On 22/04/2021 16:07, Sean Christopherson wrote:
> On Thu, Apr 22, 2021, Colin King wrote:
>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>
>> Currently entry->ebx is being zero'd by masking itself with zero.
>> Simplify this by just assigning zero, cleans up static analysis
>> warning.
>>
>> Addresses-Coverity: ("Bitwise-and with zero")
>> Signed-off-by: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>> ---
>> arch/x86/kvm/cpuid.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>> index 57744a5d1bc2..9bcc2ff4b232 100644
>> --- a/arch/x86/kvm/cpuid.c
>> +++ b/arch/x86/kvm/cpuid.c
>> @@ -851,7 +851,7 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
>> entry->eax &= SGX_ATTR_DEBUG | SGX_ATTR_MODE64BIT |
>> SGX_ATTR_PROVISIONKEY | SGX_ATTR_EINITTOKENKEY |
>> SGX_ATTR_KSS;
>> - entry->ebx &= 0;
>> + entry->ebx = 0;
>
> I 100% understand the code is funky, but using &= is intentional. ebx:eax holds
> a 64-bit value that is a effectively a set of feature flags. While the upper
> 32 bits are extremely unlikely to be used any time soon, if a feature comes
> along then the correct behavior would be:
>
> entry->ebx &= SGX_ATTR_FANCY_NEW_FEATURE;
>
> While directly setting entry->ebx would be incorrect. The idea is to set up a
> future developer for success so that they don't forget to add the "&".
>
> TL;DR: I'd prefer to keep this as is, even though it's rather ridiculous.
OK, makes sense. Thanks for explaining.
>
>> break;
>> /* Intel PT */
>> case 0x14:
>> --
>> 2.30.2
>>
