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Date: Thu, 19 Jul 2012 00:52:28 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
Alex Williamson <alex.williamson@...hat.com>, gleb@...hat.com,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] 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:
CPU 0 clears bit in irq_states. CPU 0 reads irq_state as 0.
CPU 1 sets bit in irq_states. 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.
Note that above is valid behaviour if CPU0 and CPU1 are using different
source ids.
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@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
This survives stress testing for me (though I only tried virtio, not
device assignment).
Avi, Marcelo, though we have not observed this in the field,
it's a bugfix so probably 3.5 material?
I assume yes so the patch is against 3.5-rc7.
Also stable? It's a very old bug.
arch/x86/include/asm/kvm_host.h | 15 ++++++++++++++-
arch/x86/kvm/i8259.c | 14 ++++++++++++--
virt/kvm/ioapic.c | 13 ++++++++++++-
virt/kvm/ioapic.h | 4 +++-
virt/kvm/irq_comm.c | 31 ++++---------------------------
5 files changed, 45 insertions(+), 32 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index db7c1f2..fe6e9f1 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -802,7 +802,20 @@ 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..95b504b 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -188,13 +188,14 @@ 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 src_id, int l)
{
- struct kvm_pic *s = opaque;
int ret = -1;
+ int level;
pic_lock(s);
if (irq >= 0 && irq < PIC_NUM_PINS) {
+ level = kvm_irq_line_state(&s->irq_states[irq], src_id, l);
ret = pic_set_irq1(&s->pics[irq >> 3], irq & 7, level);
pic_update_irq(s);
trace_kvm_pic_set_irq(irq >> 3, irq & 7, s->pics[irq >> 3].elcr,
@@ -205,6 +206,15 @@ int kvm_pic_set_irq(void *opaque, int irq, int level)
return ret;
}
+void kvm_pic_clear_all(struct kvm_pic *s, int src_id)
+{
+ int i;
+ pic_lock(s);
+ for (i = 0; i < PIC_NUM_PINS; i++)
+ __clear_bit(src_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..268b332 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -191,17 +191,19 @@ 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 src_id, int l)
{
u32 old_irr;
u32 mask = 1 << irq;
union kvm_ioapic_redirect_entry entry;
int ret = 1;
+ int level;
spin_lock(&ioapic->lock);
old_irr = ioapic->irr;
if (irq >= 0 && irq < IOAPIC_NUM_PINS) {
entry = ioapic->redirtbl[irq];
+ level = kvm_irq_line_state(&ioapic->irq_states[irq], src_id, l);
level ^= entry.fields.polarity;
if (!level)
ioapic->irr &= ~mask;
@@ -221,6 +223,15 @@ 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 src_id)
+{
+ int i;
+ spin_lock(&ioapic->lock);
+ for (i = 0; i < KVM_IOAPIC_NUM_PINS; i++)
+ __clear_bit(src_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
--- 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 5afb431..83402d7 100644
--- 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);
}
--
MST
--
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