On Tue, Feb 28, 2012 at 02:19:54PM +0100, Jan Kiszka wrote:
> 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>
Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
>
> Changes in v4:
> - Integrated doc changes as proposed by Alex
> - Fixed deassign_host_irq /wrt MSI
> - Fixed kvm_vm_ioctl_set_pci_irq_mask /wrt INTx unmasking of non-2.3
> devices
>
> Documentation/virtual/kvm/api.txt | 41 +++++++
> arch/x86/kvm/x86.c | 1 +
> include/linux/kvm.h | 6 +
> include/linux/kvm_host.h | 2 +
> virt/kvm/assigned-dev.c | 209 +++++++++++++++++++++++++++++++-----
> 5 files changed, 230 insertions(+), 29 deletions(-)
>
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index 59a3826..6386f8c 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.
> @@ -1441,6 +1449,39 @@ The "num_dirty" field is a performance hint for KVM to determine whether it
> should skip processing the bitmap and just invalidate everything. It must
> be set to the number of set bits in the bitmap.
>
> +4.60 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
> +
> +Allows userspace to mask PCI INTx interrupts from the assigned device. The
> +kernel will not deliver INTx interrupts to the guest between setting and
> +clearing of KVM_ASSIGN_SET_INTX_MASK via this interface. This enables use of
> +and emulation of PCI 2.3 INTx disable command register behavior.
> +
> +This may be used for both PCI 2.3 devices supporting INTx disable natively and
> +older devices lacking this support. Userspace is responsible for emulating the
> +read value of the INTx disable bit in the guest visible PCI command register.
> +When modifying the INTx disable state, userspace should precede updating the
> +physical device command register by calling this ioctl to inform the kernel of
> +the new intended INTx mask state.
> +
> +Note that the kernel uses the device INTx disable bit to internally manage the
> +device interrupt state for PCI 2.3 devices. Reads of this register may
> +therefore not match the expected value. Writes should always use the guest
> +intended INTx disable value rather than attempting to read-copy-update the
> +current physical device state. Races between user and kernel updates to the
> +INTx disable bit are handled lazily in the kernel. It's possible the device
> +may generate unintended interrupts, but they will not be injected into the
> +guest.
> +
> +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 c9d99e5..4e2088a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2143,6 +2143,7 @@ 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 acbe429..6c322a9 100644
> --- a/include/linux/kvm.h
> +++ b/include/linux/kvm.h
> @@ -588,6 +588,7 @@ 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
>
> @@ -784,6 +785,9 @@ 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
> @@ -857,6 +861,8 @@ struct kvm_s390_ucas_mapping {
> #define KVM_SET_ONE_REG _IOW(KVMIO, 0xac, struct kvm_one_reg)
>
> #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 355e445..94f239b 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -546,6 +546,7 @@ 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;
> @@ -555,6 +556,7 @@ 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 ece8061..08e0571 100644
> --- a/virt/kvm/assigned-dev.c
> +++ b/virt/kvm/assigned-dev.c
> @@ -55,22 +55,66 @@ 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)
> @@ -81,8 +125,7 @@ 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;
> @@ -98,15 +141,31 @@ 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,
> @@ -154,7 +213,15 @@ 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->irq_requested_type &
> + KVM_DEV_IRQ_HOST_INTX) &&
> + (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);
>
> @@ -235,15 +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;
> }
>
> @@ -260,8 +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;
> }
> @@ -319,7 +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
> @@ -331,7 +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
> @@ -365,6 +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;
> @@ -466,6 +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);
>
> @@ -474,7 +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;
> @@ -607,6 +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;
> @@ -614,6 +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;
> @@ -759,6 +853,55 @@ 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 if (!(assigned_dev->flags & KVM_DEV_ASSIGN_PCI_2_3)) {
> + /*
> + * Unmask the IRQ line if required. Unmasking at
> + * device level will be performed by user space.
> + */
> + 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)
> {
> @@ -866,6 +1009,15 @@ 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;
> @@ -873,4 +1025,3 @@ long kvm_vm_ioctl_assigned_device(struct kvm *kvm, unsigned ioctl,
> out:
> return r;
> }
> -
> --
> 1.7.3.4
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