Re: [PATCH] powerpc/paravirt: Improve vcpu_is_preempted

[kernel test robot <lkp@intel.com>]

Hi Srikar,

kernel test robot noticed the following build errors:

[auto build test ERROR on tip/x86/core]
[also build test ERROR on linus/master v6.6-rc5 next-20231009]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Srikar-Dronamraju/powerpc-paravirt-Improve-vcpu_is_preempted/20231009-131957
base:   tip/x86/core
patch link:    https://lore.kernel.org/r/20231009051740.17683-1-srikar%40linux.vnet.ibm.com
patch subject: [PATCH] powerpc/paravirt: Improve vcpu_is_preempted
config: powerpc-randconfig-002-20231009 (https://download.01.org/0day-ci/archive/20231009/202310091636.lElmJkYV-lkp@intel.com/config)
compiler: powerpc-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231009/202310091636.lElmJkYV-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202310091636.lElmJkYV-lkp@intel.com/

All errors (new ones prefixed by >>):

   scripts/genksyms/parse.y: warning: 9 shift/reduce conflicts [-Wconflicts-sr]
   scripts/genksyms/parse.y: warning: 5 reduce/reduce conflicts [-Wconflicts-rr]
   scripts/genksyms/parse.y: note: rerun with option '-Wcounterexamples' to generate conflict counterexamples
   In file included from arch/powerpc/include/asm/qspinlock.h:7,
                    from arch/powerpc/include/asm/spinlock.h:7,
                    from include/linux/spinlock.h:95,
                    from include/linux/ipc.h:5,
                    from include/uapi/linux/sem.h:5,
                    from include/linux/sem.h:5,
                    from include/linux/compat.h:14,
                    from arch/powerpc/kernel/asm-offsets.c:12:
   arch/powerpc/include/asm/paravirt.h: In function 'vcpu_is_preempted':
>> arch/powerpc/include/asm/paravirt.h:130:14: error: implicit declaration of function 'lppaca_of' [-Werror=implicit-function-declaration]
     130 |         if (!lppaca_of(cpu).idle)
         |              ^~~~~~~~~
>> arch/powerpc/include/asm/paravirt.h:130:28: error: request for member 'idle' in something not a structure or union
     130 |         if (!lppaca_of(cpu).idle)
         |                            ^
   cc1: some warnings being treated as errors
   make[3]: *** [scripts/Makefile.build:116: arch/powerpc/kernel/asm-offsets.s] Error 1 shuffle=3266844477
   make[3]: Target 'prepare' not remade because of errors.
   make[2]: *** [Makefile:1287: prepare0] Error 2 shuffle=3266844477
   make[2]: Target 'prepare' not remade because of errors.
   make[1]: *** [Makefile:234: __sub-make] Error 2 shuffle=3266844477
   make[1]: Target 'prepare' not remade because of errors.
   make: *** [Makefile:234: __sub-make] Error 2 shuffle=3266844477
   make: Target 'prepare' not remade because of errors.


vim +/lppaca_of +130 arch/powerpc/include/asm/paravirt.h

   103	
   104	#define vcpu_is_preempted vcpu_is_preempted
   105	static inline bool vcpu_is_preempted(int cpu)
   106	{
   107		/*
   108		 * The dispatch/yield bit alone is an imperfect indicator of
   109		 * whether the hypervisor has dispatched @cpu to run on a physical
   110		 * processor. When it is clear, @cpu is definitely not preempted.
   111		 * But when it is set, it means only that it *might* be, subject to
   112		 * other conditions. So we check other properties of the VM and
   113		 * @cpu first, resorting to the yield count last.
   114		 */
   115	
   116		/*
   117		 * Hypervisor preemption isn't possible in dedicated processor
   118		 * mode by definition.
   119		 */
   120		if (!is_shared_processor())
   121			return false;
   122	
   123		if (!(yield_count_of(cpu) & 1))
   124			return false;
   125	
   126		/*
   127		 * If CPU has yielded but OS has not requested idle then this CPU is
   128		 * definitely preempted.
   129		 */
 > 130		if (!lppaca_of(cpu).idle)
   131			return true;
   132	

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