Re: [Xen-devel] [PATCH v2] x86/HVM: change the flags cpu context field to uint64_t

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.01.16 at 16:38, <roger.pau@xxxxxxxxxx> wrote:
> El 18/01/16 a les 16.24, Andrew Cooper ha escrit:
>> On 18/01/16 15:21, Jan Beulich wrote:
>>>>>> On 18.01.16 at 16:09, <roger.pau@xxxxxxxxxx> wrote:
>>>> --- a/xen/include/public/arch-x86/hvm/save.h
>>>> +++ b/xen/include/public/arch-x86/hvm/save.h
>>>> @@ -161,8 +161,8 @@ struct hvm_hw_cpu {
>>>>      uint32_t error_code;
>>>>  
>>>>  #define _XEN_X86_FPU_INITIALISED        0
>>>> -#define XEN_X86_FPU_INITIALISED         (1U<<_XEN_X86_FPU_INITIALISED)
>>>> -    uint32_t flags;
>>>> +#define XEN_X86_FPU_INITIALISED         (1UL<<_XEN_X86_FPU_INITIALISED)
>>>> +    uint64_t flags;
>>>>  };
>>> How is the UL going to make this safe for a 32-bit consumer?
>>> Makes me think that, other than just said in reply to v1, it'll
>>> indeed be better to have a separate field (with a separate
>>> zero-check)... The (undesirable imo) alternative being to use
>>> 1L instead.
>> 
>> I am happy either way.  My R-b stands.
> 
> What about using ULL or simply casting to uint64_t?

ULL might not be supported by pre-C99 compilers. Casting to
uint64_t is, well, ugly. The flags field really has no business
being wider then 32 bits.

Jan


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