On 05/05/2018 19:22, Nadav Amit wrote:
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.
Hmm, I suppose we need to disable -fno-tracer globally... Has this changed in recent versions of GCC?
Paolo