Messages in this thread | | | Date | Thu, 16 Mar 2023 10:59:39 +0100 | Subject | Re: [PATCH v3 6/8] platform/x86/intel/ifs: Implement Array BIST test | From | Hans de Goede <> |
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Hi,
On 3/13/23 17:37, Joseph, Jithu wrote: > Hans, > > Thank-you very much for the review. > > On 3/13/2023 9:24 AM, Hans de Goede wrote: > > >>> >>> +#define SPINUNIT 100 /* 100 nsec */ >>> +static atomic_t array_cpus_out; >> >> This variable is only inc-ed + read, it is never reset to 0 >> so the "while (atomic_read(t) < all_cpus)" >> check only works for the first test run. >> > > It is reset to zero as annotated below. Let me know if this doesn't address your concern.
Ah, I somehow missed that despite looking for it twice, yes that is fine.
>> Also even static atomic_t variables must be initialized, you cannot >> assume that using using zeroed mem is a valid value for an atomic_t. >> >> And this is also shared between all smt pairs, so if 2 "real" >> CPU cores with both 2 sibblings are asked to run IFS tests at >> the same time, then array_cpus_out will get increased 4 times >> in total, breaking the wait_for_sibbling loop as soon as >> the counter reaches 2, so before the tests are done. > > Only one IFS test is allowed at a time. This is done using "ifs_sem" defined in sysfs.c
Ah I see.
After taking a closer look I do see one unrelated issue with this patch sysfs.c: run_test_store() does:
if (!ifsd->loaded) rc = -EPERM; else rc = do_core_test(cpu, dev);
But AFAICT the loaded check really only applies to the first (intel_ifs_0 device) test type and the Array BIST test should work fine when loaded is false.
So I think that the if (!ifsd->loaded) error check should be moved to ifs_test_core() ?
Regards,
Hans
> > ... > >>> +static void ifs_array_test_core(int cpu, struct device *dev) >>> +{ >>> + union ifs_array command = {}; >>> + bool timed_out = false; >>> + struct ifs_data *ifsd; >>> + unsigned long timeout; >>> + >>> + ifsd = ifs_get_data(dev); >>> + >>> + command.array_bitmask = ~0U; >>> + timeout = jiffies + HZ / 2; >>> + >>> + do { >>> + if (time_after(jiffies, timeout)) { >>> + timed_out = true; >>> + break; >>> + } >>> + atomic_set(&array_cpus_out, 0); > > The above line is where the zero initialization happens before every test. > >>> + stop_core_cpuslocked(cpu, do_array_test, &command); >>> + >>> + if (command.ctrl_result) >>> + break; >>> + } while (command.array_bitmask); >>> + >>> + ifsd->scan_details = command.data; >>> + >>> + if (command.ctrl_result) >>> + ifsd->status = SCAN_TEST_FAIL; >>> + else if (timed_out || command.array_bitmask) >>> + ifsd->status = SCAN_NOT_TESTED; >>> + else >>> + ifsd->status = SCAN_TEST_PASS; >>> +} > > Jithu >
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