arch_timer_edge_cases failures on ampere-one

[Sebastian Ott <sebott@redhat.com>]

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?

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?

Sebastian