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KVM: PIT support for HPET legacy mode

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When kvm is in hpet_legacy_mode, the hpet is providing the timer
interrupt and the pit should not be. So in legacy mode, the pit timer
is destroyed, but the *state* of the pit is maintained. So if kvm or
the guest tries to modify the state of the pit, this modification is
accepted, *except* that the timer isn't actually started. When we exit
hpet_legacy_mode, the current state of the pit (which is up to date
since we've been accepting modifications) is used to restart the pit
timer.

The saved_mode code in kvm_pit_load_count temporarily changes mode to
0xff in order to destroy the timer, but then restores the actual
value, again maintaining "current" state of the pit for possible later
reenablement.

[avi: add some reserved storage in the ioctl; make SET_PIT2 IOW]
[marcelo: fix memory corruption due to reserved storage]

Signed-off-by: Beth Kon <eak@us.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Beth Kon 2009-07-07 11:50:38 -04:00 • committed by Avi Kivity
parent 0d1de2d901
commit e9f4275732
5 changed files with 93 additions and 6 deletions
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6
include/linux/kvm.h
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@ -409,6 +409,9 @@ struct kvm_guest_debug {
#define KVM_CAP_PIT2 33
#endif
#define KVM_CAP_SET_BOOT_CPU_ID 34
#ifdef __KVM_HAVE_PIT_STATE2
#define KVM_CAP_PIT_STATE2 35
#endif
#ifdef KVM_CAP_IRQ_ROUTING
@ -586,6 +589,9 @@ struct kvm_debug_guest {
#define KVM_IA64_VCPU_GET_STACK _IOR(KVMIO, 0x9a, void *)
#define KVM_IA64_VCPU_SET_STACK _IOW(KVMIO, 0x9b, void *)
#define KVM_GET_PIT2 _IOR(KVMIO, 0x9f, struct kvm_pit_state2)
#define KVM_SET_PIT2 _IOW(KVMIO, 0xa0, struct kvm_pit_state2)
#define KVM_TRC_INJ_VIRQ (KVM_TRC_HANDLER + 0x02)
#define KVM_TRC_REDELIVER_EVT (KVM_TRC_HANDLER + 0x03)
#define KVM_TRC_PEND_INTR (KVM_TRC_HANDLER + 0x04)