Hello Nick,
On 7/26/23 20:22, Nicholas Piggin wrote:
When writing a value to the decrementer that raises an exception, the
irq is raised, but the value is not stored so the store doesn't appear
to have changed the register when it is read again.
Always store the write value to the register.
This change has a serious performance impact when a guest is run under
PowerNV. Could you please take a look ?
Thanks,
C.
PS: We should really introduce avocado tests for nested.
Fixes: e81a982aa53 ("PPC: Clean up DECR implementation")
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
hw/ppc/ppc.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index fa60f76dd4..cd1993e9c1 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -812,6 +812,11 @@ static void __cpu_ppc_store_decr(PowerPCCPU *cpu, uint64_t
*nextp,
return;
}
+ /* Calculate the next timer event */
+ now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
+ next = muldiv64(now, tb_env->decr_freq, NANOSECONDS_PER_SECOND) + value;
+ *nextp = next; /* nextp is in timebase units */
+
/*
* Going from 1 -> 0 or 0 -> -1 is the event to generate a DEC interrupt.
*
@@ -833,11 +838,6 @@ static void __cpu_ppc_store_decr(PowerPCCPU *cpu, uint64_t
*nextp,
(*lower_excp)(cpu);
}
- /* Calculate the next timer event */
- now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
- next = muldiv64(now, tb_env->decr_freq, NANOSECONDS_PER_SECOND) + value;
- *nextp = next; /* nextp is in timebase units */
-
/* Adjust timer */
timer_mod(timer, muldiv64(next, NANOSECONDS_PER_SECOND,
tb_env->decr_freq));
}
