Messages in this thread | | | Subject | Re: [PATCH] compiler-gcc: disable -ftracer for __noclone functions | From | Nadav Amit <> | Date | Sat, 5 May 2018 10:22:10 -0700 |
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Paolo Bonzini <pbonzini@redhat.com> wrote:
> -ftracer can duplicate asm blocks causing compilation to fail in > noclone functions. For example, KVM declares a global variable > in an asm like > > asm("2: ... \n > .pushsection data \n > .global vmx_return \n > vmx_return: .long 2b"); > > and -ftracer causes a double declaration. > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Michal Marek <mmarek@suse.cz> > Cc: stable@vger.kernel.org > Cc: kvm@vger.kernel.org > Reported-by: Linda Walsh <lkml@tlinx.org> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > include/linux/compiler-gcc.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h > index 22ab246feed3..eeae401a2412 100644 > --- a/include/linux/compiler-gcc.h > +++ b/include/linux/compiler-gcc.h > @@ -199,7 +199,7 @@ > #define unreachable() __builtin_unreachable() > > /* Mark a function definition as prohibited from being cloned. */ > -#define __noclone __attribute__((__noclone__)) > +#define __noclone __attribute__((__noclone__, __optimize__("no-tracer")))
[ Bringing the thread back from the dead for context ]
Setting different optimization attributes to certain functions apparently prevents gcc from inlining functions with different “optimizations”. This results in poor compilation - most notably of vmx_vcpu_run() - and causes short functions such as to_vmx() not to be inlined.
Regards, Nadav
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