Messages in this thread | | | Date | Thu, 11 Jun 2015 22:59:00 +0300 | From | Avi Kivity <> | Subject | Re: [v4 08/16] KVM: kvm-vfio: User API for IRQ forwarding |
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On 06/11/2015 01:51 PM, Feng Wu wrote: > From: Eric Auger <eric.auger@linaro.org> > > This patch adds and documents a new KVM_DEV_VFIO_DEVICE group > and 2 device attributes: KVM_DEV_VFIO_DEVICE_FORWARD_IRQ, > KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ. The purpose is to be able > to set a VFIO device IRQ as forwarded or not forwarded. > the command takes as argument a handle to a new struct named > kvm_vfio_dev_irq.
Is there no way to do this automatically? After all, vfio knows that a device interrupt is forwarded to some eventfd, and kvm knows that some eventfd is forwarded to a guest interrupt. If they compare notes through a central registry, they can figure out that the interrupt needs to be forwarded.
> Signed-off-by: Eric Auger <eric.auger@linaro.org> > --- > Documentation/virtual/kvm/devices/vfio.txt | 34 ++++++++++++++++++++++++------ > include/uapi/linux/kvm.h | 12 +++++++++++ > 2 files changed, 40 insertions(+), 6 deletions(-) > > diff --git a/Documentation/virtual/kvm/devices/vfio.txt b/Documentation/virtual/kvm/devices/vfio.txt > index ef51740..6186e6d 100644 > --- a/Documentation/virtual/kvm/devices/vfio.txt > +++ b/Documentation/virtual/kvm/devices/vfio.txt > @@ -4,15 +4,20 @@ VFIO virtual device > Device types supported: > KVM_DEV_TYPE_VFIO > > -Only one VFIO instance may be created per VM. The created device > -tracks VFIO groups in use by the VM and features of those groups > -important to the correctness and acceleration of the VM. As groups > -are enabled and disabled for use by the VM, KVM should be updated > -about their presence. When registered with KVM, a reference to the > -VFIO-group is held by KVM. > +Only one VFIO instance may be created per VM. > + > +The created device tracks VFIO groups in use by the VM and features > +of those groups important to the correctness and acceleration of > +the VM. As groups are enabled and disabled for use by the VM, KVM > +should be updated about their presence. When registered with KVM, > +a reference to the VFIO-group is held by KVM. > + > +The device also enables to control some IRQ settings of VFIO devices: > +forwarding/posting. > > Groups: > KVM_DEV_VFIO_GROUP > + KVM_DEV_VFIO_DEVICE > > KVM_DEV_VFIO_GROUP attributes: > KVM_DEV_VFIO_GROUP_ADD: Add a VFIO group to VFIO-KVM device tracking > @@ -20,3 +25,20 @@ KVM_DEV_VFIO_GROUP attributes: > > For each, kvm_device_attr.addr points to an int32_t file descriptor > for the VFIO group. > + > +KVM_DEV_VFIO_DEVICE attributes: > + KVM_DEV_VFIO_DEVICE_FORWARD_IRQ: set a VFIO device IRQ as forwarded > + KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ: set a VFIO device IRQ as not forwarded > + > +For each, kvm_device_attr.addr points to a kvm_vfio_dev_irq struct. > + > +When forwarded, a physical IRQ is completed by the guest and not by the > +host. This requires HW support in the interrupt controller. > + > +Forwarding can only be set when the corresponding VFIO IRQ is not masked > +(would it be through VFIO_DEVICE_SET_IRQS command or as a consequence of this > +IRQ being currently handled) or active at interrupt controller level. > +In such a situation, -EAGAIN is returned. It is advised to to set the > +forwarding before the VFIO signaling is set up, this avoids trial and errors. > + > +Unforwarding can happen at any time. > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h > index 4b60056..798f3e4 100644 > --- a/include/uapi/linux/kvm.h > +++ b/include/uapi/linux/kvm.h > @@ -999,6 +999,9 @@ struct kvm_device_attr { > #define KVM_DEV_VFIO_GROUP 1 > #define KVM_DEV_VFIO_GROUP_ADD 1 > #define KVM_DEV_VFIO_GROUP_DEL 2 > +#define KVM_DEV_VFIO_DEVICE 2 > +#define KVM_DEV_VFIO_DEVICE_FORWARD_IRQ 1 > +#define KVM_DEV_VFIO_DEVICE_UNFORWARD_IRQ 2 > > enum kvm_device_type { > KVM_DEV_TYPE_FSL_MPIC_20 = 1, > @@ -1018,6 +1021,15 @@ enum kvm_device_type { > KVM_DEV_TYPE_MAX, > }; > > +struct kvm_vfio_dev_irq { > + __u32 argsz; /* structure length */ > + __u32 fd; /* file descriptor of the VFIO device */ > + __u32 index; /* VFIO device IRQ index */ > + __u32 start; /* start of subindex range */ > + __u32 count; /* size of subindex range */ > + __u32 gsi[]; /* gsi, ie. virtual IRQ number */ > +}; > + > /* > * ioctls for VM fds > */
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