Michael Kelley <mikelley@xxxxxxxxxxxxx> writes:
> As noted in a previous email, we don't have a consistent
> pattern for checking Hyper-V hypercall status. Existing code and
> recent new code uses a number of variants. The variants work, but
> a consistent pattern would improve the readability of the code, and
> be more conformant to what the Hyper-V TLFS says about hypercall
> status. In particular, the 64 bit hypercall status contains fields that
> the TLFS says should be ignored -- evidently they are not guaranteed
> to be zero (though I've never seen otherwise).
>
> I'd propose the following helper functions to go in
> asm-generic/mshyperv.h. The function names are relatively short
> for readability:
>
> static inline u64 hv_result(u64 status)
> {
> return status & HV_HYPERCALL_RESULT_MASK;
> }
>
> static inline bool hv_result_success(u64 status)
> {
> return hv_result(status) == HV_STATUS_SUCCESS;
> }
>
> static inline unsigned int hv_repcomp(u64 status)
> {
> return (status & HV_HYPERCALL_REP_COMP_MASK) >>
> HV_HYPERCALL_REP_COMP_OFFSET;
> }
>
> The hv_do_hypercall() function (and its 'rep' and 'fast' variants) should
> always assign the result to a u64 local variable, which is the return
> type of the functions. Then the above functions can act on that local
> variable. Here are some examples:
>
> u64 status;
> unsigned int completed;
>
> status = hv_do_hypercall(<some args>);
> if (!hv_result_success(status)) {
> <handle error case>
> }
>
> status = hv_do_rep_hypercall(<some args>);
> if (hv_result(status) == HV_STATUS_INSUFFICIENT_MEMORY) {
> <deposit more memory pages>
> goto retry;
> } else if (!hv_result_success(status)) {
> <handle error case>
> }
> completed = hv_repcomp(status);
>
>
> Thoughts?
Personally, I like it and think it's going to be sufficient.
Alternatively, I can suggest we introduce something like
struct hv_result {
u64 status:16;
u64 rsvd1:16;
u64 reps_comp:12;
u64 rsvd1:20;
};
and make hv_do_rep_hypercall() return it. So the code above will look
like:
struct hv_result result;
result = hv_do_rep_hypercall(<some args>);
if (result.status) == HV_STATUS_INSUFFICIENT_MEMORY) {
<deposit more memory pages>
goto retry;
} else if (result.status != HV_STATUS_SUCCESS) {
<handle error case>
}
completed = result.reps_comp;
--
Vitaly
