GIC 3.0's SGI interrupt latency seems much bigger than GIC 2.0

Hi,

I tested SGI interrupt latency, it seems that GIC3.0's SGI interrupt latency are much bigger than GIC2.0.

How to test:

GIC3.0:

1. read timestamp(t01)

2. core0 write  ICC_SGI0R_EL1 to trigger core1, read timestamp(t02)

3. isr in core1, read timestamp(t03)

GIC2.0:

1. read timestamp(t11)

2. core0 write GICD_SGIR to trigger core1, read timestamp(t12)

3. isr in core1, read timestamp(t13)

Result is (had think about the time of reading timestamp):

1. (t02 - t01)  nearly 3 times bigger than (t12 - t11)  which means system register cost more time than access to memory mapped memory.

2. (t03 - t02) nearly 2 times bigger than (t13 - t12) which means interrupt latency of GIC3.0 are much bigger than GIC 2.0

Is this normal? Any help will be appreciated! Thanks!

BR,

Peng