2008-01-28 04:10:22 +07:00
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#ifndef __I8254_H
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#define __I8254_H
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2012-04-24 21:40:17 +07:00
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#include <linux/kthread.h>
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2015-03-26 21:39:29 +07:00
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#include <kvm/iodev.h>
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2008-01-28 04:10:22 +07:00
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struct kvm_kpit_channel_state {
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u32 count; /* can be 65536 */
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u16 latched_count;
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u8 count_latched;
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u8 status_latched;
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u8 status;
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u8 read_state;
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u8 write_state;
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u8 write_latch;
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u8 rw_mode;
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u8 mode;
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u8 bcd; /* not supported */
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u8 gate; /* timer start */
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ktime_t count_load_time;
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};
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struct kvm_kpit_state {
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2016-03-03 04:56:44 +07:00
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/* All members before "struct mutex lock" are protected by the lock. */
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2008-01-28 04:10:22 +07:00
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struct kvm_kpit_channel_state channels[3];
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2009-07-07 22:50:38 +07:00
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u32 flags;
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2009-02-23 20:57:41 +07:00
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bool is_periodic;
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2012-07-26 22:01:53 +07:00
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s64 period; /* unit: ns */
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struct hrtimer timer;
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2008-01-28 04:10:22 +07:00
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u32 speaker_data_on;
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2016-03-03 04:56:44 +07:00
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2008-01-28 04:10:22 +07:00
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struct mutex lock;
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2016-03-03 04:56:52 +07:00
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atomic_t reinject;
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2016-03-03 04:56:44 +07:00
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atomic_t pending; /* accumulated triggered timers */
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KVM: i8254: use atomic_t instead of pit.inject_lock
The lock was an overkill, the same can be done with atomics.
A mb() was added in kvm_pit_ack_irq, to pair with implicit barrier
between pit_timer_fn and pit_do_work. The mb() prevents a race that
could happen if pending == 0 and irq_ack == 0:
kvm_pit_ack_irq: | pit_timer_fn:
p = atomic_read(&ps->pending); |
| atomic_inc(&ps->pending);
| queue_work(pit_do_work);
| pit_do_work:
| atomic_xchg(&ps->irq_ack, 0);
| return;
atomic_set(&ps->irq_ack, 1); |
if (p == 0) return; |
where the interrupt would not be delivered in this tick of pit_timer_fn.
PIT would have eventually delivered the interrupt, but we sacrifice
perofmance to make sure that interrupts are not needlessly delayed.
sfence isn't enough: atomic_dec_if_positive does atomic_read first and
x86 can reorder loads before stores. lfence isn't enough: store can
pass lfence, turning it into a nop. A compiler barrier would be more
than enough as CPU needs to stall for unbelievably long to use fences.
This patch doesn't do anything in kvm_pit_reset_reinject, because any
order of resets can race, but the result differs by at most one
interrupt, which is ok, because it's the same result as if the reset
happened at a slightly different time. (Original code didn't protect
the reset path with a proper lock, so users have to be robust.)
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-03-03 04:56:41 +07:00
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atomic_t irq_ack;
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2008-07-27 03:01:01 +07:00
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struct kvm_irq_ack_notifier irq_ack_notifier;
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2008-01-28 04:10:22 +07:00
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};
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struct kvm_pit {
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struct kvm_io_device dev;
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struct kvm_io_device speaker_dev;
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struct kvm *kvm;
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struct kvm_kpit_state pit_state;
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2008-10-15 19:15:06 +07:00
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int irq_source_id;
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2009-01-04 23:06:06 +07:00
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struct kvm_irq_mask_notifier mask_notifier;
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2012-04-24 21:40:17 +07:00
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struct kthread_worker worker;
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struct task_struct *worker_task;
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struct kthread_work expired;
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2008-01-28 04:10:22 +07:00
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};
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#define KVM_PIT_BASE_ADDRESS 0x40
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#define KVM_SPEAKER_BASE_ADDRESS 0x61
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#define KVM_PIT_MEM_LENGTH 4
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#define KVM_PIT_FREQ 1193181
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#define KVM_MAX_PIT_INTR_INTERVAL HZ / 100
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#define KVM_PIT_CHANNEL_MASK 0x3
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2009-05-15 03:42:53 +07:00
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struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags);
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2008-01-28 04:10:22 +07:00
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void kvm_free_pit(struct kvm *kvm);
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2016-03-03 04:56:43 +07:00
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void kvm_pit_load_count(struct kvm_pit *pit, int channel, u32 val,
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int hpet_legacy_start);
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2016-03-03 04:56:45 +07:00
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void kvm_pit_set_reinject(struct kvm_pit *pit, bool reinject);
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2008-01-28 04:10:22 +07:00
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#endif
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