PCI 2.3 allows to generically disable IRQ sources at device level. This
enables us to share legacy IRQs of such devices with other host devices
when passing them to a guest.
The new IRQ sharing feature introduced here is optional, user space has
to request it explicitly. Moreover, user space can inform us about its
view of PCI_COMMAND_INTX_DISABLE so that we can avoid unmasking the
interrupt and signaling it if the guest masked it via the virtualized
PCI config space.
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
Changes in v2:
- clarified API doc according to review comments
- moved KVM_CAP_PCI_2_3 out of the range that PPC silently occupied
This still depends on
PCI: Rework config space blocking services
PCI: Introduce INTx check & mask API
from current linux-next/master.
Documentation/virtual/kvm/api.txt | 31 ++++++
arch/x86/kvm/x86.c | 1 +
include/linux/kvm.h | 6 +
include/linux/kvm_host.h | 2 +
virt/kvm/assigned-dev.c | 208 +++++++++++++++++++++++++++++++-----
5 files changed, 219 insertions(+), 29 deletions(-)
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 7ca6962..d606655 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1169,6 +1169,14 @@ following flags are specified:
/* Depends on KVM_CAP_IOMMU */
#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
+/* The following two depend on KVM_CAP_PCI_2_3 */
+#define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
+#define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
+
+If KVM_DEV_ASSIGN_PCI_2_3 is set, the kernel will manage legacy INTx interrupts
+via the PCI-2.3-compliant device-level mask, thus enable IRQ sharing with other
+assigned devices or host devices. KVM_DEV_ASSIGN_MASK_INTX specifies the
+guest's view on the INTx mask, see KVM_ASSIGN_SET_INTX_MASK for details.
The KVM_DEV_ASSIGN_ENABLE_IOMMU flag is a mandatory option to ensure
isolation of the device. Usages not specifying this flag are deprecated.
@@ -1409,6 +1417,29 @@ The following flags are defined:
If datamatch flag is set, the event will be signaled only if the written value
to the registered address is equal to datamatch in struct kvm_ioeventfd.
+4.59 KVM_ASSIGN_SET_INTX_MASK
+
+Capability: KVM_CAP_PCI_2_3
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_assigned_pci_dev (in)
+Returns: 0 on success, -1 on error
+
+Informs the kernel about the guest's view on the INTx mask. As long as the
+guest masks the legacy INTx, the kernel will refrain from unmasking it at
+hardware level and will not assert the guest's IRQ line. User space is still
+responsible for applying this state to the assigned device's real config space
+by setting or clearing the Interrupt Disable bit 10 in the Command register.
+
+To avoid that the kernel overwrites the state user space wants to set,
+KVM_ASSIGN_SET_INTX_MASK has to be called prior to updating the config space.
+Moreover, user space has to write back its own view on the Interrupt Disable
+bit whenever modifying the Command word.
+
+See KVM_ASSIGN_DEV_IRQ for the data structure. The target device is specified
+by assigned_dev_id. In the flags field, only KVM_DEV_ASSIGN_MASK_INTX is
+evaluated.
+
4.62 KVM_CREATE_SPAPR_TCE
Capability: KVM_CAP_SPAPR_TCE
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f0fa3fb..3c6cff4 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2077,6 +2077,7 @@ int kvm_dev_ioctl_check_extension(long ext)
case KVM_CAP_XSAVE:
case KVM_CAP_ASYNC_PF:
case KVM_CAP_GET_TSC_KHZ:
+ case KVM_CAP_PCI_2_3:
r = 1;
break;
case KVM_CAP_COALESCED_MMIO:
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 245bcb3..a075198f7 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -585,6 +585,7 @@ struct kvm_ppc_pvinfo {
#define KVM_CAP_TSC_DEADLINE_TIMER 72
#define KVM_CAP_S390_UCONTROL 73
#define KVM_CAP_SYNC_REGS 74
+#define KVM_CAP_PCI_2_3 75
#ifdef KVM_CAP_IRQ_ROUTING
@@ -735,6 +736,9 @@ struct kvm_s390_ucas_mapping {
/* Available with KVM_CAP_TSC_CONTROL */
#define KVM_SET_TSC_KHZ _IO(KVMIO, 0xa2)
#define KVM_GET_TSC_KHZ _IO(KVMIO, 0xa3)
+/* Available with KVM_CAP_PCI_2_3 */
+#define KVM_ASSIGN_SET_INTX_MASK _IOW(KVMIO, 0xa4, \
+ struct kvm_assigned_pci_dev)
/*
* ioctls for vcpu fds
@@ -803,6 +807,8 @@ struct kvm_s390_ucas_mapping {
#define KVM_ALLOCATE_RMA _IOR(KVMIO, 0xa9, struct kvm_allocate_rma)
#define KVM_DEV_ASSIGN_ENABLE_IOMMU (1 << 0)
+#define KVM_DEV_ASSIGN_PCI_2_3 (1 << 1)
+#define KVM_DEV_ASSIGN_MASK_INTX (1 << 2)
struct kvm_assigned_pci_dev {
__u32 assigned_dev_id;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d4d4d70..17c48ac 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -547,6 +547,7 @@ struct kvm_assigned_dev_kernel {
unsigned int entries_nr;
int host_irq;
bool host_irq_disabled;
+ bool pci_2_3;
struct msix_entry *host_msix_entries;
int guest_irq;
struct msix_entry *guest_msix_entries;
@@ -556,6 +557,7 @@ struct kvm_assigned_dev_kernel {
struct pci_dev *dev;
struct kvm *kvm;
spinlock_t intx_lock;
+ struct mutex intx_mask_lock;
char irq_name[32];
struct pci_saved_state *pci_saved_state;
};
diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index 758e3b3..b35aba9 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -57,22 +57,66 @@ static int find_index_from_host_irq(struct kvm_assigned_dev_kernel
return index;
}
-static irqreturn_t kvm_assigned_dev_thread(int irq, void *dev_id)
+static irqreturn_t kvm_assigned_dev_intx(int irq, void *dev_id)
{
struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
+ int ret;
- if (assigned_dev->irq_requested_type & KVM_DEV_IRQ_HOST_INTX) {
- spin_lock(&assigned_dev->intx_lock);
+ spin_lock(&assigned_dev->intx_lock);
+ if (pci_check_and_mask_intx(assigned_dev->dev)) {
+ assigned_dev->host_irq_disabled = true;
+ ret = IRQ_WAKE_THREAD;
+ } else
+ ret = IRQ_NONE;
+ spin_unlock(&assigned_dev->intx_lock);
+
+ return ret;
+}
+
+static void
+kvm_assigned_dev_raise_guest_irq(struct kvm_assigned_dev_kernel *assigned_dev,
+ int vector)
+{
+ if (unlikely(assigned_dev->irq_requested_type &
+ KVM_DEV_IRQ_GUEST_INTX)) {
+ mutex_lock(&assigned_dev->intx_mask_lock);
+ if (!(assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX))
+ kvm_set_irq(assigned_dev->kvm,
+ assigned_dev->irq_source_id, vector, 1);
+ mutex_unlock(&assigned_dev->intx_mask_lock);
+ } else
+ kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
+ vector, 1);
+}
+
+static irqreturn_t kvm_assigned_dev_thread_intx(int irq, void *dev_id)
+{
+ struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
+
+ if (!(assigned_dev->flags & KVM_DEV_ASSIGN_PCI_2_3)) {
+ spin_lock_irq(&assigned_dev->intx_lock);
disable_irq_nosync(irq);
assigned_dev->host_irq_disabled = true;
- spin_unlock(&assigned_dev->intx_lock);
+ spin_unlock_irq(&assigned_dev->intx_lock);
}
- kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
- assigned_dev->guest_irq, 1);
+ kvm_assigned_dev_raise_guest_irq(assigned_dev,
+ assigned_dev->guest_irq);
+
+ return IRQ_HANDLED;
+}
+
+#ifdef __KVM_HAVE_MSI
+static irqreturn_t kvm_assigned_dev_thread_msi(int irq, void *dev_id)
+{
+ struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
+
+ kvm_assigned_dev_raise_guest_irq(assigned_dev,
+ assigned_dev->guest_irq);
return IRQ_HANDLED;
}
+#endif
#ifdef __KVM_HAVE_MSIX
static irqreturn_t kvm_assigned_dev_thread_msix(int irq, void *dev_id)
@@ -83,8 +127,7 @@ static irqreturn_t kvm_assigned_dev_thread_msix(int irq, void *dev_id)
if (index >= 0) {
vector = assigned_dev->guest_msix_entries[index].vector;
- kvm_set_irq(assigned_dev->kvm, assigned_dev->irq_source_id,
- vector, 1);
+ kvm_assigned_dev_raise_guest_irq(assigned_dev, vector);
}
return IRQ_HANDLED;
@@ -100,15 +143,31 @@ static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian)
kvm_set_irq(dev->kvm, dev->irq_source_id, dev->guest_irq, 0);
- /* The guest irq may be shared so this ack may be
- * from another device.
- */
- spin_lock(&dev->intx_lock);
- if (dev->host_irq_disabled) {
- enable_irq(dev->host_irq);
- dev->host_irq_disabled = false;
+ mutex_lock(&dev->intx_mask_lock);
+
+ if (!(dev->flags & KVM_DEV_ASSIGN_MASK_INTX)) {
+ bool reassert = false;
+
+ spin_lock_irq(&dev->intx_lock);
+ /*
+ * The guest IRQ may be shared so this ack can come from an
+ * IRQ for another guest device.
+ */
+ if (dev->host_irq_disabled) {
+ if (!(dev->flags & KVM_DEV_ASSIGN_PCI_2_3))
+ enable_irq(dev->host_irq);
+ else if (!pci_check_and_unmask_intx(dev->dev))
+ reassert = true;
+ dev->host_irq_disabled = reassert;
+ }
+ spin_unlock_irq(&dev->intx_lock);
+
+ if (reassert)
+ kvm_set_irq(dev->kvm, dev->irq_source_id,
+ dev->guest_irq, 1);
}
- spin_unlock(&dev->intx_lock);
+
+ mutex_unlock(&dev->intx_mask_lock);
}
static void deassign_guest_irq(struct kvm *kvm,
@@ -156,7 +215,13 @@ static void deassign_host_irq(struct kvm *kvm,
pci_disable_msix(assigned_dev->dev);
} else {
/* Deal with MSI and INTx */
- disable_irq(assigned_dev->host_irq);
+ if (assigned_dev->flags & KVM_DEV_ASSIGN_PCI_2_3) {
+ spin_lock_irq(&assigned_dev->intx_lock);
+ pci_intx(assigned_dev->dev, false);
+ spin_unlock_irq(&assigned_dev->intx_lock);
+ synchronize_irq(assigned_dev->host_irq);
+ } else
+ disable_irq(assigned_dev->host_irq);
free_irq(assigned_dev->host_irq, assigned_dev);
@@ -237,15 +302,34 @@ void kvm_free_all_assigned_devices(struct kvm *kvm)
static int assigned_device_enable_host_intx(struct kvm *kvm,
struct kvm_assigned_dev_kernel *dev)
{
+ irq_handler_t irq_handler;
+ unsigned long flags;
+
dev->host_irq = dev->dev->irq;
- /* Even though this is PCI, we don't want to use shared
- * interrupts. Sharing host devices with guest-assigned devices
- * on the same interrupt line is not a happy situation: there
- * are going to be long delays in accepting, acking, etc.
+
+ /*
+ * We can only share the IRQ line with other host devices if we are
+ * able to disable the IRQ source at device-level - independently of
+ * the guest driver. Otherwise host devices may suffer from unbounded
+ * IRQ latencies when the guest keeps the line asserted.
*/
- if (request_threaded_irq(dev->host_irq, NULL, kvm_assigned_dev_thread,
- IRQF_ONESHOT, dev->irq_name, dev))
+ if (dev->flags & KVM_DEV_ASSIGN_PCI_2_3) {
+ irq_handler = kvm_assigned_dev_intx;
+ flags = IRQF_SHARED;
+ } else {
+ irq_handler = NULL;
+ flags = IRQF_ONESHOT;
+ }
+ if (request_threaded_irq(dev->host_irq, irq_handler,
+ kvm_assigned_dev_thread_intx, flags,
+ dev->irq_name, dev))
return -EIO;
+
+ if (dev->flags & KVM_DEV_ASSIGN_PCI_2_3) {
+ spin_lock_irq(&dev->intx_lock);
+ pci_intx(dev->dev, true);
+ spin_unlock_irq(&dev->intx_lock);
+ }
return 0;
}
@@ -262,8 +346,9 @@ static int assigned_device_enable_host_msi(struct kvm *kvm,
}
dev->host_irq = dev->dev->irq;
- if (request_threaded_irq(dev->host_irq, NULL, kvm_assigned_dev_thread,
- 0, dev->irq_name, dev)) {
+ if (request_threaded_irq(dev->host_irq, NULL,
+ kvm_assigned_dev_thread_msi, 0,
+ dev->irq_name, dev)) {
pci_disable_msi(dev->dev);
return -EIO;
}
@@ -321,7 +406,6 @@ static int assigned_device_enable_guest_msi(struct kvm *kvm,
{
dev->guest_irq = irq->guest_irq;
dev->ack_notifier.gsi = -1;
- dev->host_irq_disabled = false;
return 0;
}
#endif
@@ -333,7 +417,6 @@ static int assigned_device_enable_guest_msix(struct kvm *kvm,
{
dev->guest_irq = irq->guest_irq;
dev->ack_notifier.gsi = -1;
- dev->host_irq_disabled = false;
return 0;
}
#endif
@@ -367,6 +450,7 @@ static int assign_host_irq(struct kvm *kvm,
default:
r = -EINVAL;
}
+ dev->host_irq_disabled = false;
if (!r)
dev->irq_requested_type |= host_irq_type;
@@ -468,6 +552,7 @@ static int kvm_vm_ioctl_deassign_dev_irq(struct kvm *kvm,
{
int r = -ENODEV;
struct kvm_assigned_dev_kernel *match;
+ unsigned long irq_type;
mutex_lock(&kvm->lock);
@@ -476,7 +561,9 @@ static int kvm_vm_ioctl_deassign_dev_irq(struct kvm *kvm,
if (!match)
goto out;
- r = kvm_deassign_irq(kvm, match, assigned_irq->flags);
+ irq_type = assigned_irq->flags & (KVM_DEV_IRQ_HOST_MASK |
+ KVM_DEV_IRQ_GUEST_MASK);
+ r = kvm_deassign_irq(kvm, match, irq_type);
out:
mutex_unlock(&kvm->lock);
return r;
@@ -609,6 +696,10 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
if (!match->pci_saved_state)
printk(KERN_DEBUG "%s: Couldn't store %s saved state\n",
__func__, dev_name(&dev->dev));
+
+ if (!pci_intx_mask_supported(dev))
+ assigned_dev->flags &= ~KVM_DEV_ASSIGN_PCI_2_3;
+
match->assigned_dev_id = assigned_dev->assigned_dev_id;
match->host_segnr = assigned_dev->segnr;
match->host_busnr = assigned_dev->busnr;
@@ -616,6 +707,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
match->flags = assigned_dev->flags;
match->dev = dev;
spin_lock_init(&match->intx_lock);
+ mutex_init(&match->intx_mask_lock);
match->irq_source_id = -1;
match->kvm = kvm;
match->ack_notifier.irq_acked = kvm_assigned_dev_ack_irq;
@@ -761,6 +853,56 @@ msix_entry_out:
}
#endif
+static int kvm_vm_ioctl_set_pci_irq_mask(struct kvm *kvm,
+ struct kvm_assigned_pci_dev *assigned_dev)
+{
+ int r = 0;
+ struct kvm_assigned_dev_kernel *match;
+
+ mutex_lock(&kvm->lock);
+
+ match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
+ assigned_dev->assigned_dev_id);
+ if (!match) {
+ r = -ENODEV;
+ goto out;
+ }
+
+ mutex_lock(&match->intx_mask_lock);
+
+ match->flags &= ~KVM_DEV_ASSIGN_MASK_INTX;
+ match->flags |= assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX;
+
+ if (match->irq_requested_type & KVM_DEV_IRQ_GUEST_INTX) {
+ if (assigned_dev->flags & KVM_DEV_ASSIGN_MASK_INTX) {
+ kvm_set_irq(match->kvm, match->irq_source_id,
+ match->guest_irq, 0);
+ /*
+ * Masking at hardware-level is performed on demand,
+ * i.e. when an IRQ actually arrives at the host.
+ */
+ } else {
+ /*
+ * Unmask the IRQ line. It may have been masked
+ * meanwhile if we aren't using PCI 2.3 INTx masking
+ * on the host side.
+ */
+ spin_lock_irq(&match->intx_lock);
+ if (match->host_irq_disabled) {
+ enable_irq(match->host_irq);
+ match->host_irq_disabled = false;
+ }
+ spin_unlock_irq(&match->intx_lock);
+ }
+ }
+
+ mutex_unlock(&match->intx_mask_lock);
+
+out:
+ mutex_unlock(&kvm->lock);
+ return r;
+}
+
long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
unsigned long arg)
{
@@ -868,6 +1010,15 @@ long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
break;
}
#endif
+ case KVM_ASSIGN_SET_INTX_MASK: {
+ struct kvm_assigned_pci_dev assigned_dev;
+
+ r = -EFAULT;
+ if (copy_from_user(&assigned_dev, argp, sizeof assigned_dev))
+ goto out;
+ r = kvm_vm_ioctl_set_pci_irq_mask(kvm, &assigned_dev);
+ break;
+ }
default:
r = -ENOTTY;
break;
@@ -875,4 +1026,3 @@ long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
out:
return r;
}
-
--
1.7.3.4
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