tree dc8112aaca1611eb9bb733421be27f5947bfcb6d
parent 354ac20a36a82a5ee09b0a6c8ba8655358a7597f
author David Gibson <david@gibson.dropbear.id.au> 1317332352 +0000
committer Alexander Graf <agraf@suse.de> 1319991113 +0100

pseries: Use Book3S-HV TCE acceleration capabilities

The pseries machine of qemu implements the TCE mechanism used as a
virtual IOMMU for the PAPR defined virtual IO devices.  Because the
PAPR spec only defines a small DMA address space, the guest VIO
drivers need to update TCE mappings very frequently - the virtual
network device is particularly bad.  This means many slow exits to
qemu to emulate the H_PUT_TCE hypercall.

Sufficiently recent kernels allow this to be mitigated by implementing
H_PUT_TCE in the host kernel.  To make use of this, however, qemu
needs to initialize the necessary TCE tables, and map them into itself
so that the VIO device implementations can retrieve the mappings when
they access guest memory (which is treated as a virtual DMA
operation).

This patch adds the necessary calls to use the KVM TCE acceleration.
If the kernel does not support acceleration, or there is some other
error creating the accelerated TCE table, then it will still fall back
to full userspace TCE implementation.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>