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hpet: avoid timer storms on periodic timers 

If the period is set to a value that is too low, there could be no
time left to run the rest of QEMU.  Do not trigger interrupts faster
than 1 MHz.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2024-07-16 12:35:39 +02:00
parent 242d665396
commit 7c912ffb59
1 changed files with 11 additions and 2 deletions
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13
hw/timer/hpet.c
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@ -59,6 +59,7 @@ typedef struct HPETTimer { /* timers */
uint8_t wrap_flag; /* timer pop will indicate wrap for one-shot 32-bit
* mode. Next pop will be actual timer expiration.
*/
uint64_t last; /* last value armed, to avoid timer storms */
} HPETTimer;
struct HPETState {
@ -266,6 +267,7 @@ static int hpet_post_load(void *opaque, int version_id)
for (i = 0; i < s->num_timers; i++) {
HPETTimer *t = &s->timer[i];
t->cmp64 = hpet_calculate_cmp64(t, s->hpet_counter, t->cmp);
t->last = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - NANOSECONDS_PER_SECOND;
}
/* Recalculate the offset between the main counter and guest time */
if (!s->hpet_offset_saved) {
@ -364,8 +366,15 @@ static const VMStateDescription vmstate_hpet = {
static void hpet_arm(HPETTimer *t, uint64_t tick)
{
/* FIXME: Clamp period to reasonable min value? */
timer_mod(t->qemu_timer, hpet_get_ns(t->state, tick));
uint64_t ns = hpet_get_ns(t->state, tick);
/* Clamp period to reasonable min value (1 us) */
if (timer_is_periodic(t) && ns - t->last < 1000) {
ns = t->last + 1000;
}
t->last = ns;
timer_mod(t->qemu_timer, ns);
}
/*