In next patches we will update Virtio transmit to use the device-mapped address of the caller-supplied packet. The patch documents the new model.
Cc: Ard Biesheuvel <ard.biesheu...@linaro.org> Cc: Jordan Justen <jordan.l.jus...@intel.com> Cc: Tom Lendacky <thomas.lenda...@amd.com> Cc: Laszlo Ersek <ler...@redhat.com> Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Brijesh Singh <brijesh.si...@amd.com> --- OvmfPkg/VirtioNetDxe/TechNotes.txt | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) diff --git a/OvmfPkg/VirtioNetDxe/TechNotes.txt b/OvmfPkg/VirtioNetDxe/TechNotes.txt index f39426fb13e4..c6ca341ead15 100644 --- a/OvmfPkg/VirtioNetDxe/TechNotes.txt +++ b/OvmfPkg/VirtioNetDxe/TechNotes.txt @@ -312,10 +312,14 @@ in the following: that is shared by all of the head descriptors. This virtio-net request header is never modified by the host. -- Each tail descriptor is re-pointed to the caller-supplied packet buffer - whenever VirtioNetTransmit places the corresponding head descriptor on the - Available Ring. The caller is responsible to hang on to the unmodified buffer - until it is reported transmitted by VirtioNetGetStatus. +- Each tail descriptor is re-pointed to the device-mapped address of the + caller-supplied packet buffer whenever VirtioNetTransmit places the + corresponding head descriptor on the Available Ring. A reverse mapping, from + the device-mapped address to the caller-supplied packet address, is saved in + an associative data structure that belongs to the driver instance. + +- Per spec, the caller is responsible to hang on to the unmodified packet + buffer until it is reported transmitted by VirtioNetGetStatus. Steps of packet transmission: @@ -338,9 +342,11 @@ Steps of packet transmission: - Client code calls VirtioNetGetStatus. In case the Used Ring is empty, the function reports no Tx completion. Otherwise, a head descriptor's index is consumed from the Used Ring and recycled to the private stack. The client - code's original packet buffer address is fetched from the tail descriptor - (where it has been stored at VirtioNetTransmit time) and returned to the - caller. + code's original packet buffer address is calculated by fetching the + device-mapped address from the tail descriptor (where it has been stored at + VirtioNetTransmit time), and by looking up the device-mapped address in the + associative data structure. The reverse-mapped packet buffer address is + returned to the caller. - The Len field of the Used Ring Element is not checked. The host is assumed to have transmitted the entire packet -- VirtioNetTransmit had forced it below -- 2.9.4 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
