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Commit 1a577b72 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Marcelo Tosatti
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KVM: fix race with level interrupts 



When more than 1 source id is in use for the same GSI, we have the
following race related to handling irq_states race:

CPU 0 clears bit 0. CPU 0 read irq_state as 0. CPU 1 sets level to 1.
CPU 1 calls kvm_ioapic_set_irq(1). CPU 0 calls kvm_ioapic_set_irq(0).
Now ioapic thinks the level is 0 but irq_state is not 0.

Fix by performing all irq_states bitmap handling under pic/ioapic lock.
This also removes the need for atomics with irq_states handling.

Reported-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent d63d3e62

arch/x86/include/asm/kvm_host.h

+14 −1
Original line number Diff line number Diff line
@@ -816,7 +816,20 @@ int kvm_read_guest_page_mmu(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, 
void kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault);

bool kvm_require_cpl(struct kvm_vcpu *vcpu, int required_cpl);



int kvm_pic_set_irq(void *opaque, int irq, int level);

static inline int __kvm_irq_line_state(unsigned long *irq_state,

				       int irq_source_id, int level)

{

	/* Logical OR for level trig interrupt */

	if (level)

		__set_bit(irq_source_id, irq_state);

	else

		__clear_bit(irq_source_id, irq_state);



	return !!(*irq_state);

}



int kvm_pic_set_irq(struct kvm_pic *pic, int irq, int irq_source_id, int level);

void kvm_pic_clear_all(struct kvm_pic *pic, int irq_source_id);



void kvm_inject_nmi(struct kvm_vcpu *vcpu);

arch/x86/kvm/i8259.c

+14 −3
Original line number Diff line number Diff line
@@ -188,14 +188,15 @@ void kvm_pic_update_irq(struct kvm_pic *s) 
	pic_unlock(s);

}



int kvm_pic_set_irq(void *opaque, int irq, int level)

int kvm_pic_set_irq(struct kvm_pic *s, int irq, int irq_source_id, int level)

{

	struct kvm_pic *s = opaque;

	int ret = -1;



	pic_lock(s);

	if (irq >= 0 && irq < PIC_NUM_PINS) {

		ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, level);

		int irq_level = __kvm_irq_line_state(&s->irq_states[irq],

						     irq_source_id, level);

		ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, irq_level);

		pic_update_irq(s);

		trace_kvm_pic_set_irq(irq >> 3, irq & 7, s->pics[irq >> 3].elcr,

				      s->pics[irq >> 3].imr, ret == 0);
@@ -205,6 +206,16 @@ int kvm_pic_set_irq(void *opaque, int irq, int level) 
	return ret;

}



void kvm_pic_clear_all(struct kvm_pic *s, int irq_source_id)

{

	int i;



	pic_lock(s);

	for (i = 0; i < PIC_NUM_PINS; i++)

		__clear_bit(irq_source_id, &s->irq_states[i]);

	pic_unlock(s);

}



/*

 * acknowledge interrupt 'irq'

 */

virt/kvm/ioapic.c

+16 −3
Original line number Diff line number Diff line
@@ -191,7 +191,8 @@ static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq) 
	return kvm_irq_delivery_to_apic(ioapic->kvm, NULL, &irqe);

}



int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)

int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,

		       int level)

{

	u32 old_irr;

	u32 mask = 1 << irq;
@@ -201,9 +202,11 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level) 
	spin_lock(&ioapic->lock);

	old_irr = ioapic->irr;

	if (irq >= 0 && irq < IOAPIC_NUM_PINS) {

		int irq_level = __kvm_irq_line_state(&ioapic->irq_states[irq],

						     irq_source_id, level);

		entry = ioapic->redirtbl[irq];

		level ^= entry.fields.polarity;

		if (!level)

		irq_level ^= entry.fields.polarity;

		if (!irq_level)

			ioapic->irr &= ~mask;

		else {

			int edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);
@@ -221,6 +224,16 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level) 
	return ret;

}



void kvm_ioapic_clear_all(struct kvm_ioapic *ioapic, int irq_source_id)

{

	int i;



	spin_lock(&ioapic->lock);

	for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++)

		__clear_bit(irq_source_id, &ioapic->irq_states[i]);

	spin_unlock(&ioapic->lock);

}



static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,

				     int trigger_mode)

{

virt/kvm/ioapic.h

+3 −1
Original line number Diff line number Diff line
@@ -74,7 +74,9 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode); 
bool kvm_ioapic_handles_vector(struct kvm *kvm, int vector);

int kvm_ioapic_init(struct kvm *kvm);

void kvm_ioapic_destroy(struct kvm *kvm);

int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);

int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,

		       int level);

void kvm_ioapic_clear_all(struct kvm_ioapic *ioapic, int irq_source_id);

void kvm_ioapic_reset(struct kvm_ioapic *ioapic);

int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,

		struct kvm_lapic_irq *irq);

virt/kvm/irq_comm.c

+4 −27
Original line number Diff line number Diff line
@@ -33,26 +33,12 @@ 


#include "ioapic.h"



static inline int kvm_irq_line_state(unsigned long *irq_state,

				     int irq_source_id, int level)

{

	/* Logical OR for level trig interrupt */

	if (level)

		set_bit(irq_source_id, irq_state);

	else

		clear_bit(irq_source_id, irq_state);



	return !!(*irq_state);

}



static int kvm_set_pic_irq(struct kvm_kernel_irq_routing_entry *e,

			   struct kvm *kvm, int irq_source_id, int level)

{

#ifdef CONFIG_X86

	struct kvm_pic *pic = pic_irqchip(kvm);

	level = kvm_irq_line_state(&pic->irq_states[e->irqchip.pin],

				   irq_source_id, level);

	return kvm_pic_set_irq(pic, e->irqchip.pin, level);

	return kvm_pic_set_irq(pic, e->irqchip.pin, irq_source_id, level);

#else

	return -1;

#endif
@@ -62,10 +48,7 @@ static int kvm_set_ioapic_irq(struct kvm_kernel_irq_routing_entry *e, 
			      struct kvm *kvm, int irq_source_id, int level)

{

	struct kvm_ioapic *ioapic = kvm->arch.vioapic;

	level = kvm_irq_line_state(&ioapic->irq_states[e->irqchip.pin],

				   irq_source_id, level);



	return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, level);

	return kvm_ioapic_set_irq(ioapic, e->irqchip.pin, irq_source_id, level);

}



inline static bool kvm_is_dm_lowest_prio(struct kvm_lapic_irq *irq)
@@ -249,8 +232,6 @@ int kvm_request_irq_source_id(struct kvm *kvm) 


void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id)

{

	int i;



	ASSERT(irq_source_id != KVM_USERSPACE_IRQ_SOURCE_ID);



	mutex_lock(&kvm->irq_lock);
@@ -263,14 +244,10 @@ void kvm_free_irq_source_id(struct kvm *kvm, int irq_source_id) 
	if (!irqchip_in_kernel(kvm))

		goto unlock;



	for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++) {

		clear_bit(irq_source_id, &kvm->arch.vioapic->irq_states[i]);

		if (i >= 16)

			continue;

	kvm_ioapic_clear_all(kvm->arch.vioapic, irq_source_id);

#ifdef CONFIG_X86

		clear_bit(irq_source_id, &pic_irqchip(kvm)->irq_states[i]);

	kvm_pic_clear_all(pic_irqchip(kvm), irq_source_id);

#endif

	}

unlock:

	mutex_unlock(&kvm->irq_lock);

}