On Tue, Jul 14, 2009 at 05:30:43PM +0300, Gleb Natapov wrote:
>
> Signed-off-by: Gleb Natapov <gleb@xxxxxxxxxx>
> ---
> arch/ia64/kvm/kvm-ia64.c | 27 ++++++++++++++++++------
> arch/x86/kvm/lapic.c | 5 +---
> arch/x86/kvm/x86.c | 30 ++++++++++++++++++---------
> virt/kvm/ioapic.c | 50 ++++++++++++++++++++++++++++-----------------
> virt/kvm/ioapic.h | 1 +
> 5 files changed, 73 insertions(+), 40 deletions(-)
>
> diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
> index 0ad09f0..dd7ef2d 100644
> --- a/arch/ia64/kvm/kvm-ia64.c
> +++ b/arch/ia64/kvm/kvm-ia64.c
> @@ -850,9 +850,16 @@ static int kvm_vm_ioctl_get_irqchip(struct kvm *kvm,
>
> r = 0;
> switch (chip->chip_id) {
> - case KVM_IRQCHIP_IOAPIC:
> - memcpy(&chip->chip.ioapic, ioapic_irqchip(kvm),
> - sizeof(struct kvm_ioapic_state));
> + case KVM_IRQCHIP_IOAPIC: {
> + struct kvm_ioapic *ioapic = ioapic_irqchip(kvm);
> + if (ioapic) {
> + spin_lock(&ioapic->lock);
> + memcpy(&chip->chip.ioapic, ioapic,
> + sizeof(struct kvm_ioapic_state));
> + spin_unlock(&ioapic->lock);
> + } else
> + r = -EINVAL;
> + }
> break;
> default:
> r = -EINVAL;
> @@ -867,10 +874,16 @@ static int kvm_vm_ioctl_set_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
>
> r = 0;
> switch (chip->chip_id) {
> - case KVM_IRQCHIP_IOAPIC:
> - memcpy(ioapic_irqchip(kvm),
> - &chip->chip.ioapic,
> - sizeof(struct kvm_ioapic_state));
> + case KVM_IRQCHIP_IOAPIC: {
> + struct kvm_ioapic *ioapic = ioapic_irqchip(kvm);
> + if (ioapic) {
> + spin_lock(&ioapic->lock);
> + memcpy(ioapic, &chip->chip.ioapic,
> + sizeof(struct kvm_ioapic_state));
> + spin_unlock(&ioapic->lock);
> + } else
> + r = -EINVAL;
> + }
> break;
> default:
> r = -EINVAL;
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index e2e2849..61ffcfc 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -471,11 +471,8 @@ static void apic_set_eoi(struct kvm_lapic *apic)
> trigger_mode = IOAPIC_LEVEL_TRIG;
> else
> trigger_mode = IOAPIC_EDGE_TRIG;
> - if (!(apic_get_reg(apic, APIC_SPIV) & APIC_SPIV_DIRECTED_EOI)) {
> - mutex_lock(&apic->vcpu->kvm->irq_lock);
> + if (!(apic_get_reg(apic, APIC_SPIV) & APIC_SPIV_DIRECTED_EOI))
> kvm_ioapic_update_eoi(apic->vcpu->kvm, vector, trigger_mode);
> - mutex_unlock(&apic->vcpu->kvm->irq_lock);
> - }
> }
>
> static void apic_send_ipi(struct kvm_lapic *apic)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 48567fa..de99b84 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2010,10 +2010,16 @@ static int kvm_vm_ioctl_get_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
> &pic_irqchip(kvm)->pics[1],
> sizeof(struct kvm_pic_state));
> break;
> - case KVM_IRQCHIP_IOAPIC:
> - memcpy(&chip->chip.ioapic,
> - ioapic_irqchip(kvm),
> - sizeof(struct kvm_ioapic_state));
> + case KVM_IRQCHIP_IOAPIC: {
> + struct kvm_ioapic *ioapic = ioapic_irqchip(kvm);
> + if (ioapic) {
> + spin_lock(&ioapic->lock);
> + memcpy(&chip->chip.ioapic, ioapic,
> + sizeof(struct kvm_ioapic_state));
> + spin_unlock(&ioapic->lock);
> + } else
> + r = -EINVAL;
> + }
> break;
> default:
> r = -EINVAL;
> @@ -2042,12 +2048,16 @@ static int kvm_vm_ioctl_set_irqchip(struct kvm *kvm, struct kvm_irqchip *chip)
> sizeof(struct kvm_pic_state));
> spin_unlock(&pic_irqchip(kvm)->lock);
> break;
> - case KVM_IRQCHIP_IOAPIC:
> - mutex_lock(&kvm->irq_lock);
> - memcpy(ioapic_irqchip(kvm),
> - &chip->chip.ioapic,
> - sizeof(struct kvm_ioapic_state));
> - mutex_unlock(&kvm->irq_lock);
> + case KVM_IRQCHIP_IOAPIC: {
> + struct kvm_ioapic *ioapic = ioapic_irqchip(kvm);
> + if (ioapic) {
> + spin_lock(&ioapic->lock);
> + memcpy(ioapic, &chip->chip.ioapic,
> + sizeof(struct kvm_ioapic_state));
> + spin_unlock(&ioapic->lock);
> + } else
> + r = -EINVAL;
> + }
> break;
> default:
> r = -EINVAL;
> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> index fa05f67..300ee3b 100644
> --- a/virt/kvm/ioapic.c
> +++ b/virt/kvm/ioapic.c
> @@ -182,6 +182,7 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
> union kvm_ioapic_redirect_entry entry;
> int ret = 1;
>
> + spin_lock(&ioapic->lock);
> if (irq >= 0 && irq < IOAPIC_NUM_PINS) {
> entry = ioapic->redirtbl[irq];
> level ^= entry.fields.polarity;
> @@ -196,34 +197,44 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
> }
> trace_kvm_ioapic_set_irq(entry.bits, irq, ret == 0);
> }
> + spin_unlock(&ioapic->lock);
> +
> return ret;
> }
>
> -static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int pin,
> - int trigger_mode)
> +static void __kvm_ioapic_update_eoi(struct kvm_ioapic *ioapic, int vector,
> + int trigger_mode)
> {
> - union kvm_ioapic_redirect_entry *ent;
> + int i;
> +
> + for (i = 0; i < IOAPIC_NUM_PINS; i++) {
> + union kvm_ioapic_redirect_entry *ent = &ioapic->redirtbl[i];
> +
> + if (ent->fields.vector != vector)
> + continue;
>
> - ent = &ioapic->redirtbl[pin];
> + /* ack notifier may call back into ioapic via kvm_set_irq() */
> + spin_unlock(&ioapic->lock);
> + kvm_notify_acked_irq(ioapic->kvm, KVM_IRQCHIP_IOAPIC, i);
> + spin_lock(&ioapic->lock);
While traversing the IOAPIC pins you drop the lock and acquire it again,
which is error prone: what if the redirection table is changed in
between, for example?
Also, irq_lock was held during ack and mask notifier callbacks, so they
(the callbacks) did not have to worry about concurrency.
You questioned the purpose of irq_lock earlier, and thats what it is:
synchronization between pic and ioapic blur at the irq notifiers.
Using RCU to synchronize ack/mask notifier list walk versus list
addition is good, but i'm not entirely sure that smaller locks like you
are proposing is a benefit long term (things become much more tricky).
Maybe it is the only way forward (and so you push this complexity to the
ack/mask notifiers), but i think it can be avoided until its proven that
there is contention on irq_lock (which is reduced by faster search).
> - kvm_notify_acked_irq(ioapic->kvm, KVM_IRQCHIP_IOAPIC, pin);
> + if (trigger_mode != IOAPIC_LEVEL_TRIG)
> + continue;
>
> - if (trigger_mode == IOAPIC_LEVEL_TRIG) {
> ASSERT(ent->fields.trig_mode == IOAPIC_LEVEL_TRIG);
> ent->fields.remote_irr = 0;
> - if (!ent->fields.mask && (ioapic->irr & (1 << pin)))
> - ioapic_service(ioapic, pin);
> + if (!ent->fields.mask && (ioapic->irr & (1 << i)))
> + ioapic_service(ioapic, i);
> }
> }
>
> void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode)
> {
> struct kvm_ioapic *ioapic = kvm->arch.vioapic;
> - int i;
>
> - for (i = 0; i < IOAPIC_NUM_PINS; i++)
> - if (ioapic->redirtbl[i].fields.vector == vector)
> - __kvm_ioapic_update_eoi(ioapic, i, trigger_mode);
> + spin_lock(&ioapic->lock);
> + __kvm_ioapic_update_eoi(ioapic, vector, trigger_mode);
> + spin_unlock(&ioapic->lock);
> }
>
> static inline struct kvm_ioapic *to_ioapic(struct kvm_io_device *dev)
> @@ -248,8 +259,8 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
> ioapic_debug("addr %lx\n", (unsigned long)addr);
> ASSERT(!(addr & 0xf)); /* check alignment */
>
> - mutex_lock(&ioapic->kvm->irq_lock);
> addr &= 0xff;
> + spin_lock(&ioapic->lock);
> switch (addr) {
> case IOAPIC_REG_SELECT:
> result = ioapic->ioregsel;
> @@ -263,6 +274,8 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
> result = 0;
> break;
> }
> + spin_unlock(&ioapic->lock);
> +
> switch (len) {
> case 8:
> *(u64 *) val = result;
> @@ -275,7 +288,6 @@ static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
> default:
> printk(KERN_WARNING "ioapic: wrong length %d\n", len);
> }
> - mutex_unlock(&ioapic->kvm->irq_lock);
> return 0;
> }
>
> @@ -291,15 +303,15 @@ static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
> (void*)addr, len, val);
> ASSERT(!(addr & 0xf)); /* check alignment */
>
> - mutex_lock(&ioapic->kvm->irq_lock);
> if (len == 4 || len == 8)
> data = *(u32 *) val;
> else {
> printk(KERN_WARNING "ioapic: Unsupported size %d\n", len);
> - goto unlock;
> + return 0;
> }
>
> addr &= 0xff;
> + spin_lock(&ioapic->lock);
> switch (addr) {
> case IOAPIC_REG_SELECT:
> ioapic->ioregsel = data;
> @@ -310,15 +322,14 @@ static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
> break;
> #ifdef CONFIG_IA64
> case IOAPIC_REG_EOI:
> - kvm_ioapic_update_eoi(ioapic->kvm, data, IOAPIC_LEVEL_TRIG);
> + __kvm_ioapic_update_eoi(ioapic, data, IOAPIC_LEVEL_TRIG);
> break;
> #endif
>
> default:
> break;
> }
> -unlock:
> - mutex_unlock(&ioapic->kvm->irq_lock);
> + spin_unlock(&ioapic->lock);
> return 0;
> }
>
> @@ -347,6 +358,7 @@ int kvm_ioapic_init(struct kvm *kvm)
> ioapic = kzalloc(sizeof(struct kvm_ioapic), GFP_KERNEL);
> if (!ioapic)
> return -ENOMEM;
> + spin_lock_init(&ioapic->lock);
> kvm->arch.vioapic = ioapic;
> kvm_ioapic_reset(ioapic);
> kvm_iodevice_init(&ioapic->dev, &ioapic_mmio_ops);
> diff --git a/virt/kvm/ioapic.h b/virt/kvm/ioapic.h
> index 7080b71..557107e 100644
> --- a/virt/kvm/ioapic.h
> +++ b/virt/kvm/ioapic.h
> @@ -44,6 +44,7 @@ struct kvm_ioapic {
> struct kvm_io_device dev;
> struct kvm *kvm;
> void (*ack_notifier)(void *opaque, int irq);
> + spinlock_t lock;
> };
>
> #ifdef DEBUG
> --
> 1.6.2.1
>
> --
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