+Andrew
On Fri, Feb 21, 2025, Su Hui wrote:
> When build kernel with randconfig, there is an error:
>
> In function ‘kvm_is_cr4_bit_set’,inlined from
> ‘kvm_update_cpuid_runtime’ at arch/x86/kvm/cpuid.c:310:9:
>
> include/linux/compiler_types.h:542:38: error: call to
> ‘__compiletime_assert_380’ declared with attribute error:
> BUILD_BUG_ON failed: !is_power_of_2(cr4_bit).
Andrew, do you want to grab this? Looks like you've taken the last few changes
to log2.h, and KVM isn't the only subsystem that expects is_power_of_2() to yield
a compile-time constant; taking this through the KVM tree feels wrong.
arch/x86/kvm/kvm_cache_regs.h: BUILD_BUG_ON(!is_power_of_2(cr0_bit));
arch/x86/kvm/kvm_cache_regs.h: BUILD_BUG_ON(!is_power_of_2(cr4_bit));
arch/x86/kvm/x86.c: BUILD_BUG_ON(!is_power_of_2(ASYNC_PF_PER_VCPU));
drivers/net/ipa/gsi.c: BUILD_BUG_ON(!is_power_of_2(GSI_RING_ELEMENT_SIZE));
drivers/vfio/pci/virtio/legacy_io.c: BUILD_BUG_ON(!is_power_of_2(virtvdev->bar0_virtual_buf_size));
kernel/kcov.c: BUILD_BUG_ON(!is_power_of_2(KCOV_WORDS_PER_CMP));
mm/sparse.c: BUILD_BUG_ON(!is_power_of_2(sizeof(struct mem_section)));
mm/swap_cgroup.c: BUILD_BUG_ON(!is_power_of_2(ID_PER_SC));
> '!is_power_of_2(X86_CR4_OSXSAVE)' is False, but gcc treats is_power_of_2()
> as non-inline function and a compilation error happens. Fix this by marking
> is_power_of_2() with __always_inline.
>
> Signed-off-by: Su Hui <suhui@xxxxxxxxxxxx>
> ---
> include/linux/log2.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/log2.h b/include/linux/log2.h
> index 9f30d087a128..1366cb688a6d 100644
> --- a/include/linux/log2.h
> +++ b/include/linux/log2.h
> @@ -41,7 +41,7 @@ int __ilog2_u64(u64 n)
> * *not* considered a power of two.
> * Return: true if @n is a power of 2, otherwise false.
> */
> -static inline __attribute__((const))
> +static __always_inline __attribute__((const))
> bool is_power_of_2(unsigned long n)
> {
> return (n != 0 && ((n & (n - 1)) == 0));
> --
> 2.30.2
>
