Re: [PATCH] x86/oprof: fix !HVM && !PV32 build

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Apr 16, 2021 at 04:20:59PM +0200, Jan Beulich wrote:
> On 16.04.2021 15:41, Andrew Cooper wrote:
> > On 16/04/2021 09:16, Jan Beulich wrote:
> >> clang, at the very least, doesn't like unused inline functions, unless
> >> their definitions live in a header.
> >>
> >> Fixes: d23d792478 ("x86: avoid building COMPAT code when !HVM && !PV32")
> >> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> > 
> > I agree this will fix the build.  However, looking at the code, I'm not
> > sure the original CONFIG_COMPAT was correct.  In particular, ...
> > 
> >>
> >> --- a/xen/arch/x86/oprofile/backtrace.c
> >> +++ b/xen/arch/x86/oprofile/backtrace.c
> >> @@ -43,6 +43,7 @@ dump_hypervisor_backtrace(struct vcpu *v
> >>      return head->ebp;
> >>  }
> >>  
> >> +#ifdef CONFIG_COMPAT
> >>  static inline int is_32bit_vcpu(struct vcpu *vcpu)
> >>  {
> >>      if (is_hvm_vcpu(vcpu))
> > 
> > ... this chunk of logic demonstrates that what oprofile is doing isn't
> > related to the Xen ABI in the slightest.
> > 
> > I think OProfile is misusing the guest handle infrastructure, and
> > shouldn't be using it for this task.
> 
> I'm afraid I consider this something for another day. Both the
> original #ifdef and the one getting added here are merely
> measures to get things to build.

Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Without entering on the debate whether CONFIG_COMPAT is the correct
conditional to use it's not making the issue any worse, and it will
allow to unblock the build. We can discuss about the CONFIG_COMPAT
stuff later.

Thanks, Roger.