hw/i386/kvm/xen_primary_console.c

   1 /*
   2  * QEMU Xen emulation: Primary console support
   3  *
   4  * Copyright © 2023 Amazon.com, Inc. or its affiliates. All Rights Reserved.
   5  *
   6  * Authors: David Woodhouse <dwmw2@infradead.org>
   7  *
   8  * This work is licensed under the terms of the GNU GPL, version 2 or later.
   9  * See the COPYING file in the top-level directory.
  10  */
  11
  12 #include "qemu/osdep.h"
  13
  14 #include "qapi/error.h"
  15
  16 #include "hw/sysbus.h"
  17 #include "hw/xen/xen.h"
  18 #include "hw/xen/xen_backend_ops.h"
  19 #include "xen_evtchn.h"
  20 #include "xen_overlay.h"
  21 #include "xen_primary_console.h"
  22
  23 #include "sysemu/kvm.h"
  24 #include "sysemu/kvm_xen.h"
  25
  26 #include "trace.h"
  27
  28 #include "hw/xen/interface/event_channel.h"
  29 #include "hw/xen/interface/grant_table.h"
  30
  31 #define TYPE_XEN_PRIMARY_CONSOLE "xen-primary-console"
  32 OBJECT_DECLARE_SIMPLE_TYPE(XenPrimaryConsoleState, XEN_PRIMARY_CONSOLE)
  33
  34 struct XenPrimaryConsoleState {
  35     /*< private >*/
  36     SysBusDevice busdev;
  37     /*< public >*/
  38
  39     MemoryRegion console_page;
  40     void *cp;
  41
  42     evtchn_port_t guest_port;
  43     evtchn_port_t be_port;
  44
  45     struct xengntdev_handle *gt;
  46     void *granted_xs;
  47 };
  48
  49 struct XenPrimaryConsoleState *xen_primary_console_singleton;
  50
  51 static void xen_primary_console_realize(DeviceState *dev, Error **errp)
  52 {
  53     XenPrimaryConsoleState *s = XEN_PRIMARY_CONSOLE(dev);
  54
  55     if (xen_mode != XEN_EMULATE) {
  56         error_setg(errp, "Xen primary console support is for Xen emulation");
  57         return;
  58     }
  59
  60     memory_region_init_ram(&s->console_page, OBJECT(dev), "xen:console_page",
  61                            XEN_PAGE_SIZE, &error_abort);
  62     memory_region_set_enabled(&s->console_page, true);
  63     s->cp = memory_region_get_ram_ptr(&s->console_page);
  64     memset(s->cp, 0, XEN_PAGE_SIZE);
  65
  66     /* We can't map it this early as KVM isn't ready */
  67     xen_primary_console_singleton = s;
  68 }
  69
  70 static void xen_primary_console_class_init(ObjectClass *klass, void *data)
  71 {
  72     DeviceClass *dc = DEVICE_CLASS(klass);
  73
  74     dc->realize = xen_primary_console_realize;
  75 }
  76
  77 static const TypeInfo xen_primary_console_info = {
  78     .name          = TYPE_XEN_PRIMARY_CONSOLE,
  79     .parent        = TYPE_SYS_BUS_DEVICE,
  80     .instance_size = sizeof(XenPrimaryConsoleState),
  81     .class_init    = xen_primary_console_class_init,
  82 };
  83
  84
  85 void xen_primary_console_create(void)
  86 {
  87     DeviceState *dev = sysbus_create_simple(TYPE_XEN_PRIMARY_CONSOLE, -1, NULL);
  88
  89     trace_xen_primary_console_create();
  90
  91     xen_primary_console_singleton = XEN_PRIMARY_CONSOLE(dev);
  92
  93     /*
  94      * Defer the init (xen_primary_console_reset()) until KVM is set up and the
  95      * overlay page can be mapped.
  96      */
  97 }
  98
  99 static void xen_primary_console_register_types(void)
 100 {
 101     type_register_static(&xen_primary_console_info);
 102 }
 103
 104 type_init(xen_primary_console_register_types)
 105
 106 uint16_t xen_primary_console_get_port(void)
 107 {
 108     XenPrimaryConsoleState *s = xen_primary_console_singleton;
 109     if (!s) {
 110         return 0;
 111     }
 112     return s->guest_port;
 113 }
 114
 115 void xen_primary_console_set_be_port(uint16_t port)
 116 {
 117     XenPrimaryConsoleState *s = xen_primary_console_singleton;
 118     if (s) {
 119         s->be_port = port;
 120     }
 121 }
 122
 123 uint64_t xen_primary_console_get_pfn(void)
 124 {
 125     XenPrimaryConsoleState *s = xen_primary_console_singleton;
 126     if (!s) {
 127         return 0;
 128     }
 129     return XEN_SPECIAL_PFN(CONSOLE);
 130 }
 131
 132 void *xen_primary_console_get_map(void)
 133 {
 134     XenPrimaryConsoleState *s = xen_primary_console_singleton;
 135     if (!s) {
 136         return 0;
 137     }
 138     return s->cp;
 139 }
 140
 141 static void alloc_guest_port(XenPrimaryConsoleState *s)
 142 {
 143     struct evtchn_alloc_unbound alloc = {
 144         .dom = DOMID_SELF,
 145         .remote_dom = DOMID_QEMU,
 146     };
 147
 148     if (!xen_evtchn_alloc_unbound_op(&alloc)) {
 149         s->guest_port = alloc.port;
 150     }
 151 }
 152
 153 static void rebind_guest_port(XenPrimaryConsoleState *s)
 154 {
 155     struct evtchn_bind_interdomain inter = {
 156         .remote_dom = DOMID_QEMU,
 157         .remote_port = s->be_port,
 158     };
 159
 160     if (!xen_evtchn_bind_interdomain_op(&inter)) {
 161         s->guest_port = inter.local_port;
 162     }
 163
 164     s->be_port = 0;
 165 }
 166
 167 int xen_primary_console_reset(void)
 168 {
 169     XenPrimaryConsoleState *s = xen_primary_console_singleton;
 170     if (!s) {
 171         return 0;
 172     }
 173
 174     if (!memory_region_is_mapped(&s->console_page)) {
 175         uint64_t gpa = XEN_SPECIAL_PFN(CONSOLE) << TARGET_PAGE_BITS;
 176         xen_overlay_do_map_page(&s->console_page, gpa);
 177     }
 178
 179     if (s->be_port) {
 180         rebind_guest_port(s);
 181     } else {
 182         alloc_guest_port(s);
 183     }
 184
 185     trace_xen_primary_console_reset(s->guest_port);
 186
 187     s->gt = qemu_xen_gnttab_open();
 188     uint32_t xs_gntref = GNTTAB_RESERVED_CONSOLE;
 189     s->granted_xs = qemu_xen_gnttab_map_refs(s->gt, 1, xen_domid, &xs_gntref,
 190                                              PROT_READ | PROT_WRITE);
 191
 192     return 0;
 193 }