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    SubjectRe: selftests: resctrl: cat_test.c: In function 'noncont_cat_run_test': ../kselftest.h:74:9: error: impossible constraint in 'asm' 74 | __asm__ __volatile__ ("cpuid\n\t"
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    On 4/18/2024 2:37 AM, Naresh Kamboju wrote:
    > The Linux next building selftests with gcc-13 found these build warnings
    > and errors.
    >
    > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
    >
    > Build log:
    > ---------
    > Path:
    > selftests/resctrl/resctrl_tests/
    >
    > In file included from resctrl.h:24,
    > from cat_test.c:11:
    > cat_test.c: In function 'noncont_cat_run_test':
    > ../kselftest.h:74:9: error: impossible constraint in 'asm'
    > 74 | __asm__ __volatile__ ("cpuid\n\t"
    > \
    > | ^~~~~~~
    > cat_test.c:308:17: note: in expansion of macro '__cpuid_count'
    > 308 | __cpuid_count(0x10, 1, eax, ebx, ecx, edx);
    > | ^~~~~~~~~~~~~
    > ../kselftest.h:74:9: error: impossible constraint in 'asm'
    > 74 | __asm__ __volatile__ ("cpuid\n\t"
    > \
    > | ^~~~~~~
    > cat_test.c:310:17: note: in expansion of macro '__cpuid_count'
    > 310 | __cpuid_count(0x10, 2, eax, ebx, ecx, edx);
    > | ^~~~~~~~~~~~~
    >

    This is unexpected to me. kselftest.h intends to and still does define
    __cpuid_count() exactly the same as gcc does (in gcc/config/i386/cpuid.h):


    255 #define __cpuid_count(level, count, a, b, c, d) \
    256 __asm__ __volatile__ ("cpuid\n\t" \
    257 : "=a" (a), "=b" (b), "=c" (c), "=d" (d) \
    258 : "0" (level), "2" (count))

    Reinette

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