Hi Michael, Thank you for the patch! Yet something to improve: [auto build test ERROR on arm64/for-next/core] [also build test ERROR on tip/timers/core efi/next linus/master v5.11 next-20210218] [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] url: https://github.com/0day-ci/linux/commits/Michael-Kelley/Enable-Linux-gues... base: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core config: arm64-randconfig-r012-20210218 (attached as .config) compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project c9439ca36342fb6013187d0a69aef92736951476) reproduce (this is a W=1 build): wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross chmod +x ~/bin/make.cross # install arm64 cross compiling tool for clang build # apt-get install binutils-aarch64-linux-gnu # https://github.com/0day-ci/linux/commit/660cf2b87076569fd159d012c005e1719... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Michael-Kelley/Enable-Linux-guests-on-Hyper-V-on-ARM64/20210219-072336 git checkout 660cf2b87076569fd159d012c005e171994ea34d # save the attached .config to linux build tree COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=arm64 If you fix the issue, kindly add following tag as appropriate Reported-by: kernel test robot <lkp(a)intel.com&gt; All errors (new ones prefixed by >>): In file included from arch/arm64/kernel/setup.c:52: In file included from arch/arm64/include/asm/mshyperv.h:71: HVMSG_NONE) != old_msg_type) ^ hv_signal_eom(); ^ 2 errors generated. vim +/HVMSG_NONE +71 include/asm-generic/mshyperv.h 765e33f5211ab6 Michael Kelley 2019-05-30 55 765e33f5211ab6 Michael Kelley 2019-05-30 56 765e33f5211ab6 Michael Kelley 2019-05-30 57 /* Free the message slot and signal end-of-message if required */ 765e33f5211ab6 Michael Kelley 2019-05-30 58 static inline void vmbus_signal_eom(struct hv_message *msg, u32 old_msg_type) 765e33f5211ab6 Michael Kelley 2019-05-30 59 { 765e33f5211ab6 Michael Kelley 2019-05-30 60 /* 765e33f5211ab6 Michael Kelley 2019-05-30 61 * On crash we're reading some other CPU's message page and we need 765e33f5211ab6 Michael Kelley 2019-05-30 62 * to be careful: this other CPU may already had cleared the header 765e33f5211ab6 Michael Kelley 2019-05-30 63 * and the host may already had delivered some other message there. 765e33f5211ab6 Michael Kelley 2019-05-30 64 * In case we blindly write msg->header.message_type we're going 765e33f5211ab6 Michael Kelley 2019-05-30 65 * to lose it. We can still lose a message of the same type but 765e33f5211ab6 Michael Kelley 2019-05-30 66 * we count on the fact that there can only be one 765e33f5211ab6 Michael Kelley 2019-05-30 67 * CHANNELMSG_UNLOAD_RESPONSE and we don't care about other messages 765e33f5211ab6 Michael Kelley 2019-05-30 68 * on crash. 765e33f5211ab6 Michael Kelley 2019-05-30 69 */ 765e33f5211ab6 Michael Kelley 2019-05-30 70 if (cmpxchg(&msg->header.message_type, old_msg_type, 765e33f5211ab6 Michael Kelley 2019-05-30 @71 HVMSG_NONE) != old_msg_type) 765e33f5211ab6 Michael Kelley 2019-05-30 72 return; 765e33f5211ab6 Michael Kelley 2019-05-30 73 765e33f5211ab6 Michael Kelley 2019-05-30 74 /* 765e33f5211ab6 Michael Kelley 2019-05-30 75 * The cmxchg() above does an implicit memory barrier to 765e33f5211ab6 Michael Kelley 2019-05-30 76 * ensure the write to MessageType (ie set to 765e33f5211ab6 Michael Kelley 2019-05-30 77 * HVMSG_NONE) happens before we read the 765e33f5211ab6 Michael Kelley 2019-05-30 78 * MessagePending and EOMing. Otherwise, the EOMing 765e33f5211ab6 Michael Kelley 2019-05-30 79 * will not deliver any more messages since there is 765e33f5211ab6 Michael Kelley 2019-05-30 80 * no empty slot 765e33f5211ab6 Michael Kelley 2019-05-30 81 */ 765e33f5211ab6 Michael Kelley 2019-05-30 82 if (msg->header.message_flags.msg_pending) { 765e33f5211ab6 Michael Kelley 2019-05-30 83 /* 765e33f5211ab6 Michael Kelley 2019-05-30 84 * This will cause message queue rescan to 765e33f5211ab6 Michael Kelley 2019-05-30 85 * possibly deliver another msg from the 765e33f5211ab6 Michael Kelley 2019-05-30 86 * hypervisor 765e33f5211ab6 Michael Kelley 2019-05-30 87 */ 765e33f5211ab6 Michael Kelley 2019-05-30 @88 hv_signal_eom(); 765e33f5211ab6 Michael Kelley 2019-05-30 89 } 765e33f5211ab6 Michael Kelley 2019-05-30 90 } 765e33f5211ab6 Michael Kelley 2019-05-30 91 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org