul 08, 2021 at 01:58:04PM +1000, David Gibson wrote:
> On Tue, Jul 06, 2021 at 10:56:32AM +0530, Bharata B Rao wrote:
> > On Mon, Jul 05, 2021 at 02:42:33PM +1000, David Gibson wrote:
> > > On Mon, Jun 21, 2021 at 02:20:00PM +0530, Bharata B Rao wrote:
> > > > diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
> > > > index 4bc45d3ed8b0..b44f291fc909 100644
> > > > --- a/arch/powerpc/include/asm/mmu_context.h
> > > > +++ b/arch/powerpc/include/asm/mmu_context.h
> > > > @@ -124,8 +124,17 @@ static inline bool need_extra_context(struct mm_struct *mm, unsigned long ea)
> > > >  
> > > >  #if defined(CONFIG_KVM_BOOK3S_HV_POSSIBLE) && defined(CONFIG_PPC_RADIX_MMU)
> > > >  extern void radix_kvm_prefetch_workaround(struct mm_struct *mm);
> > > > +void do_h_rpt_invalidate_prt(unsigned long pid, unsigned long lpid,
> > > > +			     unsigned long type, unsigned long pg_sizes,
> > > > +			     unsigned long start, unsigned long end);
> > > >  #else
> > > >  static inline void radix_kvm_prefetch_workaround(struct mm_struct *mm) { }
> > > > +static inline void do_h_rpt_invalidate_prt(unsigned long pid,
> > > > +					   unsigned long lpid,
> > > > +					   unsigned long type,
> > > > +					   unsigned long pg_sizes,
> > > > +					   unsigned long start,
> > > > +					   unsigned long end) { }
> > > 
> > > Since the only plausible caller is in KVM HV code, why do you need the
> > > #else clause.
> > 
> > The call to the above routine is prevented for non-radix guests
> > in KVM HV code at runtime using kvm_is_radix() check and not by
> > CONFIG_PPC_RADIX_MMU. Hence the #else version would be needed.
> 
> kvm_is_radix() should evaluate to false at compile time if
> !defined(CONFIG_PPC_RADIX_MMU), in which case, no you shouldn't need
> the else version.

At least in the latest mainline, I don't see the definition of
kvm_is_radix() being conditional to CONFIG_PPC_RADIX_MMU.

Anyway this is what I see in practice if the #else version is
removed and CONFIG_PPC_RADIX_MMU is turned off:

arch/powerpc/kvm/book3s_hv.c: In function ‘kvmppc_h_rpt_invalidate’:
arch/powerpc/kvm/book3s_hv.c:983:2: error: implicit declaration of function ‘do_h_rpt_invalidate_prt’; did you mean ‘do_h_rpt_invalidate_pat’? [-Werror=implicit-function-declaration]
  983 |  do_h_rpt_invalidate_prt(id, vcpu->kvm->arch.lpid,
      |  ^~~~~~~~~~~~~~~~~~~~~~~
      |  do_h_rpt_invalidate_pat

Regards,
Bharata.