hw/xen: add support for Xen primary console in emulated mode

The primary console is special because the toolstack maps a page into
the guest for its ring, and also allocates the guest-side event channel.
The guest's grant table is even primed to export that page using a known
grant ref#. Add support for all that in emulated mode, so that we can
have a primary console.

For reasons unclear, the backends running under real Xen don't just use
a mapping of the well-known GNTTAB_RESERVED_CONSOLE grant ref (which
would also be in the ring-ref node in XenStore). Instead, the toolstack
sets the ring-ref node of the primary console to the GFN of the guest
page. The backend is expected to handle that special case and map it
with foreignmem operations instead.

We don't have an implementation of foreignmem ops for emulated Xen mode,
so just make it map GNTTAB_RESERVED_CONSOLE instead. This would probably
work for real Xen too, but we can't work out how to make real Xen create
a primary console of type "ioemu" to make QEMU drive it, so we can't
test that; might as well leave it as it is for now under Xen.

Now at last we can boot the Xen PV shim and run PV kernels in QEMU.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/hw/i386/kvm/xen-stubs.c b/hw/i386/kvm/xen-stubs.c
index ae406e0b02..d03131e686 100644
--- a/hw/i386/kvm/xen-stubs.c
+++ b/hw/i386/kvm/xen-stubs.c
@@ -15,6 +15,7 @@
 #include "qapi/qapi-commands-misc-target.h"
 
 #include "xen_evtchn.h"
+#include "xen_primary_console.h"
 
 void xen_evtchn_snoop_msi(PCIDevice *dev, bool is_msix, unsigned int vector,
                           uint64_t addr, uint32_t data, bool is_masked)
@@ -30,6 +31,13 @@ bool xen_evtchn_deliver_pirq_msi(uint64_t address, uint32_t data)
     return false;
 }
 
+void xen_primary_console_create(void)
+{
+}
+
+void xen_primary_console_set_be_port(uint16_t port)
+{
+}
 #ifdef TARGET_I386
 EvtchnInfoList *qmp_xen_event_list(Error **errp)
 {