On 11/08/2010 01:21 PM, Jan Kiszka wrote:
PCI 2.3 allows to generically disable IRQ sources at device level. This
enables us to share IRQs of such devices between on the host side when
passing them to a guest. This feature 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 PCI config space.
It's a pity this cannot be done transparently. We could detect multiple
devices sharing the line, but what about PCI_COMMAND_INTX_DISABLE?
Perhaps we can hook the kernel's handler for this bit?
/* 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.
4.48 KVM_DEASSIGN_PCI_DEVICE
@@ -1263,6 +1271,23 @@ struct kvm_assigned_msix_entry {
__u16 padding[3];
};
+5.54 KVM_ASSIGN_SET_INTX_MASK
4.54?
(54? wow.)
+
+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 if userspace lies?
+
+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.
+
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index fe83eb0..7f1627c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -468,6 +468,7 @@ 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;
@@ -477,6 +478,7 @@ 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];
};
I saw no reason this can't be a spinlock, but perhaps I missed
something. This would allow us to avoid srcu, which is slightly more
expensive than rcu. Since pci 2.3 assigned devices are not a major use
case, I'd like not to penalize the mainstream users for this.
This patch undoes some of the niceness of the previous patches, but I
have no alternative to suggest.
--
error compiling committee.c: too many arguments to function
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