KVM: Merge kvm_ioapic_get_delivery_bitmask into kvm_get_intr_delivery_bitmask

Gleb fixed bitmap ops usage in kvm_ioapic_get_delivery_bitmask.

Sheng merged two functions, as well as fix several issues in kvm_get_intr_delivery_bitmask:
1. deliver_bitmask is a bitmap rather than a unsigned long intereger.
2. Lowest priority target bitmap wrong calculated by mistake.
3. Prevent potential NULL reference.
4. Declaration in include/kvm_host.h caused powerpc compilation warning.

Signed-off-by Gleb Natapov <[email protected]>

Signed-off-by Sheng Yang <[email protected]>

---
 include/linux/kvm_host.h |    3 ---
 virt/kvm/ioapic.c        |   39 ---------------------------------------
 virt/kvm/ioapic.h        |    5 +++--
 virt/kvm/irq_comm.c      |   42 ++++++++++++++++++++++++++++++++++++++----
 4 files changed, 41 insertions(+), 48 deletions(-)

include/linux/kvm_host.h +0 -3

index 3832243..fb60f31 100644
@@ -363,9 +363,6 @@ void kvm_unregister_irq_mask_notifier(struct kvm *kvm, int irq,
 				      struct kvm_irq_mask_notifier *kimn);
 void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask);
 
-void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
-				   union kvm_ioapic_redirect_entry *entry,
-				   unsigned long *deliver_bitmask);
 int kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level);
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin);
 void kvm_register_irq_ack_notifier(struct kvm *kvm,

virt/kvm/ioapic.c +0 -39

index 7c2cb2b..2c40ff8 100644
@@ -161,45 +161,6 @@ static void ioapic_inj_nmi(struct kvm_vcpu *vcpu)
 	kvm_vcpu_kick(vcpu);
 }
 
-void kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic *ioapic, u8 dest,
-				     u8 dest_mode, unsigned long *mask)
-{
-	int i;
-	struct kvm *kvm = ioapic->kvm;
-	struct kvm_vcpu *vcpu;
-
-	ioapic_debug("dest %d dest_mode %d\n", dest, dest_mode);
-
-	*mask = 0;
-	if (dest_mode == 0) {	/* Physical mode. */
-		if (dest == 0xFF) {	/* Broadcast. */
-			for (i = 0; i < KVM_MAX_VCPUS; ++i)
-				if (kvm->vcpus[i] && kvm->vcpus[i]->arch.apic)
-					*mask |= 1 << i;
-			return;
-		}
-		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
-			vcpu = kvm->vcpus[i];
-			if (!vcpu)
-				continue;
-			if (kvm_apic_match_physical_addr(vcpu->arch.apic, dest)) {
-				if (vcpu->arch.apic)
-					*mask = 1 << i;
-				break;
-			}
-		}
-	} else if (dest != 0)	/* Logical mode, MDA non-zero. */
-		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
-			vcpu = kvm->vcpus[i];
-			if (!vcpu)
-				continue;
-			if (vcpu->arch.apic &&
-			    kvm_apic_match_logical_addr(vcpu->arch.apic, dest))
-				*mask |= 1 << vcpu->vcpu_id;
-		}
-	ioapic_debug("mask %x\n", *mask);
-}
-
 static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 {
 	union kvm_ioapic_redirect_entry entry = ioapic->redirtbl[irq];

virt/kvm/ioapic.h +3 -2

index 7275f87..c8032ab 100644
@@ -70,7 +70,8 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode);
 int kvm_ioapic_init(struct kvm *kvm);
 int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
 void kvm_ioapic_reset(struct kvm_ioapic *ioapic);
-void kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic *ioapic, u8 dest,
-				     u8 dest_mode, unsigned long *mask);
+void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
+				   union kvm_ioapic_redirect_entry *entry,
+				   unsigned long *deliver_bitmask);
 
 #endif

virt/kvm/irq_comm.c +0 -0

index d165e05..bb6c5d0 100644
@@ -47,15 +47,49 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
 				   union kvm_ioapic_redirect_entry *entry,

virt/kvm/irq_comm.c +26 -0

+		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+			vcpu = kvm->vcpus[i];
+			if (!vcpu)
+				continue;
+			if (kvm_apic_match_physical_addr(vcpu->arch.apic,
+					entry->fields.dest_id)) {
+				if (vcpu->arch.apic)
+					__set_bit(i, deliver_bitmask);
+				break;
+			}
+		}
+	} else if (entry->fields.dest_id != 0) /* Logical mode, MDA non-zero. */
+		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+			vcpu = kvm->vcpus[i];
+			if (!vcpu)
+				continue;
+			if (vcpu->arch.apic &&
+			    kvm_apic_match_logical_addr(vcpu->arch.apic,
+					entry->fields.dest_id))
+				__set_bit(i, deliver_bitmask);
+		}
+
 	switch (entry->fields.delivery_mode) {
 	case IOAPIC_LOWEST_PRIORITY:
+		/* Select one in deliver_bitmask */
 		vcpu = kvm_get_lowest_prio_vcpu(ioapic->kvm,
 				entry->fields.vector, deliver_bitmask);
+		bitmap_zero(deliver_bitmask, KVM_MAX_VCPUS);
+		if (!vcpu)
+			return;
 		__set_bit(vcpu->vcpu_id, deliver_bitmask);
 		break;
 	case IOAPIC_FIXED:

Quoted 110 lines · Sheng Yang

Gleb fixed bitmap ops usage in kvm_ioapic_get_delivery_bitmask.

Sheng merged two functions, as well as fix several issues in kvm_get_intr_delivery_bitmask:
1. deliver_bitmask is a bitmap rather than a unsigned long intereger.
2. Lowest priority target bitmap wrong calculated by mistake.
3. Prevent potential NULL reference.
4. Declaration in include/kvm_host.h caused powerpc compilation warning.

Signed-off-by Gleb Natapov <[email protected]>

Signed-off-by Sheng Yang <[email protected]>

---
 include/linux/kvm_host.h |    3 ---
 virt/kvm/ioapic.c        |   39 ---------------------------------------
 virt/kvm/ioapic.h        |    5 +++--
 virt/kvm/irq_comm.c      |   42

++++++++++++++++++++++++++++++++++++++---- 4 files changed, 41 insertions(+), 48 deletions(-)

include/linux/kvm_host.h +0 -3

index 3832243..fb60f31 100644
@@ -363,9 +363,6 @@ void kvm_unregister_irq_mask_notifier(struct kvm
 *kvm, int irq, struct kvm_irq_mask_notifier *kimn);
 void kvm_fire_mask_notifiers(struct kvm *kvm, int irq, bool mask);
 
-void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
-				   union kvm_ioapic_redirect_entry *entry,
-				   unsigned long *deliver_bitmask);
 int kvm_set_irq(struct kvm *kvm, int irq_source_id, int irq, int level);
 void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned
 pin); void kvm_register_irq_ack_notifier(struct kvm *kvm,

virt/kvm/ioapic.c +0 -39

index 7c2cb2b..2c40ff8 100644
@@ -161,45 +161,6 @@ static void ioapic_inj_nmi(struct kvm_vcpu *vcpu)
 	kvm_vcpu_kick(vcpu);
 }
 
-void kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic *ioapic, u8 dest,
-				     u8 dest_mode, unsigned long *mask)
-{
-	int i;
-	struct kvm *kvm = ioapic->kvm;
-	struct kvm_vcpu *vcpu;
-
-	ioapic_debug("dest %d dest_mode %d\n", dest, dest_mode);
-
-	*mask = 0;
-	if (dest_mode == 0) {	/* Physical mode. */
-		if (dest == 0xFF) {	/* Broadcast. */
-			for (i = 0; i < KVM_MAX_VCPUS; ++i)
-				if (kvm->vcpus[i] && kvm->vcpus[i]->arch.apic)
-					*mask |= 1 << i;
-			return;
-		}
-		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
-			vcpu = kvm->vcpus[i];
-			if (!vcpu)
-				continue;
-			if (kvm_apic_match_physical_addr(vcpu->arch.apic, dest)) {
-				if (vcpu->arch.apic)
-					*mask = 1 << i;
-				break;
-			}
-		}
-	} else if (dest != 0)	/* Logical mode, MDA non-zero. */
-		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
-			vcpu = kvm->vcpus[i];
-			if (!vcpu)
-				continue;
-			if (vcpu->arch.apic &&
-			    kvm_apic_match_logical_addr(vcpu->arch.apic, dest))
-				*mask |= 1 << vcpu->vcpu_id;
-		}
-	ioapic_debug("mask %x\n", *mask);
-}
-
 static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 {
 	union kvm_ioapic_redirect_entry entry = ioapic->redirtbl[irq];

virt/kvm/ioapic.h +3 -2

index 7275f87..c8032ab 100644
@@ -70,7 +70,8 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector,
 int trigger_mode); int kvm_ioapic_init(struct kvm *kvm);
 int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
 void kvm_ioapic_reset(struct kvm_ioapic *ioapic);
-void kvm_ioapic_get_delivery_bitmask(struct kvm_ioapic *ioapic, u8 dest,
-				     u8 dest_mode, unsigned long *mask);
+void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
+				   union kvm_ioapic_redirect_entry *entry,
+				   unsigned long *deliver_bitmask);
 
 #endif

virt/kvm/irq_comm.c +2 -0

index d165e05..bb6c5d0 100644
@@ -47,15 +47,49 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic
 *ioapic, union kvm_ioapic_redirect_entry *entry,
 				   unsigned long *deliver_bitmask)
 {
+	int i;
+	struct kvm *kvm = ioapic->kvm;
 	struct kvm_vcpu *vcpu;
 

virt/kvm/irq_comm.c void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic, · line 54

Quoted 4 lines

virt/kvm/irq_comm.c +1 -3

-	kvm_ioapic_get_delivery_bitmask(ioapic, entry->fields.dest_id,
-					entry->fields.dest_mode,
-					deliver_bitmask);
+	bitmap_zero(deliver_bitmask, KVM_MAX_VCPUS);

I think you can drop the zeroing from the callers?

Quoted 4 lines

virt/kvm/irq_comm.c +4 -0

+
+	if (entry->fields.dest_mode == 0) {	/* Physical mode. */
+		if (entry->fields.dest_id == 0xFF) {	/* Broadcast. */
+			for (i = 0; i < KVM_MAX_VCPUS; ++i)

virt/kvm/irq_comm.c void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic, · line 62

Quoted 4 lines

virt/kvm/irq_comm.c +4 -0

+				if (kvm->vcpus[i] && kvm->vcpus[i]->arch.apic)
+					__set_bit(i, deliver_bitmask);
+			return;
+		}

The spec says broadcast is not supported with lowest priority delivery mode, and that "must not be configured by software". I wonder what happens in HW if you do that.

Quoted 36 lines

virt/kvm/irq_comm.c +25 -0

+		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+			vcpu = kvm->vcpus[i];
+			if (!vcpu)
+				continue;
+			if (kvm_apic_match_physical_addr(vcpu->arch.apic,
+					entry->fields.dest_id)) {
+				if (vcpu->arch.apic)
+					__set_bit(i, deliver_bitmask);
+				break;
+			}
+		}
+	} else if (entry->fields.dest_id != 0) /* Logical mode, MDA non-zero.
 */ +		for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+			vcpu = kvm->vcpus[i];
+			if (!vcpu)
+				continue;
+			if (vcpu->arch.apic &&
+			    kvm_apic_match_logical_addr(vcpu->arch.apic,
+					entry->fields.dest_id))
+				__set_bit(i, deliver_bitmask);
+		}
+
 	switch (entry->fields.delivery_mode) {
 	case IOAPIC_LOWEST_PRIORITY:
+		/* Select one in deliver_bitmask */
 		vcpu = kvm_get_lowest_prio_vcpu(ioapic->kvm,
 				entry->fields.vector, deliver_bitmask);
+		bitmap_zero(deliver_bitmask, KVM_MAX_VCPUS);
+		if (!vcpu)
+			return;
 		__set_bit(vcpu->vcpu_id, deliver_bitmask);
 		break;
 	case IOAPIC_FIXED:

@@ -65,7 +99,7 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic
 *ioapic, if (printk_ratelimit())
 			printk(KERN_INFO "kvm: unsupported delivery mode %d\n",

virt/kvm/irq_comm.c void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic, · line 104

Quoted 5 lines

virt/kvm/irq_comm.c +1 -1

 				entry->fields.delivery_mode);
-		*deliver_bitmask = 0;
+		bitmap_zero(deliver_bitmask, KVM_MAX_VCPUS);
 	}
 }

Unrelated question, what was the issue (in detail) which caused this change again:

[kvm-devel] The SMP RHEL 5.1 PAE guest can't boot up issue
From:
"Yang, Sheng" <[email protected]>  (Intel)
To:
[email protected]
Date:
2008-02-22 16:57
I believe I have found the root cause of SMP RHEL5.1 PAE guest can't boot up issue. The problem was caused by kvm:6685637b211ad67bdce21bfd9f91bc888b3acb4f
"KVM: VMX: Ensure vcpu time stamp counter is monotonous" (It didn't take me much time to found the solution, but a lot of time to find the proper explanation...  :( )

As we guessed, the problem was the monotonous of TSC. I have traced to the 2.6.18 PAE guest kernel, and finally found it caused by a overflow in the loop of function update_wall_timer()(kernel/timer.c), when using TSC as clocksource by default.

The reason is that the patch "KVM: VMX: Ensure vcpu time stamp counter is monotonous" bring big gap between different VCPUs (error between TSC_OFFSETs). Though I have proved that the patch can ensure the monotonous on each VCPU (which rejected my first thought...), the patch have 2 problems:

1. It have accumulated the error. Each vcpu's TSC is monotonous, but get slower and slower, compared to the host. That's because the TSC is very accuracy and the interval between reading TSC is big. But this is not very critical.

2. The critical one. In normal condition, VCPU0 migrated much more frequently than other VCPUs. And the patch add more "delta" (always negative if host TSC is stable) to TSC_OFFSET each
time migrated. Then after boot for a while, VCPU0 became much slower than others (In my test, VCPU0 was migrated about two times than the others, and easily to be more than 100k cycles slower). In the guest kernel, clocksource TSC is global variable, the variable "cycle_last" may got the VCPU1's TSC value, then turn to VCPU0. For VCPU0's TSC_OFFSET is smaller than VCPU1's, so it's possible to got the "cycle_last" (from VCPU1) bigger than current TSC value (from VCPU0) in next tick. Then "u64 offset = clocksource_read() - cycle_last" overflowed and caused the "infinite" loop. And it can also explained why Marcelo's patch don't work - it just reduce the rate of gap increasing.

The freezing didn't happen when using userspace IOAPIC, just because the qemu APIC didn't implement real LOWPRI(or round_robin) to choose CPU for delivery. It choose VCPU0 everytime if possible, so CPU1 in guest won't update cycle_last. :(

This freezing only occurred on RHEL5/5.1 pae (kernel 2.6.18), because of they set IO-APIC IRQ0's dest_mask to 0x3 (with 2 vcpus) and dest_mode as LOWEST_PRIOITY, then other vcpus had chance to modify "cycle_last". In contrast, RHEL5/5.1 32e set IRQ0's dest_mode as FIXED, to CPU0, then don't have this problem. So does RHEL4(kernel 2.6.9).

I don't know if the patch was still needed now, since it was posted long ago(I don't know which issue it solved). I'd like to post a revert patch if necessary.

Quoted 4 lines

The spec says broadcast is not supported with lowest priority delivery mode, and that "must not be configured by software". I wonder what happens in HW if you do that.

Um.. So you mean to prohibit this kind of action? OK.

Quoted 2 lines

Unrelated question, what was the issue (in detail) which caused this change again:

I have dig out my old post (I thought you are also involved :) )

Hi Sheng,

Quoted 5 lines

Quoted 3 lines

The spec says broadcast is not supported with lowest priority delivery mode, and that "must not be configured by software". I wonder what happens in HW if you do that.

Um.. So you mean to prohibit this kind of action? OK.

No, I'm just wondering what the HW does, and what are the implications of the (supposedly) different behaviour KVM emulates.

Quoted 4 lines

Quoted 2 lines

Unrelated question, what was the issue (in detail) which caused this change again:

I have dig out my old post (I thought you are also involved :) )

Short memory :)

Thanks, will read tomorrow.

Gleb fixed bitmap ops usage in kvm_ioapic_get_delivery_bitmask.

Sheng merged two functions, as well as fixed several issues in kvm_get_intr_delivery_bitmask
1. deliver_bitmask is a bitmap rather than a unsigned long intereger.
2. Lowest priority target bitmap wrong calculated by mistake.
3. Prevent potential NULL reference.
4. Declaration in include/kvm_host.h caused powerpc compilation warning.
5. Add warning for guest broadcast interrupt with lowest priority delivery mode.
6. Removed duplicate bitmap clean up in caller of kvm_get_intr_delivery_bitmask.

Signed-off-by Gleb Natapov <[email protected]>

Signed-off-by Sheng Yang <[email protected]>