Lguest support for Virtio

This makes lguest able to use the virtio devices.

We change the device descriptor page from a simple array to a variable
length "type, config_len, status, config data..." format, and
implement virtio_config_ops to read from that config data.

We use the virtio ring implementation for an efficient Guest <-> Host
virtqueue mechanism, and the new LHCALL_NOTIFY hypercall to kick the
host when it changes.

We also use LHCALL_NOTIFY on kernel addresses for very very early
console output.  We could have another hypercall, but this hack works
quite well.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/x86/lguest/Kconfig b/arch/x86/lguest/Kconfig
index 44dccfd845f8..c4dffbeea5e1 100644
--- a/arch/x86/lguest/Kconfig
+++ b/arch/x86/lguest/Kconfig
@@ -2,8 +2,13 @@ config LGUEST_GUEST
         bool "Lguest guest support"
         select PARAVIRT
         depends on !X86_PAE
+        select VIRTIO
         select VIRTIO_RING
+        select VIRTIO_CONSOLE
         help
           Lguest is a tiny in-kernel hypervisor.  Selecting this will
           allow your kernel to boot under lguest.  This option will increase
           your kernel size by about 6k.  If in doubt, say N.
+
+          If you say Y here, make sure you say Y (or M) to the virtio block
+          and net drivers which lguest needs.