BaseTools/CommonLib: drop the use of MAX_ADDRESS

[mirror_edk2.git] / OvmfPkg / VirtioNetDxe / TechNotes.txt

diff --git a/OvmfPkg/VirtioNetDxe/TechNotes.txt b/OvmfPkg/VirtioNetDxe/TechNotes.txt
index 86b91f5614950f83b3e13c1462a269b9ea8fe1bc..cd38750a4afb060e957d1126f4cb0ec09814fc18 100644 (file)
--- a/OvmfPkg/VirtioNetDxe/TechNotes.txt
+++ b/OvmfPkg/VirtioNetDxe/TechNotes.txt
@@ -69,9 +69,14 @@ faithfully indented) that implement the transition.
   [SnpInitialize.c]            |  | [SnpShutdown.c]\r
   VirtioNetInitialize          |  | VirtioNetShutdown\r
     VirtioNetInitRing {Rx, Tx} |  |   VirtioNetShutdownRx [SnpSharedHelpers.c]\r
-      VirtioRingInit           |  |   VirtioNetShutdownTx [SnpSharedHelpers.c]\r
-    VirtioNetInitTx            |  |   VirtioNetUninitRing [SnpSharedHelpers.c]\r
-    VirtioNetInitRx            |  |                       {Tx, Rx}\r
+      VirtioRingInit           |  |     VirtIo->UnmapSharedBuffer\r
+      VirtioRingMap            |  |     VirtIo->FreeSharedPages\r
+    VirtioNetInitTx            |  |   VirtioNetShutdownTx [SnpSharedHelpers.c]\r
+      VirtIo->AllocateShare... |  |     VirtIo->UnmapSharedBuffer\r
+      VirtioMapAllBytesInSh... |  |     VirtIo->FreeSharedPages\r
+    VirtioNetInitRx            |  |   VirtioNetUninitRing [SnpSharedHelpers.c]\r
+      VirtIo->AllocateShare... |  |                       {Tx, Rx}\r
+      VirtioMapAllBytesInSh... |  |     VirtIo->UnmapSharedBuffer\r
                                |  |     VirtioRingUninit\r
                                v  |\r
                   +-----------------------------+\r
@@ -246,7 +251,7 @@ In VirtioNetInitRx, the guest allocates the fixed size Receive Destination
 Area, which accommodates all packets delivered asynchronously by the host. To\r
 each packet, a slice of this area is dedicated; each slice is further\r
 subdivided into virtio-net request header and network packet data. The\r
-(guest-physical) addresses of these sub-slices are denoted with A2, A3, A4 and\r
+(device-physical) addresses of these sub-slices are denoted with A2, A3, A4 and\r
 so on. Importantly, an even-subscript "A" always belongs to a virtio-net\r
 request header, while an odd-subscript "A" always belongs to a packet\r
 sub-slice.\r
@@ -311,10 +316,14 @@ in the following:
   that is shared by all of the head descriptors. This virtio-net request header\r
   is never modified by the host.\r
 \r
-- Each tail descriptor is re-pointed to the caller-supplied packet buffer\r
-  whenever VirtioNetTransmit places the corresponding head descriptor on the\r
-  Available Ring. The caller is responsible to hang on to the unmodified buffer\r
-  until it is reported transmitted by VirtioNetGetStatus.\r
+- Each tail descriptor is re-pointed to the device-mapped address of the\r
+  caller-supplied packet buffer whenever VirtioNetTransmit places the\r
+  corresponding head descriptor on the Available Ring. A reverse mapping, from\r
+  the device-mapped address to the caller-supplied packet address, is saved in\r
+  an associative data structure that belongs to the driver instance.\r
+\r
+- Per spec, the caller is responsible to hang on to the unmodified packet\r
+  buffer until it is reported transmitted by VirtioNetGetStatus.\r
 \r
 Steps of packet transmission:\r
 \r
@@ -337,9 +346,11 @@ Steps of packet transmission:
 - Client code calls VirtioNetGetStatus. In case the Used Ring is empty, the\r
   function reports no Tx completion. Otherwise, a head descriptor's index is\r
   consumed from the Used Ring and recycled to the private stack. The client\r
-  code's original packet buffer address is fetched from the tail descriptor\r
-  (where it has been stored at VirtioNetTransmit time) and returned to the\r
-  caller.\r
+  code's original packet buffer address is calculated by fetching the\r
+  device-mapped address from the tail descriptor (where it has been stored at\r
+  VirtioNetTransmit time), and by looking up the device-mapped address in the\r
+  associative data structure. The reverse-mapped packet buffer address is\r
+  returned to the caller.\r
 \r
 - The Len field of the Used Ring Element is not checked. The host is assumed to\r
   have transmitted the entire packet -- VirtioNetTransmit had forced it below\r