Messages in this thread | | | Date | Wed, 25 Apr 2018 09:16:53 -0700 (PDT) | Subject | Re: [PATCH v5 0/2] perf: riscv: Preliminary Perf Event Support on RISC-V | From | Palmer Dabbelt <> |
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On Tue, 24 Apr 2018 18:15:49 PDT (-0700), atish.patra@wdc.com wrote: > On 4/24/18 5:29 PM, Palmer Dabbelt wrote: >> On Tue, 24 Apr 2018 15:16:16 PDT (-0700), atish.patra@wdc.com wrote: >>> On 4/24/18 12:44 PM, Palmer Dabbelt wrote: >>>> On Tue, 24 Apr 2018 12:27:26 PDT (-0700), atish.patra@wdc.com wrote: >>>>> On 4/24/18 11:07 AM, Atish Patra wrote: >>>>>> On 4/19/18 4:28 PM, Alan Kao wrote: >>>>>> However, I got an rcu-stall for the test "47: Event times". >>>>>> # ./perf test -v 47 >>>>> Got it working. The test tries to attach the event to CPU0 which doesn't >>>>> exist in HighFive Unleashed. Changing it to cpu1 works. >>>>> >>>>> diff --git a/tools/perf/tests/event-times.c b/tools/perf/tests/event-times.c >>>>> index 1a2686f..eb11632f 100644 >>>>> --- a/tools/perf/tests/event-times.c >>>>> +++ b/tools/perf/tests/event-times.c >>>>> @@ -113,9 +113,9 @@ static int attach__cpu_disabled(struct perf_evlist >>>>> *evlist) >>>>> struct cpu_map *cpus; >>>>> int err; >>>>> >>>>> - pr_debug("attaching to CPU 0 as enabled\n"); >>>>> + pr_debug("attaching to CPU 1 as disabled\n"); >>>>> >>>>> - cpus = cpu_map__new("0"); >>>>> + cpus = cpu_map__new("1"); >>>>> if (cpus == NULL) { >>>>> pr_debug("failed to call cpu_map__new\n"); >>>>> return -1; >>>>> @@ -142,9 +142,9 @@ static int attach__cpu_enabled(struct perf_evlist >>>>> *evlist) >>>>> struct cpu_map *cpus; >>>>> int err; >>>>> >>>>> - pr_debug("attaching to CPU 0 as enabled\n"); >>>>> + pr_debug("attaching to CPU 1 as enabled\n"); >>>>> >>>>> - cpus = cpu_map__new("0"); >>>>> + cpus = cpu_map__new("1"); >>>>> if (cpus == NULL) { >>>>> pr_debug("failed to call cpu_map__new\n"); >>>>> return -1; >>>>> >>>>> >>>>> Palmer, >>>>> Would it be better to officially document it somewhere that CPU0 doesn't >>>>> exist in the HighFive Unleashed board ? >>>>> I fear that there will be other standard tests/code path that may fail >>>>> because of inherent assumption of cpu0 presence. >>>> >>>> I think the best way to fix this is to just have BBL (or whatever the >>>> bootloader is) renumber the CPUs so they're contiguous and begin with 0. >>> >>> Do you mean BBL will update the device tree that kernel eventually parse >>> and set the hart id? >>> Sounds good to me unless it acts as a big hack in future boot loaders. >> >> Right now the machine-mode and supervisor-mode hart IDs are logically separate: >> the bootloader just provides the hart ID as a register argument when starting >> the kernel. > > Yes. > > BBL already needs to enumerate the harts by looking through the >> device tree for various other reasons (at least to mask off the harts that >> Linux doesn't support), so it's not that much effort to just maintain a mapping >> from supervisor-mode hart IDs to machine-mode hart IDs. >> > > But Linux also parses the device tree to get hart ID in > riscv_of_processor_hart(). This is used to setup the possible/present > cpu map in setup_smp(). > > Thus, Linux also need to see a device tree with cpu0-3 instead of > cpu1-4. Otherwise, present cpu map will be incorrect. Isn't it ? > >> I have some patches floating around that do this, but appear to do it >> incorrectly enough that nothing boots so maybe I'm missing something that makes >> this complicated :). >> > > Just a wild guess: May be the because of the above reason ;)
I was already changing all the IDs in the device tree, so that wasn't it.
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