On 09/11/17 14:16, Brijesh Singh wrote: > 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 >
Reviewed-by: Laszlo Ersek <ler...@redhat.com> _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
