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: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a3e9409..2c75b40 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -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);
 

diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 81cf4fa..1df8fb9 100644 (file)
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -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'
  */

diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 26fd54d..ef61d52 100644 (file)
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -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)
 {

diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
index 32872a0..a30abfe 100644 (file)
--- a/virt/kvm/ioapic.h
+++ b/virt/kvm/ioapic.h
@@ -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);

diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
index a6a0365..cc59c68 100644 (file)
--- a/virt/kvm/irq_comm.c
+++ b/virt/kvm/irq_comm.c
@@ -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 @@ unlock:
 
 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);
 }