include/hw/xen/xen_backend_ops.h

/*
 * QEMU Xen backend support
 *
 * Copyright © 2022 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_BACKEND_OPS_H
#define QEMU_XEN_BACKEND_OPS_H

/*
 * For the time being, these operations map fairly closely to the API of
 * the actual Xen libraries, e.g. libxenevtchn. As we complete the migration
 * from XenLegacyDevice back ends to the new XenDevice model, they may
 * evolve to slightly higher-level APIs.
 *
 * The internal emulations do not emulate the Xen APIs entirely faithfully;
 * only enough to be used by the Xen backend devices. For example, only one
 * event channel can be bound to each handle, since that's sufficient for
 * the device support (only the true Xen HVM backend uses more). And the
 * behaviour of unmask() and pending() is different too because the device
 * backends don't care.
 */

typedef struct xenevtchn_handle xenevtchn_handle;
typedef int xenevtchn_port_or_error_t;
typedef uint32_t evtchn_port_t;
typedef uint16_t domid_t;
typedef uint32_t grant_ref_t;

#define XEN_PAGE_SHIFT       12
#define XEN_PAGE_SIZE        (1UL << XEN_PAGE_SHIFT)
#define XEN_PAGE_MASK        (~(XEN_PAGE_SIZE - 1))

struct evtchn_backend_ops {
    xenevtchn_handle *(*open)(void);
    int (*bind_interdomain)(xenevtchn_handle *xc, uint32_t domid,
                            evtchn_port_t guest_port);
    int (*unbind)(xenevtchn_handle *xc, evtchn_port_t port);
    int (*close)(struct xenevtchn_handle *xc);
    int (*get_fd)(struct xenevtchn_handle *xc);
    int (*notify)(struct xenevtchn_handle *xc, evtchn_port_t port);
    int (*unmask)(struct xenevtchn_handle *xc, evtchn_port_t port);
    int (*pending)(struct xenevtchn_handle *xc);
};

extern struct evtchn_backend_ops *xen_evtchn_ops;

static inline xenevtchn_handle *qemu_xen_evtchn_open(void)
{
    if (!xen_evtchn_ops) {
        return NULL;
    }
    return xen_evtchn_ops->open();
}

static inline int qemu_xen_evtchn_bind_interdomain(xenevtchn_handle *xc,
                                                   uint32_t domid,
                                                   evtchn_port_t guest_port)
{
    if (!xen_evtchn_ops) {
        return -ENOSYS;
    }
    return xen_evtchn_ops->bind_interdomain(xc, domid, guest_port);
}

static inline int qemu_xen_evtchn_unbind(xenevtchn_handle *xc,
                                         evtchn_port_t port)
{
    if (!xen_evtchn_ops) {
        return -ENOSYS;
    }
    return xen_evtchn_ops->unbind(xc, port);
}

static inline int qemu_xen_evtchn_close(xenevtchn_handle *xc)
{
    if (!xen_evtchn_ops) {
        return -ENOSYS;
    }
    return xen_evtchn_ops->close(xc);
}

static inline int qemu_xen_evtchn_fd(xenevtchn_handle *xc)
{
    if (!xen_evtchn_ops) {
        return -ENOSYS;
    }
    return xen_evtchn_ops->get_fd(xc);
}

static inline int qemu_xen_evtchn_notify(xenevtchn_handle *xc,
                                         evtchn_port_t port)
{
    if (!xen_evtchn_ops) {
        return -ENOSYS;
    }
    return xen_evtchn_ops->notify(xc, port);
}

static inline int qemu_xen_evtchn_unmask(xenevtchn_handle *xc,
                                         evtchn_port_t port)
{
    if (!xen_evtchn_ops) {
        return -ENOSYS;
    }
    return xen_evtchn_ops->unmask(xc, port);
}

static inline int qemu_xen_evtchn_pending(xenevtchn_handle *xc)
{
    if (!xen_evtchn_ops) {
        return -ENOSYS;
    }
    return xen_evtchn_ops->pending(xc);
}

typedef struct xengntdev_handle xengnttab_handle;

typedef struct XenGrantCopySegment {
    union {
        void *virt;
        struct {
            uint32_t ref;
            off_t offset;
        } foreign;
    } source, dest;
    size_t len;
} XenGrantCopySegment;

#define XEN_GNTTAB_OP_FEATURE_MAP_MULTIPLE  (1U << 0)

struct gnttab_backend_ops {
    uint32_t features;
    xengnttab_handle *(*open)(void);
    int (*close)(xengnttab_handle *xgt);
    int (*grant_copy)(xengnttab_handle *xgt, bool to_domain, uint32_t domid,
                      XenGrantCopySegment *segs, uint32_t nr_segs,
                      Error **errp);
    int (*set_max_grants)(xengnttab_handle *xgt, uint32_t nr_grants);
    void *(*map_refs)(xengnttab_handle *xgt, uint32_t count, uint32_t domid,
                      uint32_t *refs, int prot);
    int (*unmap)(xengnttab_handle *xgt, void *start_address, uint32_t count);
};

extern struct gnttab_backend_ops *xen_gnttab_ops;

static inline bool qemu_xen_gnttab_can_map_multi(void)
{
    return xen_gnttab_ops &&
        !!(xen_gnttab_ops->features & XEN_GNTTAB_OP_FEATURE_MAP_MULTIPLE);
}

static inline xengnttab_handle *qemu_xen_gnttab_open(void)
{
    if (!xen_gnttab_ops) {
        return NULL;
    }
    return xen_gnttab_ops->open();
}

static inline int qemu_xen_gnttab_close(xengnttab_handle *xgt)
{
    if (!xen_gnttab_ops) {
        return -ENOSYS;
    }
    return xen_gnttab_ops->close(xgt);
}

static inline int qemu_xen_gnttab_grant_copy(xengnttab_handle *xgt,
                                             bool to_domain, uint32_t domid,
                                             XenGrantCopySegment *segs,
                                             uint32_t nr_segs, Error **errp)
{
    if (!xen_gnttab_ops) {
        return -ENOSYS;
    }

    return xen_gnttab_ops->grant_copy(xgt, to_domain, domid, segs, nr_segs,
                                      errp);
}

static inline int qemu_xen_gnttab_set_max_grants(xengnttab_handle *xgt,
                                                 uint32_t nr_grants)
{
    if (!xen_gnttab_ops) {
        return -ENOSYS;
    }
    return xen_gnttab_ops->set_max_grants(xgt, nr_grants);
}

static inline void *qemu_xen_gnttab_map_refs(xengnttab_handle *xgt,
                                             uint32_t count, uint32_t domid,
                                             uint32_t *refs, int prot)
{
    if (!xen_gnttab_ops) {
        return NULL;
    }
    return xen_gnttab_ops->map_refs(xgt, count, domid, refs, prot);
}

static inline int qemu_xen_gnttab_unmap(xengnttab_handle *xgt,
                                        void *start_address,
                                        uint32_t count)
{
    if (!xen_gnttab_ops) {
        return -ENOSYS;
    }
    return xen_gnttab_ops->unmap(xgt, start_address, count);
}

void setup_xen_backend_ops(void);

#endif /* QEMU_XEN_BACKEND_OPS_H */