Merge branch 'xenfv-kvm-15' of git://git.infradead.org/users/dwmw2/qemu into HEAD

This adds support for emulating Xen under Linux/KVM, based on kernel
patches which have been present since Linux v5.12. As with the kernel
support, it's derived from work started by João Martins of Oracle in
2018.

This series just adds the basic platform support — CPUID, hypercalls,
event channels, a stub of XenStore.

A full single-tenant internal implementation of XenStore, and patches
to make QEMU's Xen PV drivers work with this Xen emulation, are waiting
in the wings to be submitted in a follow-on patch series.

As noted in the documentation, it's enabled by setting the xen-version
property on the KVM accelerator, e.g.:

 qemu-system-x86_64 -serial mon:stdio -M q35 -display none -m 1G -smp 2 \
    -accel kvm,xen-version=0x4000e,kernel-irqchip=split \
    -kernel vmlinuz-6.0.7-301.fc37.x86_64 \
    -append "console=ttyS0 root=/dev/sda1" \
    -drive file=/var/lib/libvirt/images/fedora28.qcow2,if=none,id=disk \
    -device ahci,id=ahci -device ide-hd,drive=disk,bus=ahci.0

Even before this was merged, we've already been using it to find and fix
bugs in the Linux kernel Xen guest support:

https://lore.kernel.org/all/4bffa69a949bfdc92c4a18e5a1c3cbb3b94a0d32.camel@infradead.org/
https://lore.kernel.org/all/871qnunycr.ffs@tglx/

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 232 insertions, 0 deletions

diff --git a/hw/i386/kvm/xen_gnttab.c b/hw/i386/kvm/xen_gnttab.c
new file mode 100644
index 0000000000..1e691ded32
--- /dev/null
+++ b/hw/i386/kvm/xen_gnttab.c
@@ -0,0 +1,232 @@
+/*
+ * QEMU Xen emulation: Grant table 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.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/host-utils.h"
+#include "qemu/module.h"
+#include "qemu/lockable.h"
+#include "qemu/main-loop.h"
+#include "qapi/error.h"
+#include "qom/object.h"
+#include "exec/target_page.h"
+#include "exec/address-spaces.h"
+#include "migration/vmstate.h"
+
+#include "hw/sysbus.h"
+#include "hw/xen/xen.h"
+#include "xen_overlay.h"
+#include "xen_gnttab.h"
+
+#include "sysemu/kvm.h"
+#include "sysemu/kvm_xen.h"
+
+#include "hw/xen/interface/memory.h"
+#include "hw/xen/interface/grant_table.h"
+
+#define TYPE_XEN_GNTTAB "xen-gnttab"
+OBJECT_DECLARE_SIMPLE_TYPE(XenGnttabState, XEN_GNTTAB)
+
+#define XEN_PAGE_SHIFT 12
+#define XEN_PAGE_SIZE (1ULL << XEN_PAGE_SHIFT)
+
+#define ENTRIES_PER_FRAME_V1 (XEN_PAGE_SIZE / sizeof(grant_entry_v1_t))
+
+struct XenGnttabState {
+    /*< private >*/
+    SysBusDevice busdev;
+    /*< public >*/
+
+    QemuMutex gnt_lock;
+
+    uint32_t nr_frames;
+    uint32_t max_frames;
+
+    union {
+        grant_entry_v1_t *v1;
+        /* Theoretically, v2 support could be added here. */
+    } entries;
+
+    MemoryRegion gnt_frames;
+    MemoryRegion *gnt_aliases;
+    uint64_t *gnt_frame_gpas;
+};
+
+struct XenGnttabState *xen_gnttab_singleton;
+
+static void xen_gnttab_realize(DeviceState *dev, Error **errp)
+{
+    XenGnttabState *s = XEN_GNTTAB(dev);
+    int i;
+
+    if (xen_mode != XEN_EMULATE) {
+        error_setg(errp, "Xen grant table support is for Xen emulation");
+        return;
+    }
+    s->nr_frames = 0;
+    s->max_frames = kvm_xen_get_gnttab_max_frames();
+    memory_region_init_ram(&s->gnt_frames, OBJECT(dev), "xen:grant_table",
+                           XEN_PAGE_SIZE * s->max_frames, &error_abort);
+    memory_region_set_enabled(&s->gnt_frames, true);
+    s->entries.v1 = memory_region_get_ram_ptr(&s->gnt_frames);
+    memset(s->entries.v1, 0, XEN_PAGE_SIZE * s->max_frames);
+
+    /* Create individual page-sizes aliases for overlays */
+    s->gnt_aliases = (void *)g_new0(MemoryRegion, s->max_frames);
+    s->gnt_frame_gpas = (void *)g_new(uint64_t, s->max_frames);
+    for (i = 0; i < s->max_frames; i++) {
+        memory_region_init_alias(&s->gnt_aliases[i], OBJECT(dev),
+                                 NULL, &s->gnt_frames,
+                                 i * XEN_PAGE_SIZE, XEN_PAGE_SIZE);
+        s->gnt_frame_gpas[i] = INVALID_GPA;
+    }
+
+    qemu_mutex_init(&s->gnt_lock);
+
+    xen_gnttab_singleton = s;
+}
+
+static int xen_gnttab_post_load(void *opaque, int version_id)
+{
+    XenGnttabState *s = XEN_GNTTAB(opaque);
+    uint32_t i;
+
+    for (i = 0; i < s->nr_frames; i++) {
+        if (s->gnt_frame_gpas[i] != INVALID_GPA) {
+            xen_overlay_do_map_page(&s->gnt_aliases[i], s->gnt_frame_gpas[i]);
+        }
+    }
+    return 0;
+}
+
+static bool xen_gnttab_is_needed(void *opaque)
+{
+    return xen_mode == XEN_EMULATE;
+}
+
+static const VMStateDescription xen_gnttab_vmstate = {
+    .name = "xen_gnttab",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = xen_gnttab_is_needed,
+    .post_load = xen_gnttab_post_load,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT32(nr_frames, XenGnttabState),
+        VMSTATE_VARRAY_UINT32(gnt_frame_gpas, XenGnttabState, nr_frames, 0,
+                              vmstate_info_uint64, uint64_t),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void xen_gnttab_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->realize = xen_gnttab_realize;
+    dc->vmsd = &xen_gnttab_vmstate;
+}
+
+static const TypeInfo xen_gnttab_info = {
+    .name          = TYPE_XEN_GNTTAB,
+    .parent        = TYPE_SYS_BUS_DEVICE,
+    .instance_size = sizeof(XenGnttabState),
+    .class_init    = xen_gnttab_class_init,
+};
+
+void xen_gnttab_create(void)
+{
+    xen_gnttab_singleton = XEN_GNTTAB(sysbus_create_simple(TYPE_XEN_GNTTAB,
+                                                           -1, NULL));
+}
+
+static void xen_gnttab_register_types(void)
+{
+    type_register_static(&xen_gnttab_info);
+}
+
+type_init(xen_gnttab_register_types)
+
+int xen_gnttab_map_page(uint64_t idx, uint64_t gfn)
+{
+    XenGnttabState *s = xen_gnttab_singleton;
+    uint64_t gpa = gfn << XEN_PAGE_SHIFT;
+
+    if (!s) {
+        return -ENOTSUP;
+    }
+
+    if (idx >= s->max_frames) {
+        return -EINVAL;
+    }
+
+    QEMU_IOTHREAD_LOCK_GUARD();
+    QEMU_LOCK_GUARD(&s->gnt_lock);
+
+    xen_overlay_do_map_page(&s->gnt_aliases[idx], gpa);
+
+    s->gnt_frame_gpas[idx] = gpa;
+
+    if (s->nr_frames <= idx) {
+        s->nr_frames = idx + 1;
+    }
+
+    return 0;
+}
+
+int xen_gnttab_set_version_op(struct gnttab_set_version *set)
+{
+    int ret;
+
+    switch (set->version) {
+    case 1:
+        ret = 0;
+        break;
+
+    case 2:
+        /* Behave as before set_version was introduced. */
+        ret = -ENOSYS;
+        break;
+
+    default:
+        ret = -EINVAL;
+    }
+
+    set->version = 1;
+    return ret;
+}
+
+int xen_gnttab_get_version_op(struct gnttab_get_version *get)
+{
+    if (get->dom != DOMID_SELF && get->dom != xen_domid) {
+        return -ESRCH;
+    }
+
+    get->version = 1;
+    return 0;
+}
+
+int xen_gnttab_query_size_op(struct gnttab_query_size *size)
+{
+    XenGnttabState *s = xen_gnttab_singleton;
+
+    if (!s) {
+        return -ENOTSUP;
+    }
+
+    if (size->dom != DOMID_SELF && size->dom != xen_domid) {
+        size->status = GNTST_bad_domain;
+        return 0;
+    }
+
+    size->status = GNTST_okay;
+    size->nr_frames = s->nr_frames;
+    size->max_nr_frames = s->max_frames;
+    return 0;
+}