mem: Remove redundant Packet::allocate calls

This patch cleans up the packet memory allocation confusion. The data
is always allocated at the requesting side, when a packet is created
(or copied), and there is never a need for any device to allocate any
space if it is merely responding to a paket. This behaviour is in line
with how SystemC and TLM works as well, thus increasing
interoperability, and matching established conventions.

The redundant calls to Packet::allocate are removed, and the checks in
the function are tightened up to make sure data is only ever allocated
once. There are still some oddities in the packet copy constructor
where we copy the data pointer if it is static (without ownership),
and allocate new space if the data is dynamic (with ownership). The
latter is being worked on further in a follow-on patch.

2 files changed, 0 insertions, 6 deletions

diff --git a/src/dev/virtio/base.cc b/src/dev/virtio/base.cc
index 44cce65c4..06c6e3452 100644
--- a/src/dev/virtio/base.cc
+++ b/src/dev/virtio/base.cc
@@ -422,7 +422,6 @@ void
 VirtIODeviceBase::readConfigBlob(PacketPtr pkt, Addr cfgOffset, const uint8_t *cfg)
 {
     const unsigned size(pkt->getSize());
-    pkt->allocate();
 
     if (cfgOffset + size > configSize)
         panic("Config read out of bounds.\n");
@@ -434,7 +433,6 @@ void
 VirtIODeviceBase::writeConfigBlob(PacketPtr pkt, Addr cfgOffset, uint8_t *cfg)
 {
     const unsigned size(pkt->getSize());
-    pkt->allocate();
 
     if (cfgOffset + size > configSize)
         panic("Config write out of bounds.\n");
diff --git a/src/dev/virtio/pci.cc b/src/dev/virtio/pci.cc
index 1f99d7fe4..c77b61934 100644
--- a/src/dev/virtio/pci.cc
+++ b/src/dev/virtio/pci.cc
@@ -75,8 +75,6 @@ PciVirtIO::read(PacketPtr pkt)
         return 0;
     }
 
-    pkt->allocate();
-
     switch(offset) {
       case OFF_DEVICE_FEATURES:
         DPRINTF(VIOPci, "   DEVICE_FEATURES request\n");
@@ -153,8 +151,6 @@ PciVirtIO::write(PacketPtr pkt)
         return 0;
     }
 
-    pkt->allocate();
-
     switch(offset) {
       case OFF_DEVICE_FEATURES:
         warn("Guest tried to write device features.");