KVM: protect assigned dev workqueue, int handler and irq acker
kvm_assigned_dev_ack_irq is vulnerable to a race condition with the
interrupt handler function. It does:
if (dev->host_irq_disabled) {
enable_irq(dev->host_irq);
dev->host_irq_disabled = false;
}
If an interrupt triggers before the host->dev_irq_disabled assignment,
it will disable the interrupt and set dev->host_irq_disabled to true.
On return to kvm_assigned_dev_ack_irq, dev->host_irq_disabled is set to
false, and the next kvm_assigned_dev_ack_irq call will fail to reenable
it.
Other than that, having the interrupt handler and work handlers run in
parallel sounds like asking for trouble (could not spot any obvious
problem, but better not have to, its fragile).
CC: sheng.yang@intel.com
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1618162..aacc544 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -345,6 +345,7 @@
int flags;
struct pci_dev *dev;
struct kvm *kvm;
+ spinlock_t assigned_dev_lock;
};
struct kvm_irq_mask_notifier {
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 29c0afb..687d113 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -42,6 +42,7 @@
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/bitops.h>
+#include <linux/spinlock.h>
#include <asm/processor.h>
#include <asm/io.h>
@@ -130,6 +131,7 @@
* finer-grained lock, update this
*/
mutex_lock(&kvm->lock);
+ spin_lock_irq(&assigned_dev->assigned_dev_lock);
if (assigned_dev->irq_requested_type & KVM_DEV_IRQ_HOST_MSIX) {
struct kvm_guest_msix_entry *guest_entries =
assigned_dev->guest_msix_entries;
@@ -156,18 +158,21 @@
}
}
+ spin_unlock_irq(&assigned_dev->assigned_dev_lock);
mutex_unlock(&assigned_dev->kvm->lock);
}
static irqreturn_t kvm_assigned_dev_intr(int irq, void *dev_id)
{
+ unsigned long flags;
struct kvm_assigned_dev_kernel *assigned_dev =
(struct kvm_assigned_dev_kernel *) dev_id;
+ spin_lock_irqsave(&assigned_dev->assigned_dev_lock, flags);
if (assigned_dev->irq_requested_type & KVM_DEV_IRQ_HOST_MSIX) {
int index = find_index_from_host_irq(assigned_dev, irq);
if (index < 0)
- return IRQ_HANDLED;
+ goto out;
assigned_dev->guest_msix_entries[index].flags |=
KVM_ASSIGNED_MSIX_PENDING;
}
@@ -177,6 +182,8 @@
disable_irq_nosync(irq);
assigned_dev->host_irq_disabled = true;
+out:
+ spin_unlock_irqrestore(&assigned_dev->assigned_dev_lock, flags);
return IRQ_HANDLED;
}
@@ -184,6 +191,7 @@
static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian)
{
struct kvm_assigned_dev_kernel *dev;
+ unsigned long flags;
if (kian->gsi == -1)
return;
@@ -196,10 +204,12 @@
/* The guest irq may be shared so this ack may be
* from another device.
*/
+ spin_lock_irqsave(&dev->assigned_dev_lock, flags);
if (dev->host_irq_disabled) {
enable_irq(dev->host_irq);
dev->host_irq_disabled = false;
}
+ spin_unlock_irqrestore(&dev->assigned_dev_lock, flags);
}
static void deassign_guest_irq(struct kvm *kvm,
@@ -615,6 +625,7 @@
match->host_devfn = assigned_dev->devfn;
match->flags = assigned_dev->flags;
match->dev = dev;
+ spin_lock_init(&match->assigned_dev_lock);
match->irq_source_id = -1;
match->kvm = kvm;
match->ack_notifier.irq_acked = kvm_assigned_dev_ack_irq;
