Re: [PATCH] kvm: x86: hyperv: delete dead code in kvm_hv_hypercall()

Paolo Bonzini
2018-03-19T16:01:27Z

On 17/03/2018 16:11, Liran Alon wrote:
>
>> "rep_done" is always zero so the "(((u64)rep_done & 0xfff) << 32)"
>> expression is just zero. We can remove the "res" temporary variable
>> as
>> well and just use "ret" directly.
>>
>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>
> I think this commit should better be dropped than applied.
> The original code makes sense.
> It will make it easier to implement an hyper-v rep hypercall (which require rep_done).
> I don't think it makes current code much more complicated than it is without it.

If we really want to be ready for rep hypercalls, it would be better to
have a macro

#define HVCALL_MAKE_RESULT(retcode, rep_done)

and call it with a constant 0 as the second argument. A variable that
is never written except in the initializer is only adding noise.

Paolo