On 22/06/2015 12:54, Alexander Spyridakis wrote:
Hello all,
You can find the latest tcg atomic test payload in the following repo:
> git clone https://git.virtualopensystems.com/dev/tcg_baremetal_tests.git
You also need an arm baremetal cross-compiler like arm-none-gnueabi-
(arm) and the usual aarch64-linux-gnu- (arm64). Due to a PSCI bug in
the current multithreading tcg repo, the atomic test was modified to
work also on the vexpress machine model.
To run it:
> make vexpress (or virt/virt64 for other targets)
> ../mttcg/arm-softmmu/qemu-system-arm -nographic -M vexpress-a15
-kernel build-vexpress/image-vexpress.axf -smp 4
On my machine it takes around 30 seconds for one run of the test and
the results vary from as low as 5 to 30 errors per vCPU per 10 million
iterations (no errors with KVM). It is also very interesting to note,
that the current test finishes faster on upstream qemu than
multithreaded qemu.
Best regards.
Hi,
I just tested this with vexpress, seems ATOMIC is not defined by default
it uses:
void non_atomic_lock(int *lock_var)
{
while (*lock_var != 0);
*lock_var = 1;
}
void non_atomic_unlock(int *lock_var)
{
*lock_var = 0;
}
instead of:
void atomic_lock(int *lock_var)
{
while (__sync_lock_test_and_set(lock_var, 1));
}
void atomic_unlock(int *lock_var)
{
__sync_lock_release(lock_var);
}
It doesn't cause any errors upstream but a lot on mttcg and mttcg is
faster in this
case.
I don't have any error when I use ATOMIC like this:
diff --git a/helpers.h b/helpers.h
index b5810ad..427659f 100644
--- a/helpers.h
+++ b/helpers.h
@@ -36,13 +36,8 @@
#define SYS_CFGCTR_WRITE 0x40000000
#define SYS_CFG_SHUTDOWN 0x00800000
-#ifdef ATOMIC
#define LOCK atomic_lock
#define UNLOCK atomic_unlock
-#else
-#define LOCK non_atomic_lock
-#define UNLOCK non_atomic_unlock
-#endif
int online_cpus;
int global_lock;
but it's slower than upstream which I think is normal. We can have two CPUs
fighting for the lock in mttcg but not in upstream as VCPUs doesn't run
at the same
time.
Fred
