[PATCH 3/3] KVM: Add documents for MSI-X MMIO API

[Sheng Yang <sheng@linux.intel.com>]

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 Documentation/kvm/api.txt |   47 +++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 47 insertions(+), 0 deletions(-)

diff --git a/Documentation/kvm/api.txt b/Documentation/kvm/api.txt
index e1a9297..e6b7a1d 100644
--- a/Documentation/kvm/api.txt
+++ b/Documentation/kvm/api.txt
@@ -1263,6 +1263,53 @@ struct kvm_assigned_msix_entry {
 	__u16 padding[3];
 };
 
+4.54 KVM_REGISTER_MSIX_MMIO
+
+Capability: KVM_CAP_MSIX_MMIO
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_msix_mmio_user (in)
+Returns: 0 on success, -1 on error
+
+This API indicates an MSI-X MMIO address of a guest device. Then all MMIO
+operation would be handled by kernel. When necessary(e.g. MSI data/address
+changed), KVM would exit to userspace using KVM_EXIT_MSIX_ROUTING_UPDATE to
+indicate the MMIO modification and require userspace to update IRQ routing
+table.
+
+NOTICE: Writing the MSI-X MMIO page after it was registered with this API may
+be dangerous for userspace program. The writing during VM running may result
+in synchronization issue therefore the assigned device can't work properly.
+The writing is allowed when VM is not running and can be used as save/restore
+mechanism.
+
+struct kvm_msix_mmio_user {
+	__u32 dev_id;
+	__u16 type;		/* Device type and MMIO address type */
+	__u16 max_entries_nr;	/* Maximum entries supported */
+	__u64 base_addr;	/* Guest physical address of MMIO */
+	__u64 base_va;		/* Host virtual address of MMIO mapping */
+	__u64 flags;		/* Reserved for now */
+	__u64 reserved[4];
+};
+
+Current device type can be:
+#define KVM_MSIX_MMIO_TYPE_ASSIGNED_DEV	    (1 << 0)
+
+Current MMIO type can be:
+#define KVM_MSIX_MMIO_TYPE_BASE_TABLE	    (1 << 8)
+
+4.55 KVM_UNREGISTER_MSIX_MMIO
+
+Capability: KVM_CAP_MSIX_MMIO
+Architectures: x86
+Type: vm ioctl
+Parameters: struct kvm_msix_mmio_user (in)
+Returns: 0 on success, -1 on error
+
+This API would unregister the specific MSI-X MMIO, indicated by dev_id and
+type fields of struct kvm_msix_mmio_user.
+
 5. The kvm_run structure
 
 Application code obtains a pointer to the kvm_run structure by
-- 
1.7.0.1