On 12/04/2010 01:37 AM, Jan Kiszka wrote:
From: Jan Kiszka<jan.kiszka@xxxxxxxxxxx>
PCI 2.3 allows to generically disable IRQ sources at device level. This
enables us to share IRQs of such devices on the host side when passing
them to a guest.
However, IRQ disabling via the PCI config space is more costly than
masking the line via disable_irq. Therefore we register an IRQ sharing
notifier and switch between line and device level disabling on demand.
This feature is optional, user space has to request it explicitly as it
also has to inform us about its view of PCI_COMMAND_INTX_DISABLE. That
way, we can avoid unmasking the interrupt and signaling it if the guest
masked it via the PCI config space.
diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index e1a9297..5e164db 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -1112,6 +1112,14 @@ 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, but only if IRQ sharing with other
+assigned or host devices requires it. KVM_DEV_ASSIGN_MASK_INTX specifies the
+guest's view on the INTx mask, see KVM_ASSIGN_SET_INTX_MASK for details.
4.48 KVM_DEASSIGN_PCI_DEVICE
@@ -1263,6 +1271,23 @@ struct kvm_assigned_msix_entry {
__u16 padding[3];
};
+4.54 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
+
+Informs the kernel about the guest's view on the INTx mask. As long as the
+guest masks the legacy INTx, the kernel will refrain from unmasking it at
+hardware level and will not assert the guest's IRQ line. User space is still
+responsible for applying this state to the assigned device's real config space.
What's the protocol for doing this? I suppose userspace has to disable
interrupts, ioctl(SET_INTX_MASK, masked), ..., ioctl(SET_INTX_MASK,
unmasked), enable interrupts?
Isn't there a race window between the two operations?
Maybe we should give the kernel full ownership of that bit.
+
+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.
+
--
error compiling committee.c: too many arguments to function
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