Messages in this thread | | | Subject | Re: [PATCH v3 15/21] x86/resctrl: Abstract __rmid_read() | From | James Morse <> | Date | Wed, 30 Mar 2022 17:44:29 +0100 |
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Hi Reinette,
On 16/03/2022 21:52, Reinette Chatre wrote: > On 2/17/2022 10:21 AM, James Morse wrote: >> __rmid_read() selects the specified eventid and returns the counter >> value from the MSR. The error handling is architecture specific, and >> handled by the callers, rdtgroup_mondata_show() and __mon_event_count(). >> >> Error handling should be handled by architecture specific code, as >> a different architecture may have different requirements. MPAM's >> counters can report that they are 'not ready', requiring a second >> read after a short delay. This should be hidden from resctrl. >> >> Make __rmid_read() the architecture specific function for reading >> a counter. Rename it resctrl_arch_rmid_read() and move the error >> handling into it.
>> @@ -180,14 +180,24 @@ static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid) >> * are error bits. >> */ >> wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid); >> - rdmsrl(MSR_IA32_QM_CTR, val); >> + rdmsrl(MSR_IA32_QM_CTR, msr_val); >> >> - return val; >> + if (msr_val & RMID_VAL_ERROR) >> + return -EIO; >> + if (msr_val & RMID_VAL_UNAVAIL) >> + return -EINVAL; >> + >> + *val = msr_val; >> + >> + return 0; >> } > > From above we see that resctrl_arch_rmid_read() returns an int that could be > -EIO or -EINVAL ... > > ... > >> @@ -319,15 +331,15 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr) >> { >> struct rdt_hw_resource *hw_res = resctrl_to_arch_res(rr->r); >> struct mbm_state *m; >> - u64 chunks, tval; >> + u64 chunks, tval = 0; >> >> if (rr->first) >> resctrl_arch_reset_rmid(rr->r, rr->d, rmid, rr->evtid); >> >> - tval = __rmid_read(rmid, rr->evtid); >> - if (tval & (RMID_VAL_ERROR | RMID_VAL_UNAVAIL)) { >> - return tval; >> - } >> + rr->err = resctrl_arch_rmid_read(rmid, rr->evtid, &tval); >> + if (rr->err) >> + return rr->err; >> + > > Setting rr->err, an int, to the return of resctrl_arch_rmid_read() is ok and > can handle the negative error codes, but returning it here means that > __mon_event_count()'s return type should be changed, > it is currently u64.
Good point. Fixed.
>> @@ -419,9 +431,14 @@ void mon_event_count(void *info) >> } >> } >> > > Also take care here ... ret_val in mon_event_count() is still u64 while > __mon_event_count() attempts to return negative errors.
(yup, fixed)
>> - /* Report error if none of rmid_reads are successful */ >> - if (ret_val) >> - rr->val = ret_val; >> + /* >> + * __mon_event_count() calls for newly created monitor groups may >> + * report -EINVAL/Unavailable if the monitor hasn't seen any traffic. >> + * If the first call for the control group succeed, discard any error >> + * set by reads of monitor groups. >> + */ > > Additionally, if the first call fails, but a following read of monitor group > succeeds then the first call's error is discarded. > > How about if the last sentence is replaced with: > "Discard error if any of the monitor event reads succeeded."
Sure,
Thanks,
James
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