qemu/hw/i386/kvm/xen_primary_console.h
David Woodhouse a72ccc7fc4 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>
2023-11-07 08:54:20 +00:00

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/*
* QEMU Xen emulation: Primary console support
*
* Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Authors: David Woodhouse <dwmw2@infradead.org>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#ifndef QEMU_XEN_PRIMARY_CONSOLE_H
#define QEMU_XEN_PRIMARY_CONSOLE_H
void xen_primary_console_create(void);
int xen_primary_console_reset(void);
uint16_t xen_primary_console_get_port(void);
void xen_primary_console_set_be_port(uint16_t port);
uint64_t xen_primary_console_get_pfn(void);
void *xen_primary_console_get_map(void);
#endif /* QEMU_XEN_PRIMARY_CONSOLE_H */