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Commit 7543a635 authored by Steve Rutherford's avatar Steve Rutherford Committed by Paolo Bonzini
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KVM: x86: Add KVM exit for IOAPIC EOIs 



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: default avatarSteve Rutherford <srutherford@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 49df6397

Documentation/virtual/kvm/api.txt

+12 −0
Original line number Diff line number Diff line
@@ -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];

	};

arch/x86/include/asm/kvm_host.h

+2 −0
Original line number Diff line number Diff line
@@ -574,6 +574,8 @@ struct kvm_vcpu_arch { 
	struct {

		bool pv_unhalted;

	} pv;



	int pending_ioapic_eoi;

};



struct kvm_lpage_info {

arch/x86/kvm/lapic.c

+17 −7
Original line number Diff line number Diff line
@@ -877,8 +877,19 @@ 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;



	/* 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
@@ -886,7 +897,6 @@ static void kvm_ioapic_send_eoi(struct kvm_lapic *apic, int vector) 


	kvm_ioapic_update_eoi(apic->vcpu, vector, trigger_mode);

}

}



static int apic_set_eoi(struct kvm_lapic *apic)

{

arch/x86/kvm/x86.c

+11 −0
Original line number Diff line number Diff line
@@ -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))

include/linux/kvm_host.h

+1 −1
Original line number Diff line number Diff line
@@ -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