The psci test performs a series of CPU_ON/CPU_OFF cycles for CPU 1. This is
done by setting the entry point for the CPU_ON call to the physical address
of the C function cpu_psci_cpu_die.
The compiler is well within its rights to use the stack when generating
code for cpu_psci_cpu_die. However, because no stack initialization has
been done, the stack pointer is zero, as set by KVM when creating the VCPU.
This causes a data abort without a change in exception level. The VBAR_EL1
register is also zero (the KVM reset value for VBAR_EL1), the MMU is off,
and we end up trying to fetch instructions from address 0x200.
At this point, a stage 2 instruction abort is generated which is taken to
KVM. KVM interprets this as an instruction fetch from an I/O region, and
injects a prefetch abort into the guest. Prefetch abort is a synchronous
exception, and on guest return the VCPU PC will be set to VBAR_EL1 + 0x200,
which is... 0x200. The VCPU ends up in an infinite loop causing a prefetch
abort while fetching the instruction to service the said abort.
To avoid all of this, lets use the assembly function halt as the CPU_ON
entry address. Also, expand the check to test that we only get
PSCI_RET_SUCCESS exactly once, as we're never offlining the CPU during the
test.
Signed-off-by: Alexandru Elisei <alexandru.elisei@xxxxxxx>
---
arm/psci.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/arm/psci.c b/arm/psci.c
index 5c1accb6cea4..ffc09a2e9858 100644
--- a/arm/psci.c
+++ b/arm/psci.c
@@ -79,13 +79,14 @@ static void cpu_on_secondary_entry(void)
cpumask_set_cpu(cpu, &cpu_on_ready);
while (!cpu_on_start)
cpu_relax();
- cpu_on_ret[cpu] = psci_cpu_on(cpus[1], __pa(cpu_psci_cpu_die));
+ cpu_on_ret[cpu] = psci_cpu_on(cpus[1], __pa(halt));
cpumask_set_cpu(cpu, &cpu_on_done);
}
static bool psci_cpu_on_test(void)
{
bool failed = false;
+ int ret_success = 0;
int cpu;
cpumask_set_cpu(1, &cpu_on_ready);
@@ -104,7 +105,7 @@ static bool psci_cpu_on_test(void)
cpu_on_start = 1;
smp_mb();
- cpu_on_ret[0] = psci_cpu_on(cpus[1], __pa(cpu_psci_cpu_die));
+ cpu_on_ret[0] = psci_cpu_on(cpus[1], __pa(halt));
cpumask_set_cpu(0, &cpu_on_done);
while (!cpumask_full(&cpu_on_done))
@@ -113,12 +114,19 @@ static bool psci_cpu_on_test(void)
for_each_present_cpu(cpu) {
if (cpu == 1)
continue;
- if (cpu_on_ret[cpu] != PSCI_RET_SUCCESS && cpu_on_ret[cpu] != PSCI_RET_ALREADY_ON) {
+ if (cpu_on_ret[cpu] == PSCI_RET_SUCCESS) {
+ ret_success++;
+ } else if (cpu_on_ret[cpu] != PSCI_RET_ALREADY_ON) {
report_info("unexpected cpu_on return value: caller=CPU%d, ret=%d", cpu, cpu_on_ret[cpu]);
failed = true;
}
}
+ if (ret_success != 1) {
+ report_info("got %d CPU_ON success", ret_success);
+ failed = true;
+ }
+
return !failed;
}
--
2.20.1
