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KVM: x86: Add KVM exit for IOAPIC EOIs

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Adds KVM_EXIT_IOAPIC_EOI which allows the kernel to EOI
level-triggered IOAPIC interrupts.

Uses a per VCPU exit bitmap to decide whether or not the IOAPIC needs
to be informed (which is identical to the EOI_EXIT_BITMAP field used
by modern x86 processors, but can also be used to elide kvm IOAPIC EOI
exits on older processors).

[Note: A prototype using ResampleFDs found that decoupling the EOI
from the VCPU's thread made it possible for the VCPU to not see a
recent EOI after reentering the guest. This does not match real
hardware.]

Compile tested for Intel x86.

Signed-off-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Steve Rutherford 2015-07-29 23:21:41 -07:00 committed by Paolo Bonzini
parent 49df6397ed
commit 7543a635aa
6 changed files with 48 additions and 8 deletions
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12
Documentation/virtual/kvm/api.txt
View File

@ -3309,6 +3309,18 @@ Valid values for 'type' are:
to ignore the request, or to gather VM memory core dump and/or
reset/shutdown of the VM.
/* KVM_EXIT_IOAPIC_EOI */
struct {
__u8 vector;
} eoi;
Indicates that the VCPU's in-kernel local APIC received an EOI for a
level-triggered IOAPIC interrupt. This exit only triggers when the
IOAPIC is implemented in userspace (i.e. KVM_CAP_SPLIT_IRQCHIP is enabled);
the userspace IOAPIC should process the EOI and retrigger the interrupt if
it is still asserted. Vector is the LAPIC interrupt vector for which the
EOI was received.
/* Fix the size of the union. */
char padding[256];
};

2
arch/x86/include/asm/kvm_host.h
View File

@ -574,6 +574,8 @@ struct kvm_vcpu_arch {
struct {
bool pv_unhalted;
} pv;
int pending_ioapic_eoi;
};
struct kvm_lpage_info {

24
arch/x86/kvm/lapic.c
View File

@ -877,15 +877,25 @@ static bool kvm_ioapic_handles_vector(struct kvm_lapic *apic, int vector)
static void kvm_ioapic_send_eoi(struct kvm_lapic *apic, int vector)
{
if (kvm_ioapic_handles_vector(apic, vector)) {
int trigger_mode;
if (apic_test_vector(vector, apic->regs + APIC_TMR))
trigger_mode = IOAPIC_LEVEL_TRIG;
else
trigger_mode = IOAPIC_EDGE_TRIG;
int trigger_mode;
kvm_ioapic_update_eoi(apic->vcpu, vector, trigger_mode);
/* Eoi the ioapic only if the ioapic doesn't own the vector. */
if (!kvm_ioapic_handles_vector(apic, vector))
return;
/* Request a KVM exit to inform the userspace IOAPIC. */
if (irqchip_split(apic->vcpu->kvm)) {
apic->vcpu->arch.pending_ioapic_eoi = vector;
kvm_make_request(KVM_REQ_IOAPIC_EOI_EXIT, apic->vcpu);
return;
}
if (apic_test_vector(vector, apic->regs + APIC_TMR))
trigger_mode = IOAPIC_LEVEL_TRIG;
else
trigger_mode = IOAPIC_EDGE_TRIG;
kvm_ioapic_update_eoi(apic->vcpu, vector, trigger_mode);
}
static int apic_set_eoi(struct kvm_lapic *apic)

11
arch/x86/kvm/x86.c
View File

@ -6271,6 +6271,17 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
kvm_pmu_handle_event(vcpu);
if (kvm_check_request(KVM_REQ_PMI, vcpu))
kvm_pmu_deliver_pmi(vcpu);
if (kvm_check_request(KVM_REQ_IOAPIC_EOI_EXIT, vcpu)) {
BUG_ON(vcpu->arch.pending_ioapic_eoi > 255);
if (test_bit(vcpu->arch.pending_ioapic_eoi,
(void *) vcpu->arch.eoi_exit_bitmap)) {
vcpu->run->exit_reason = KVM_EXIT_IOAPIC_EOI;
vcpu->run->eoi.vector =
vcpu->arch.pending_ioapic_eoi;
r = 0;
goto out;
}
}
if (kvm_check_request(KVM_REQ_SCAN_IOAPIC, vcpu))
vcpu_scan_ioapic(vcpu);
if (kvm_check_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu))

2
include/linux/kvm_host.h
View File

@ -140,6 +140,7 @@ static inline bool is_error_page(struct page *page)
#define KVM_REQ_APIC_PAGE_RELOAD 25
#define KVM_REQ_SMI 26
#define KVM_REQ_HV_CRASH 27
#define KVM_REQ_IOAPIC_EOI_EXIT 28
#define KVM_USERSPACE_IRQ_SOURCE_ID 0
#define KVM_IRQFD_RESAMPLE_IRQ_SOURCE_ID 1
@ -1146,4 +1147,3 @@ static inline void kvm_vcpu_set_dy_eligible(struct kvm_vcpu *vcpu, bool val)
}
#endif /* CONFIG_HAVE_KVM_CPU_RELAX_INTERCEPT */
#endif

5
include/uapi/linux/kvm.h
View File

@ -183,6 +183,7 @@ struct kvm_s390_skeys {
#define KVM_EXIT_EPR 23
#define KVM_EXIT_SYSTEM_EVENT 24
#define KVM_EXIT_S390_STSI 25
#define KVM_EXIT_IOAPIC_EOI 26
/* For KVM_EXIT_INTERNAL_ERROR */
/* Emulate instruction failed. */
@ -333,6 +334,10 @@ struct kvm_run {
__u8 sel1;
__u16 sel2;
} s390_stsi;
/* KVM_EXIT_IOAPIC_EOI */
struct {
__u8 vector;
} eoi;
/* Fix the size of the union. */
char padding[256];
};