On Thu, 10 Apr 2025 16:10:43 +0100, Sebastian Ott <sebott@xxxxxxxxxx> wrote: > > Hey, > > I'm seeing consistent failures for the arch_timer_edge_cases > selftest one ampere-one(x): > ==== Test Assertion Failure ==== > arm64/arch_timer_edge_cases.c:170: timer_condition == istatus > pid=6277 tid=6277 errno=4 - Interrupted system call > 1 0x0000000000403bcf: test_run at arch_timer_edge_cases.c:962 > 2 0x0000000000401f1f: main at arch_timer_edge_cases.c:1083 > 3 0x0000ffffa8b2625b: ?? ??:0 > 4 0x0000ffffa8b2633b: ?? ??:0 > 5 0x000000000040202f: _start at ??:? > 0x1 != 0x0 (timer_condition != istatus) > > The (first) test that's failing is from test_timers_in_the_past(): > /* Set a timer to counter=0 (in the past) */ > test_timer_cval(timer, 0, wm, true, DEF_CNT); > > If I understand this correctly then the timer condition is met, an > irq should be raised with the istatus bit from SYS_CNTV_CTL_EL0 set. > > What the guest gets for SYS_CNTV_CTL_EL0 is 1 (only the enable bit > set). KVM also reads 1 in timer_save_state() via > read_sysreg_el0(SYS_CNTV_CTL). Is this a HW/FW issue? My hunch is that this is related to AC03_CPU_14 in [1] (now archived locally for future reference...). > > These machines have FEAT_ECV (as a test I disabled that in the kernel > but with the same result). > > As a hack I set ARCH_TIMER_CTRL_IT_STAT in timer_save_state() when > the timer condition is met and set up traps for the register - this > lets the testcase succeed. > > All with the current upstream kernel - but this is not new, I saw > this a couple of months ago but lost access to the machine before > I could debug.. > > Any hints what to do here? Not a lot to do, assuming this is the actual cause. Similar things happen on my QC box, which has a "remarkable" timer implementation and a bunch of terrible hacks to keep it alive. On the other hand, I'm not even convinced that this test-case is legit. It seems to rely on the counter being 64bit wide, which is not always the case. M. [1] https://amperecomputing.com/assets/AmpereOne_Developer_ER_v0_80_20240823_28945022f4.pdf -- Without deviation from the norm, progress is not possible.
