[PATCH 0/3] KVM: x86: clean up interrupt injection

[PATCH 0/3] KVM: x86: clean up interrupt injection

[Paolo Bonzini]

Legacy device assignment attempted to only do lightweight work when
injecting interrupts from atomic context.  This will be important
if we let VFIO inject interrupts from a non-threaded interrupt handler.
This series lets irqfd ditinguish between atomic-context and generic
interrupt injection.

Patch 1 is the real change, everything else cleans up what's left behind.

Paolo

Paolo Bonzini (3):
  KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic
  KVM: device assignment: remove pointless #ifdefs
  KVM: x86: move kvm_set_irq_inatomic to legacy device assignment

 arch/x86/kvm/assigned-dev.c | 62 +++++++++++++++++++++++++++------------------
 arch/x86/kvm/irq_comm.c     | 44 +++++---------------------------
 include/linux/kvm_host.h    |  8 +++---
 virt/kvm/eventfd.c          | 11 +++-----
 4 files changed, 50 insertions(+), 75 deletions(-)

-- 
1.8.3.1

[PATCH 1/3] KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic

[Paolo Bonzini]

We do not want to do too much work in atomic context, in particular
not walking all the VCPUs of the virtual machine.  So we want
to distinguish the architecture-specific injection function for irqfd
from kvm_set_msi.  Since it's still empty, reuse the newly added
kvm_arch_set_irq and rename it to kvm_arch_set_irq_inatomic.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/irq_comm.c  | 14 ++++++++------
 include/linux/kvm_host.h |  7 +++----
 virt/kvm/eventfd.c       | 11 ++++-------
 3 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 8f4499c7ffc1..26d830c1b7af 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -124,12 +124,16 @@ int kvm_set_msi(struct kvm_kernel_irq_routing_entry *e,
 }
 
 
-static int kvm_set_msi_inatomic(struct kvm_kernel_irq_routing_entry *e,
-			 struct kvm *kvm)
+int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
+			      struct kvm *kvm, int irq_source_id, int level,
+			      bool line_status)
 {
 	struct kvm_lapic_irq irq;
 	int r;
 
+	if (unlikely(e->type != KVM_IRQ_ROUTING_MSI))
+		return -EWOULDBLOCK;
+
 	kvm_set_msi_irq(e, &irq);
 
 	if (kvm_irq_delivery_to_apic_fast(kvm, NULL, &irq, &r, NULL))
@@ -165,10 +169,8 @@ int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level)
 	idx = srcu_read_lock(&kvm->irq_srcu);
 	if (kvm_irq_map_gsi(kvm, entries, irq) > 0) {
 		e = &entries[0];
-		if (likely(e->type == KVM_IRQ_ROUTING_MSI))
-			ret = kvm_set_msi_inatomic(e, kvm);
-		else
-			ret = -EWOULDBLOCK;
+		ret = kvm_arch_set_irq_inatomic(e, kvm, irq_source_id,
+						irq, level);
 	}
 	srcu_read_unlock(&kvm->irq_srcu, idx);
 	return ret;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index eba9caebc9c1..42fb9e089fc9 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -828,10 +828,9 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level,
 int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level);
 int kvm_set_msi(struct kvm_kernel_irq_routing_entry *irq_entry, struct kvm *kvm,
 		int irq_source_id, int level, bool line_status);
-
-int kvm_arch_set_irq(struct kvm_kernel_irq_routing_entry *irq, struct kvm *kvm,
-		     int irq_source_id, int level, bool line_status);
-
+int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
+			       struct kvm *kvm, int irq_source_id,
+			       int level, bool line_status);
 bool kvm_irq_has_notifier(struct kvm *kvm, unsigned irqchip, unsigned pin);
 void kvm_notify_acked_gsi(struct kvm *kvm, int gsi);
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin);
diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index e29fd2640709..46dbc0a7dfc1 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -171,7 +171,7 @@ irqfd_deactivate(struct kvm_kernel_irqfd *irqfd)
 	queue_work(irqfd_cleanup_wq, &irqfd->shutdown);
 }
 
-int __attribute__((weak)) kvm_arch_set_irq(
+int __attribute__((weak)) kvm_arch_set_irq_inatomic(
 				struct kvm_kernel_irq_routing_entry *irq,
 				struct kvm *kvm, int irq_source_id,
 				int level,
@@ -201,12 +201,9 @@ irqfd_wakeup(wait_queue_t *wait, unsigned mode, int sync, void *key)
 			irq = irqfd->irq_entry;
 		} while (read_seqcount_retry(&irqfd->irq_entry_sc, seq));
 		/* An event has been signaled, inject an interrupt */
-		if (irq.type == KVM_IRQ_ROUTING_MSI)
-			kvm_set_msi(&irq, kvm, KVM_USERSPACE_IRQ_SOURCE_ID, 1,
-					false);
-		else if (kvm_arch_set_irq(&irq, kvm,
-					  KVM_USERSPACE_IRQ_SOURCE_ID, 1,
-					  false) == -EWOULDBLOCK)
+		if (kvm_arch_set_irq_inatomic(&irq, kvm,
+					      KVM_USERSPACE_IRQ_SOURCE_ID, 1,
+					      false) == -EWOULDBLOCK)
 			schedule_work(&irqfd->inject);
 		srcu_read_unlock(&kvm->irq_srcu, idx);
 	}
-- 
1.8.3.1

Re: [PATCH 1/3] KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic

[Radim Krcmar]

2015-11-02 13:21+0100, Paolo Bonzini:
> We do not want to do too much work in atomic context, in particular
> not walking all the VCPUs of the virtual machine.  So we want
> to distinguish the architecture-specific injection function for irqfd
> from kvm_set_msi.  Since it's still empty, reuse the newly added
> kvm_arch_set_irq and rename it to kvm_arch_set_irq_inatomic.

kvm/queue uses kvm_arch_set_irq since b7184313f4b9 ("kvm/x86: Hyper-V
synthetic interrupt controller").

Is synic going to be dropped before this patch is merged?

Re: [PATCH 1/3] KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic

[Paolo Bonzini]

On 02/11/2015 15:59, Radim Krcmar wrote:
> > We do not want to do too much work in atomic context, in particular
> > not walking all the VCPUs of the virtual machine.  So we want
> > to distinguish the architecture-specific injection function for irqfd
> > from kvm_set_msi.  Since it's still empty, reuse the newly added
> > kvm_arch_set_irq and rename it to kvm_arch_set_irq_inatomic.
> 
> kvm/queue uses kvm_arch_set_irq since b7184313f4b9 ("kvm/x86: Hyper-V
> synthetic interrupt controller").
> 
> Is synic going to be dropped before this patch is merged?

Yes.  Both because the Virtuozzo people confirmed that kvm_arch_set_irq
isn't needed for synic, and because synic is currently broken with APICv.

Paolo

Re: [PATCH 1/3] KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic

[Radim Krcmar]

2015-11-02 17:08+0100, Paolo Bonzini:
> On 02/11/2015 15:59, Radim Krcmar wrote:
>>> We do not want to do too much work in atomic context, in particular
>>> not walking all the VCPUs of the virtual machine.  So we want
>>> to distinguish the architecture-specific injection function for irqfd
>>> from kvm_set_msi.  Since it's still empty, reuse the newly added
>>> kvm_arch_set_irq and rename it to kvm_arch_set_irq_inatomic.
>> 
>> kvm/queue uses kvm_arch_set_irq since b7184313f4b9 ("kvm/x86: Hyper-V
>> synthetic interrupt controller").
>> 
>> Is synic going to be dropped before this patch is merged?
> 
> Yes.  Both because the Virtuozzo people confirmed that kvm_arch_set_irq
> isn't needed for synic, and because synic is currently broken with APICv.

Thanks.

(We can add direct delivery for |online vcpus| < X if performance with
 low number of VCPUs happens to regress because of the schedule_work,)

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>

[2/3] and [3/3] are good too.

Re: [PATCH 1/3] KVM: x86: merge kvm_arch_set_irq with kvm_set_msi_inatomic

[Paolo Bonzini]

On 02/11/2015 18:01, Radim Krcmar wrote:
>> > Yes.  Both because the Virtuozzo people confirmed that kvm_arch_set_irq
>> > isn't needed for synic, and because synic is currently broken with APICv.
> Thanks.
> 
> (We can add direct delivery for |online vcpus| < X if performance with
>  low number of VCPUs happens to regress because of the schedule_work,)

Yeah, we will change the VFIO interrupt handler to non-threaded, which
will do more or less the same (what you lose now through schedule_work,
you will recoup by doing things directly in the ISR).

Paolo

[PATCH 2/3] KVM: device assignment: remove pointless #ifdefs

[Paolo Bonzini]

The symbols are always defined.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/assigned-dev.c | 25 -------------------------
 1 file changed, 25 deletions(-)

diff --git a/arch/x86/kvm/assigned-dev.c b/arch/x86/kvm/assigned-dev.c
index d090ecf08809..1c17ee807ef7 100644
--- a/arch/x86/kvm/assigned-dev.c
+++ b/arch/x86/kvm/assigned-dev.c
@@ -131,7 +131,6 @@ static irqreturn_t kvm_assigned_dev_thread_intx(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-#ifdef __KVM_HAVE_MSI
 static irqreturn_t kvm_assigned_dev_msi(int irq, void *dev_id)
 {
 	struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
@@ -150,9 +149,7 @@ static irqreturn_t kvm_assigned_dev_thread_msi(int irq, void *dev_id)
 
 	return IRQ_HANDLED;
 }
-#endif
 
-#ifdef __KVM_HAVE_MSIX
 static irqreturn_t kvm_assigned_dev_msix(int irq, void *dev_id)
 {
 	struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
@@ -183,7 +180,6 @@ static irqreturn_t kvm_assigned_dev_thread_msix(int irq, void *dev_id)
 
 	return IRQ_HANDLED;
 }
-#endif
 
 /* Ack the irq line for an assigned device */
 static void kvm_assigned_dev_ack_irq(struct kvm_irq_ack_notifier *kian)
@@ -386,7 +382,6 @@ static int assigned_device_enable_host_intx(struct kvm *kvm,
 	return 0;
 }
 
-#ifdef __KVM_HAVE_MSI
 static int assigned_device_enable_host_msi(struct kvm *kvm,
 					   struct kvm_assigned_dev_kernel *dev)
 {
@@ -408,9 +403,7 @@ static int assigned_device_enable_host_msi(struct kvm *kvm,
 
 	return 0;
 }
-#endif
 
-#ifdef __KVM_HAVE_MSIX
 static int assigned_device_enable_host_msix(struct kvm *kvm,
 					    struct kvm_assigned_dev_kernel *dev)
 {
@@ -443,8 +436,6 @@ err:
 	return r;
 }
 
-#endif
-
 static int assigned_device_enable_guest_intx(struct kvm *kvm,
 				struct kvm_assigned_dev_kernel *dev,
 				struct kvm_assigned_irq *irq)
@@ -454,7 +445,6 @@ static int assigned_device_enable_guest_intx(struct kvm *kvm,
 	return 0;
 }
 
-#ifdef __KVM_HAVE_MSI
 static int assigned_device_enable_guest_msi(struct kvm *kvm,
 			struct kvm_assigned_dev_kernel *dev,
 			struct kvm_assigned_irq *irq)
@@ -463,9 +453,7 @@ static int assigned_device_enable_guest_msi(struct kvm *kvm,
 	dev->ack_notifier.gsi = -1;
 	return 0;
 }
-#endif
 
-#ifdef __KVM_HAVE_MSIX
 static int assigned_device_enable_guest_msix(struct kvm *kvm,
 			struct kvm_assigned_dev_kernel *dev,
 			struct kvm_assigned_irq *irq)
@@ -474,7 +462,6 @@ static int assigned_device_enable_guest_msix(struct kvm *kvm,
 	dev->ack_notifier.gsi = -1;
 	return 0;
 }
-#endif
 
 static int assign_host_irq(struct kvm *kvm,
 			   struct kvm_assigned_dev_kernel *dev,
@@ -492,16 +479,12 @@ static int assign_host_irq(struct kvm *kvm,
 	case KVM_DEV_IRQ_HOST_INTX:
 		r = assigned_device_enable_host_intx(kvm, dev);
 		break;
-#ifdef __KVM_HAVE_MSI
 	case KVM_DEV_IRQ_HOST_MSI:
 		r = assigned_device_enable_host_msi(kvm, dev);
 		break;
-#endif
-#ifdef __KVM_HAVE_MSIX
 	case KVM_DEV_IRQ_HOST_MSIX:
 		r = assigned_device_enable_host_msix(kvm, dev);
 		break;
-#endif
 	default:
 		r = -EINVAL;
 	}
@@ -534,16 +517,12 @@ static int assign_guest_irq(struct kvm *kvm,
 	case KVM_DEV_IRQ_GUEST_INTX:
 		r = assigned_device_enable_guest_intx(kvm, dev, irq);
 		break;
-#ifdef __KVM_HAVE_MSI
 	case KVM_DEV_IRQ_GUEST_MSI:
 		r = assigned_device_enable_guest_msi(kvm, dev, irq);
 		break;
-#endif
-#ifdef __KVM_HAVE_MSIX
 	case KVM_DEV_IRQ_GUEST_MSIX:
 		r = assigned_device_enable_guest_msix(kvm, dev, irq);
 		break;
-#endif
 	default:
 		r = -EINVAL;
 	}
@@ -826,7 +805,6 @@ out:
 }
 
 
-#ifdef __KVM_HAVE_MSIX
 static int kvm_vm_ioctl_set_msix_nr(struct kvm *kvm,
 				    struct kvm_assigned_msix_nr *entry_nr)
 {
@@ -906,7 +884,6 @@ msix_entry_out:
 
 	return r;
 }
-#endif
 
 static int kvm_vm_ioctl_set_pci_irq_mask(struct kvm *kvm,
 		struct kvm_assigned_pci_dev *assigned_dev)
@@ -1012,7 +989,6 @@ long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
 			goto out;
 		break;
 	}
-#ifdef __KVM_HAVE_MSIX
 	case KVM_ASSIGN_SET_MSIX_NR: {
 		struct kvm_assigned_msix_nr entry_nr;
 		r = -EFAULT;
@@ -1033,7 +1009,6 @@ long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
 			goto out;
 		break;
 	}
-#endif
 	case KVM_ASSIGN_SET_INTX_MASK: {
 		struct kvm_assigned_pci_dev assigned_dev;
 
-- 
1.8.3.1

[PATCH 3/3] KVM: x86: move kvm_set_irq_inatomic to legacy device assignment

[Paolo Bonzini]

The function is not used outside device assignment, and
kvm_arch_set_irq_inatomic has a different prototype.  Move it here and
make it static to avoid confusion.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/assigned-dev.c | 37 +++++++++++++++++++++++++++++++++++++
 arch/x86/kvm/irq_comm.c     | 34 ----------------------------------
 include/linux/kvm_host.h    |  1 -
 3 files changed, 37 insertions(+), 35 deletions(-)

diff --git a/arch/x86/kvm/assigned-dev.c b/arch/x86/kvm/assigned-dev.c
index 1c17ee807ef7..9dc091acd5fb 100644
--- a/arch/x86/kvm/assigned-dev.c
+++ b/arch/x86/kvm/assigned-dev.c
@@ -21,6 +21,7 @@
 #include <linux/fs.h>
 #include "irq.h"
 #include "assigned-dev.h"
+#include "trace/events/kvm.h"
 
 struct kvm_assigned_dev_kernel {
 	struct kvm_irq_ack_notifier ack_notifier;
@@ -131,6 +132,42 @@ static irqreturn_t kvm_assigned_dev_thread_intx(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
+/*
+ * Deliver an IRQ in an atomic context if we can, or return a failure,
+ * user can retry in a process context.
+ * Return value:
+ *  -EWOULDBLOCK - Can't deliver in atomic context: retry in a process context.
+ *  Other values - No need to retry.
+ */
+static int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq,
+				int level)
+{
+	struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS];
+	struct kvm_kernel_irq_routing_entry *e;
+	int ret = -EINVAL;
+	int idx;
+
+	trace_kvm_set_irq(irq, level, irq_source_id);
+
+	/*
+	 * Injection into either PIC or IOAPIC might need to scan all CPUs,
+	 * which would need to be retried from thread context;  when same GSI
+	 * is connected to both PIC and IOAPIC, we'd have to report a
+	 * partial failure here.
+	 * Since there's no easy way to do this, we only support injecting MSI
+	 * which is limited to 1:1 GSI mapping.
+	 */
+	idx = srcu_read_lock(&kvm->irq_srcu);
+	if (kvm_irq_map_gsi(kvm, entries, irq) > 0) {
+		e = &entries[0];
+		ret = kvm_arch_set_irq_inatomic(e, kvm, irq_source_id,
+						irq, level);
+	}
+	srcu_read_unlock(&kvm->irq_srcu, idx);
+	return ret;
+}
+
+
 static irqreturn_t kvm_assigned_dev_msi(int irq, void *dev_id)
 {
 	struct kvm_assigned_dev_kernel *assigned_dev = dev_id;
diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
index 26d830c1b7af..35b0dfb7f704 100644
--- a/arch/x86/kvm/irq_comm.c
+++ b/arch/x86/kvm/irq_comm.c
@@ -142,40 +142,6 @@ int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
 		return -EWOULDBLOCK;
 }
 
-/*
- * Deliver an IRQ in an atomic context if we can, or return a failure,
- * user can retry in a process context.
- * Return value:
- *  -EWOULDBLOCK - Can't deliver in atomic context: retry in a process context.
- *  Other values - No need to retry.
- */
-int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level)
-{
-	struct kvm_kernel_irq_routing_entry entries[KVM_NR_IRQCHIPS];
-	struct kvm_kernel_irq_routing_entry *e;
-	int ret = -EINVAL;
-	int idx;
-
-	trace_kvm_set_irq(irq, level, irq_source_id);
-
-	/*
-	 * Injection into either PIC or IOAPIC might need to scan all CPUs,
-	 * which would need to be retried from thread context;  when same GSI
-	 * is connected to both PIC and IOAPIC, we'd have to report a
-	 * partial failure here.
-	 * Since there's no easy way to do this, we only support injecting MSI
-	 * which is limited to 1:1 GSI mapping.
-	 */
-	idx = srcu_read_lock(&kvm->irq_srcu);
-	if (kvm_irq_map_gsi(kvm, entries, irq) > 0) {
-		e = &entries[0];
-		ret = kvm_arch_set_irq_inatomic(e, kvm, irq_source_id,
-						irq, level);
-	}
-	srcu_read_unlock(&kvm->irq_srcu, idx);
-	return ret;
-}
-
 int kvm_request_irq_source_id(struct kvm *kvm)
 {
 	unsigned long *bitmap = &kvm->arch.irq_sources_bitmap;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 42fb9e089fc9..e5d517a9d922 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -825,7 +825,6 @@ int kvm_irq_map_chip_pin(struct kvm *kvm, unsigned irqchip, unsigned pin);
 
 int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level,
 		bool line_status);
-int kvm_set_irq_inatomic(struct kvm *kvm, int irq_source_id, u32 irq, int level);
 int kvm_set_msi(struct kvm_kernel_irq_routing_entry *irq_entry, struct kvm *kvm,
 		int irq_source_id, int level, bool line_status);
 int kvm_arch_set_irq_inatomic(struct kvm_kernel_irq_routing_entry *e,
-- 
1.8.3.1