[kbuild-all] Re: [PATCH] x86/entry/64: Disallow RDPID in paranoid entry if KVM is enabled

Hi Sean, I love your patch! Yet something to improve: [auto build test ERROR on tip/auto-latest] [also build test ERROR on v5.9-rc1 next-20200821] [cannot apply to tip/x86/asm luto/next] [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/Sean-Christopherson/x86-entry-64... base: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git a9bd3a91d6e49ebd2d7d8ace91d4cc339c382a31 config: x86_64-randconfig-s022-20200821 (attached as .config) compiler: gcc-9 (Debian 9.3.0-15) 9.3.0 reproduce: # apt-get install sparse # sparse version: v0.6.2-191-g10164920-dirty # save the attached .config to linux build tree make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=x86_64 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 >>): arch/x86/entry/entry_64.S: Assembler messages: # https://github.com/0day-ci/linux/commit/bebb51882f9c18938e44b6a7b66fdf045... git remote add linux-review https://github.com/0day-ci/linux git fetch --no-tags linux-review Sean-Christopherson/x86-entry-64-Disallow-RDPID-in-paranoid-entry-if-KVM-is-enabled/20200821-105339 git checkout bebb51882f9c18938e44b6a7b66fdf0452eea142 vim +851 arch/x86/entry/entry_64.S 794 795 /* 796 * Save all registers in pt_regs. Return GSBASE related information 797 * in EBX depending on the availability of the FSGSBASE instructions: 798 * 799 * FSGSBASE R/EBX 800 * N 0 -> SWAPGS on exit 801 * 1 -> no SWAPGS on exit 802 * 803 * Y GSBASE value at entry, must be restored in paranoid_exit 804 */ 805 SYM_CODE_START_LOCAL(paranoid_entry) 806 UNWIND_HINT_FUNC 807 cld 808 PUSH_AND_CLEAR_REGS save_ret=1 809 ENCODE_FRAME_POINTER 8 810 811 /* 812 * Always stash CR3 in %r14. This value will be restored, 813 * verbatim, at exit. Needed if paranoid_entry interrupted 814 * another entry that already switched to the user CR3 value 815 * but has not yet returned to userspace. 816 * 817 * This is also why CS (stashed in the "iret frame" by the 818 * hardware at entry) can not be used: this may be a return 819 * to kernel code, but with a user CR3 value. 820 * 821 * Switching CR3 does not depend on kernel GSBASE so it can 822 * be done before switching to the kernel GSBASE. This is 823 * required for FSGSBASE because the kernel GSBASE has to 824 * be retrieved from a kernel internal table. 825 */ 826 SAVE_AND_SWITCH_TO_KERNEL_CR3 scratch_reg=%rax save_reg=%r14 827 828 /* 829 * Handling GSBASE depends on the availability of FSGSBASE. 830 * 831 * Without FSGSBASE the kernel enforces that negative GSBASE 832 * values indicate kernel GSBASE. With FSGSBASE no assumptions 833 * can be made about the GSBASE value when entering from user 834 * space. 835 */ 836 ALTERNATIVE "jmp .Lparanoid_entry_checkgs", "", X86_FEATURE_FSGSBASE 837 838 /* 839 * Read the current GSBASE and store it in %rbx unconditionally, 840 * retrieve and set the current CPUs kernel GSBASE. The stored value 841 * has to be restored in paranoid_exit unconditionally. 842 * 843 * The MSR write ensures that no subsequent load is based on a 844 * mispredicted GSBASE. No extra FENCE required. 845 * 846 * Disallow RDPID if KVM is enabled as it may consume a guest's TSC_AUX 847 * if an NMI arrives in KVM's run loop. KVM loads guest's TSC_AUX on 848 * VM-Enter and may not restore the host's value until the CPU returns 849 * to userspace, i.e. KVM depends on the kernel not using TSC_AUX. 850 */ 852 ret 853 --- 0-DAY CI Kernel Test Service, Intel Corporation https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org