[PATCH] qemu: aspeed_timer: Use signed muldiv for timer resets

Christian Svensson bluecmd at google.com
Tue Nov 13 01:21:38 AEDT 2018

If the host decrements the counter register that results in a negative
delta. This is then passed to muldiv64 which only handles unsigned
numbers resulting in bogus results.

This fix ensures the data being operated on is signed before it is
ultimately casted to the final unsigned value.

Test case: kexec a kernel using aspeed_timer and it will freeze on the
second bootup when the kernel initializes the timer. With this patch
that no longer happens and the timer appears to run OK.

Signed-off-by: Christian Svensson <bluecmd at google.com>
 hw/timer/aspeed_timer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/timer/aspeed_timer.c b/hw/timer/aspeed_timer.c
index 9acd1de485..1a54d85e9d 100644
--- a/hw/timer/aspeed_timer.c
+++ b/hw/timer/aspeed_timer.c
@@ -253,7 +253,7 @@ static void aspeed_timer_set_value(AspeedTimerCtrlState *s, int timer, int reg,
             int64_t delta = (int64_t) value - (int64_t) calculate_ticks(t, now);
             uint32_t rate = calculate_rate(t);
-            t->start += muldiv64(delta, NANOSECONDS_PER_SECOND, rate);
+            t->start = (int64_t)t->start + ((__int128_t)delta * NANOSECONDS_PER_SECOND / rate);

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