Re: linux-next: Tree for Mar 25 (arch/x86/kvm/)

[Randy Dunlap]

On 3/25/20 8:46 AM, Paolo Bonzini wrote:
> On 25/03/20 16:30, Randy Dunlap wrote:
>> 24 (only showing one of them here) BUILD_BUG() errors in arch/x86/kvm/cpuid.h
>> function __cpuid_entry_get_reg(), for the default: case.
>>
>>
>>   CC      arch/x86/kvm/cpuid.o
>> In file included from ../include/linux/export.h:43:0,
>>                  from ../include/linux/linkage.h:7,
>>                  from ../include/linux/preempt.h:10,
>>                  from ../include/linux/hardirq.h:5,
>>                  from ../include/linux/kvm_host.h:7,
>>                  from ../arch/x86/kvm/cpuid.c:12:
>> In function â__cpuid_entry_get_regâ,
>>     inlined from âkvm_cpu_cap_maskâ at ../arch/x86/kvm/cpuid.c:272:25,
>>     inlined from âkvm_set_cpu_capsâ at ../arch/x86/kvm/cpuid.c:292:2:
>> ../include/linux/compiler.h:394:38: error: call to â__compiletime_assert_114â declared with attribute error: BUILD_BUG failed
>>   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>>                                       ^
>> ../include/linux/compiler.h:375:4: note: in definition of macro â__compiletime_assertâ
>>     prefix ## suffix();    \
>>     ^~~~~~
>> ../include/linux/compiler.h:394:2: note: in expansion of macro â_compiletime_assertâ
>>   _compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
>>   ^~~~~~~~~~~~~~~~~~~
>> ../include/linux/build_bug.h:39:37: note: in expansion of macro âcompiletime_assertâ
>>  #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
>>                                      ^~~~~~~~~~~~~~~~~~
>> ../include/linux/build_bug.h:59:21: note: in expansion of macro âBUILD_BUG_ON_MSGâ
>>  #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
>>                      ^~~~~~~~~~~~~~~~
>> ../arch/x86/kvm/cpuid.h:114:3: note: in expansion of macro âBUILD_BUGâ
>>    BUILD_BUG();
>>    ^~~~~~~~~
>>
> 
> Looks like the compiler is not smart enough to figure out the constant 
> expressions in BUILD_BUG.  I think we need to do something like this:
> 
> diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> index 23b4cd1ad986..8f711b0cdec0 100644
> --- a/arch/x86/kvm/cpuid.h
> +++ b/arch/x86/kvm/cpuid.h
> @@ -40,6 +40,7 @@ struct cpuid_reg {
>  	int reg;
>  };
>  
> +/* Update reverse_cpuid_check as well when adding an entry.  */
>  static const struct cpuid_reg reverse_cpuid[] = {
>  	[CPUID_1_EDX]         = {         1, 0, CPUID_EDX},
>  	[CPUID_8000_0001_EDX] = {0x80000001, 0, CPUID_EDX},
> @@ -68,12 +69,21 @@ static const struct cpuid_reg reverse_cpuid[] = {
>   */
>  static __always_inline void reverse_cpuid_check(unsigned int x86_leaf)
>  {
> -	BUILD_BUG_ON(x86_leaf == CPUID_LNX_1);
> -	BUILD_BUG_ON(x86_leaf == CPUID_LNX_2);
> -	BUILD_BUG_ON(x86_leaf == CPUID_LNX_3);
> -	BUILD_BUG_ON(x86_leaf == CPUID_LNX_4);
> -	BUILD_BUG_ON(x86_leaf >= ARRAY_SIZE(reverse_cpuid));
> -	BUILD_BUG_ON(reverse_cpuid[x86_leaf].function == 0);
> +	BUILD_BUG_ON(x86_leaf != CPUID_1_EDX &&
> +	             x86_leaf != CPUID_8000_0001_EDX &&
> +	             x86_leaf != CPUID_8086_0001_EDX &&
> +	             x86_leaf != CPUID_1_ECX &&
> +	             x86_leaf != CPUID_C000_0001_EDX &&
> +	             x86_leaf != CPUID_8000_0001_ECX &&
> +	             x86_leaf != CPUID_7_0_EBX &&
> +	             x86_leaf != CPUID_D_1_EAX &&
> +	             x86_leaf != CPUID_8000_0008_EBX &&
> +	             x86_leaf != CPUID_6_EAX &&
> +	             x86_leaf != CPUID_8000_000A_EDX &&
> +	             x86_leaf != CPUID_7_ECX &&
> +	             x86_leaf != CPUID_8000_0007_EBX &&
> +	             x86_leaf != CPUID_7_EDX &&
> +	             x86_leaf != CPUID_7_1_EAX);
>  }
>  
>  /*
> 
> Randy, can you test it with your compiler?

Nope, no help.  That's the wrong location.
Need a patch for this:
>> 24 (only showing one of them here) BUILD_BUG() errors in arch/x86/kvm/cpuid.h
>> function __cpuid_entry_get_reg(), for the default: case.


-- 
~Randy