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Subject[KVM PATCH v7 1/2] KVM: make io_bus interface more robust
Date
Today kvm_io_bus_regsiter_dev() returns void and will internally BUG_ON if it
fails. We want to create dynamic MMIO/PIO entries driven from userspace later
in the series, so we need to enhance the code to be more robust with the
following changes:

1) Add a return value to the registration function
2) Fix up all the callsites to check the return code, handle any
failures, and percolate the error up to the caller.
3) Add an unregister function that collapses holes in the array

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
---
arch/x86/kvm/i8254.c | 22 ++++++++++++++++++++--
arch/x86/kvm/i8259.c | 9 ++++++++-
include/linux/kvm_host.h | 6 ++++--
virt/kvm/coalesced_mmio.c | 8 ++++++--
virt/kvm/ioapic.c | 9 +++++++--
virt/kvm/kvm_main.c | 30 ++++++++++++++++++++++++++++--
6 files changed, 73 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 331705f..1c41715 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -586,6 +586,7 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
{
struct kvm_pit *pit;
struct kvm_kpit_state *pit_state;
+ int ret;

pit = kzalloc(sizeof(struct kvm_pit), GFP_KERNEL);
if (!pit)
@@ -620,14 +621,31 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
kvm_register_irq_mask_notifier(kvm, 0, &pit->mask_notifier);

kvm_iodevice_init(&pit->dev, &pit_dev_ops);
- kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
+ ret = kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
+ if (ret < 0)
+ goto fail;

if (flags & KVM_PIT_SPEAKER_DUMMY) {
kvm_iodevice_init(&pit->speaker_dev, &speaker_dev_ops);
- kvm_io_bus_register_dev(&kvm->pio_bus, &pit->speaker_dev);
+ ret = kvm_io_bus_register_dev(&kvm->pio_bus,
+ &pit->speaker_dev);
+ if (ret < 0)
+ goto fail;
}

return pit;
+
+fail:
+ if (flags & KVM_PIT_SPEAKER_DUMMY)
+ kvm_io_bus_unregister_dev(&kvm->pio_bus, &pit->speaker_dev);
+
+ kvm_io_bus_unregister_dev(&kvm->pio_bus, &pit->dev);
+
+ if (pit->irq_source_id >= 0)
+ kvm_free_irq_source_id(kvm, pit->irq_source_id);
+
+ kfree(pit);
+ return NULL;
}

void kvm_free_pit(struct kvm *kvm)
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 148c52a..66e37c2 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -532,6 +532,8 @@ static const struct kvm_io_device_ops picdev_ops = {
struct kvm_pic *kvm_create_pic(struct kvm *kvm)
{
struct kvm_pic *s;
+ int ret;
+
s = kzalloc(sizeof(struct kvm_pic), GFP_KERNEL);
if (!s)
return NULL;
@@ -548,6 +550,11 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm)
* Initialize PIO device
*/
kvm_iodevice_init(&s->dev, &picdev_ops);
- kvm_io_bus_register_dev(&kvm->pio_bus, &s->dev);
+ ret = kvm_io_bus_register_dev(&kvm->pio_bus, &s->dev);
+ if (ret < 0) {
+ kfree(s);
+ return NULL;
+ }
+
return s;
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e4e78db..eafa2b3 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -61,8 +61,10 @@ void kvm_io_bus_init(struct kvm_io_bus *bus);
void kvm_io_bus_destroy(struct kvm_io_bus *bus);
struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
gpa_t addr, int len, int is_write);
-void kvm_io_bus_register_dev(struct kvm_io_bus *bus,
- struct kvm_io_device *dev);
+int kvm_io_bus_register_dev(struct kvm_io_bus *bus,
+ struct kvm_io_device *dev);
+void kvm_io_bus_unregister_dev(struct kvm_io_bus *bus,
+ struct kvm_io_device *dev);

struct kvm_vcpu {
struct kvm *kvm;
diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
index 397f419..3e89db8 100644
--- a/virt/kvm/coalesced_mmio.c
+++ b/virt/kvm/coalesced_mmio.c
@@ -94,6 +94,7 @@ static const struct kvm_io_device_ops coalesced_mmio_ops = {
int kvm_coalesced_mmio_init(struct kvm *kvm)
{
struct kvm_coalesced_mmio_dev *dev;
+ int ret;

dev = kzalloc(sizeof(struct kvm_coalesced_mmio_dev), GFP_KERNEL);
if (!dev)
@@ -102,9 +103,12 @@ int kvm_coalesced_mmio_init(struct kvm *kvm)
kvm_iodevice_init(&dev->dev, &coalesced_mmio_ops);
dev->kvm = kvm;
kvm->coalesced_mmio_dev = dev;
- kvm_io_bus_register_dev(&kvm->mmio_bus, &dev->dev);

- return 0;
+ ret = kvm_io_bus_register_dev(&kvm->mmio_bus, &dev->dev);
+ if (ret < 0)
+ kfree(dev);
+
+ return ret;
}

int kvm_vm_ioctl_register_coalesced_mmio(struct kvm *kvm,
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index d8b2eca..28adb05 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -335,6 +335,7 @@ static const struct kvm_io_device_ops ioapic_mmio_ops = {
int kvm_ioapic_init(struct kvm *kvm)
{
struct kvm_ioapic *ioapic;
+ int ret;

ioapic = kzalloc(sizeof(struct kvm_ioapic), GFP_KERNEL);
if (!ioapic)
@@ -343,7 +344,11 @@ int kvm_ioapic_init(struct kvm *kvm)
kvm_ioapic_reset(ioapic);
kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);
ioapic->kvm = kvm;
- kvm_io_bus_register_dev(&kvm->mmio_bus, &ioapic->dev);
- return 0;
+
+ ret = kvm_io_bus_register_dev(&kvm->mmio_bus, &ioapic->dev);
+ if (ret < 0)
+ kfree(ioapic);
+
+ return ret;
}

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9fab08e..b2cd59c 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2481,11 +2481,37 @@ struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
return NULL;
}

-void kvm_io_bus_register_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev)
+/* assumes kvm->lock held */
+int kvm_io_bus_register_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev)
{
- BUG_ON(bus->dev_count > (NR_IOBUS_DEVS-1));
+ if (bus->dev_count > (NR_IOBUS_DEVS-1))
+ return -ENOSPC;

bus->devs[bus->dev_count++] = dev;
+
+ return 0;
+}
+
+/* assumes kvm->lock held */
+void kvm_io_bus_unregister_dev(struct kvm_io_bus *bus,
+ struct kvm_io_device *dev)
+{
+ int i;
+
+ for (i = 0; i < bus->dev_count; i++) {
+
+ if (bus->devs[i] == dev) {
+ int j;
+
+ /* backfill the hole */
+ for (j = i; j < bus->dev_count-1; j++)
+ bus->devs[j] = bus->devs[j+1];
+
+ bus->dev_count--;
+
+ break;
+ }
+ }
}

static struct notifier_block kvm_cpu_notifier = {


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