powerpc build fail

[me@tobin.cc (Tobin C. Harding)]

On Tue, Feb 21, 2017 at 09:53:01PM +1100, Tobin C. Harding wrote:
> The current (2bfe01e) torvalds git tree fails to build with the following error
> 
> arch/powerpc/kernel/time.c: In function ?running_clock?:
> arch/powerpc/kernel/time.c:712:25: error: implicit declaration of function ?cputime_to_nsecs? [-Werror=implicit-function-declaration]
>   return local_clock() - cputime_to_nsecs(kcpustat_this_cpu->cpustat[CPUTIME_STEAL]);
>                          ^
> I would like to do more than just file a bug report. Further
> investigation (cputime.h) shows that cputime_to_nsecs has a
> preprocessor guard on the config option (currently enabled)
> CONFIG_VIRT_CPU_ACCOUNTING_NATIVE. 

Mistake made, CONFIG_VIRT_CPU_ACCOUNTING_NATIVE is *not* enabled.

$ cat .config | grep CONFIG_VIRT_CPU
# CONFIG_VIRT_CPU_ACCOUNTING_NATIVE is not set
# CONFIG_VIRT_CPU_ACCOUNTING_GEN is not set

$ cat .config | grep CONFIG_PPC_PSERIES
CONFIG_PPC_PSERIES=y

> 
> CONFIG_PPC_PSERIES is also enabled.
> 
> The offending code in arch/powerpc/kernel/time.c is
> 
> #ifdef CONFIG_PPC_PSERIES
> 
> /*                                                                                    
>  * Running clock - attempts to give a view of time passing for a virtualised          
>  * kernels.                                                                           
>  * Uses the VTB register if available otherwise a next best guess.                    
>  */
> unsigned long long running_clock(void)
> {
>  	/*                                                                            
>          * Don't read the VTB as a host since KVM does not switch in host             
>          * timebase into the VTB when it takes a guest off the CPU, reading the       
>          * VTB would result in reading 'last switched out' guest VTB.                 
>          *                                                                            
>          * Host kernels are often compiled with CONFIG_PPC_PSERIES checked, it        
>          * would be unsafe to rely only on the #ifdef above.                          
>          */
> 	if (firmware_has_feature(FW_FEATURE_LPAR) &&
>             cpu_has_feature(CPU_FTR_ARCH_207S))
> 		return mulhdu(get_vtb() - boot_tb, tb_to_ns_scale) << tb_to_ns_shift;
> 
> 	/*                                                                            
>          * This is a next best approximation without a VTB.                           
>          * On a host which is running bare metal there should never be any stolen     
>          * time and on a host which doesn't do any virtualisation TB *should* equal   
>          * VTB so it makes no difference anyway.                                      
>          */
> 	return local_clock() - cputime_to_nsecs(kcpustat_this_cpu->cpustat[CPUTIME_STEAL]);
> }
> #endif
> 
> Can anyone give me a hint on this one? Where to start reading?

Removing the compile time guard allows the build to proceed, surely
this is not the correct solution though.

diff --git a/arch/powerpc/include/asm/cputime.h b/arch/powerpc/include/asm/cputime.h
index 99b5418..15482cb 100644
--- a/arch/powerpc/include/asm/cputime.h
+++ b/arch/powerpc/include/asm/cputime.h
@@ -16,7 +16,7 @@
 #ifndef __POWERPC_CPUTIME_H
 #define __POWERPC_CPUTIME_H
 
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
+
 
 #include <linux/types.h>
 #include <linux/time.h>
@@ -53,5 +53,5 @@ void arch_vtime_task_switch(struct task_struct *tsk);
 #endif
 
 #endif /* __KERNEL__ */
-#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
+
 #endif /* __POWERPC_CPUTIME_H */
diff --git a/include/linux/cputime.h b/include/linux/cputime.h
index a691dc4..f730c14 100644
--- a/include/linux/cputime.h
+++ b/include/linux/cputime.h
@@ -1,13 +1,13 @@
 #ifndef __LINUX_CPUTIME_H
 #define __LINUX_CPUTIME_H
 
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
+
 #include <asm/cputime.h>
 
 #ifndef cputime_to_nsecs
-# define cputime_to_nsecs(__ct)	\
+#define cputime_to_nsecs(__ct)	\
 	(cputime_to_usecs(__ct) * NSEC_PER_USEC)
 #endif
 
-#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
+
 #endif /* __LINUX_CPUTIME_H */

thanks,
Tobin.