crosvm: add virtio MMIO transport module

The MMIO transport, along with PCI, is a standard transport for
discovering and configuring virtio devices and their associated queues.
MMIO is by far easier and simpler and so gets implemented first.

BUG=None
TEST=None

Change-Id: Icdaa02284aedf8ec726199784da45d22c8dbab87
Reviewed-on: https://chromium-review.googlesource.com/514687
Commit-Ready: Zach Reizner <zachr@chromium.org>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/src/hw/virtio/mod.rs b/src/hw/virtio/mod.rs
index 51af2b3..cfb22e3 100644
--- a/src/hw/virtio/mod.rs
+++ b/src/hw/virtio/mod.rs
@@ -5,5 +5,21 @@
 //! Implements virtio devices, queues, and transport mechanisms.
 
 mod queue;
+mod mmio;
 
 pub use self::queue::*;
+pub use self::mmio::*;
+
+const DEVICE_ACKNOWLEDGE: u32 = 0x01;
+const DEVICE_DRIVER: u32 = 0x02;
+const DEVICE_DRIVER_OK: u32 = 0x04;
+const DEVICE_FEATURES_OK: u32 = 0x08;
+const DEVICE_FAILED: u32 = 0x80;
+
+const TYPE_BLOCK: u32 = 2;
+
+const INTERRUPT_STATUS_USED_RING: u32 = 0x1;
+
+/// Offset from the base MMIO address of a virtio device used by the guest to notify the device of
+/// queue events.
+pub const NOITFY_REG_OFFSET: u32 = 0x50;