hw/remote/mpqemu-link.c

   1 /*
   2  * Communication channel between QEMU and remote device process
   3  *
   4  * Copyright © 2018, 2021 Oracle and/or its affiliates.
   5  *
   6  * This work is licensed under the terms of the GNU GPL, version 2 or later.
   7  * See the COPYING file in the top-level directory.
   8  *
   9  */
  10
  11 #include "qemu/osdep.h"
  12
  13 #include "qemu/module.h"
  14 #include "hw/remote/mpqemu-link.h"
  15 #include "qapi/error.h"
  16 #include "qemu/iov.h"
  17 #include "qemu/error-report.h"
  18 #include "qemu/main-loop.h"
  19 #include "io/channel.h"
  20 #include "sysemu/iothread.h"
  21 #include "trace.h"
  22
  23 /*
  24  * Send message over the ioc QIOChannel.
  25  * This function is safe to call from:
  26  * - main loop in co-routine context. Will block the main loop if not in
  27  *   co-routine context;
  28  * - vCPU thread with no co-routine context and if the channel is not part
  29  *   of the main loop handling;
  30  * - IOThread within co-routine context, outside of co-routine context
  31  *   will block IOThread;
  32  * Returns true if no errors were encountered, false otherwise.
  33  */
  34 bool mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
  35 {
  36     bool drop_bql = bql_locked();
  37     bool iothread = qemu_in_iothread();
  38     struct iovec send[2] = {};
  39     int *fds = NULL;
  40     size_t nfds = 0;
  41     bool ret = false;
  42
  43     send[0].iov_base = msg;
  44     send[0].iov_len = MPQEMU_MSG_HDR_SIZE;
  45
  46     send[1].iov_base = (void *)&msg->data;
  47     send[1].iov_len = msg->size;
  48
  49     if (msg->num_fds) {
  50         nfds = msg->num_fds;
  51         fds = msg->fds;
  52     }
  53
  54     /*
  55      * Dont use in IOThread out of co-routine context as
  56      * it will block IOThread.
  57      */
  58     assert(qemu_in_coroutine() || !iothread);
  59
  60     /*
  61      * Skip unlocking/locking BQL when the IOThread is running
  62      * in co-routine context. Co-routine context is asserted above
  63      * for IOThread case.
  64      * Also skip lock handling while in a co-routine in the main context.
  65      */
  66     if (drop_bql && !iothread && !qemu_in_coroutine()) {
  67         bql_unlock();
  68     }
  69
  70     if (!qio_channel_writev_full_all(ioc, send, G_N_ELEMENTS(send),
  71                                     fds, nfds, 0, errp)) {
  72         ret = true;
  73     } else {
  74         trace_mpqemu_send_io_error(msg->cmd, msg->size, nfds);
  75     }
  76
  77     if (drop_bql && !iothread && !qemu_in_coroutine()) {
  78         /* See above comment why skip locking here. */
  79         bql_lock();
  80     }
  81
  82     return ret;
  83 }
  84
  85 /*
  86  * Read message from the ioc QIOChannel.
  87  * This function is safe to call from:
  88  * - From main loop in co-routine context. Will block the main loop if not in
  89  *   co-routine context;
  90  * - From vCPU thread with no co-routine context and if the channel is not part
  91  *   of the main loop handling;
  92  * - From IOThread within co-routine context, outside of co-routine context
  93  *   will block IOThread;
  94  */
  95 static ssize_t mpqemu_read(QIOChannel *ioc, void *buf, size_t len, int **fds,
  96                            size_t *nfds, Error **errp)
  97 {
  98     struct iovec iov = { .iov_base = buf, .iov_len = len };
  99     bool drop_bql = bql_locked();
 100     bool iothread = qemu_in_iothread();
 101     int ret = -1;
 102
 103     /*
 104      * Dont use in IOThread out of co-routine context as
 105      * it will block IOThread.
 106      */
 107     assert(qemu_in_coroutine() || !iothread);
 108
 109     if (drop_bql && !iothread && !qemu_in_coroutine()) {
 110         bql_unlock();
 111     }
 112
 113     ret = qio_channel_readv_full_all_eof(ioc, &iov, 1, fds, nfds, errp);
 114
 115     if (drop_bql && !iothread && !qemu_in_coroutine()) {
 116         bql_lock();
 117     }
 118
 119     return (ret <= 0) ? ret : iov.iov_len;
 120 }
 121
 122 bool mpqemu_msg_recv(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
 123 {
 124     ERRP_GUARD();
 125     g_autofree int *fds = NULL;
 126     size_t nfds = 0;
 127     ssize_t len;
 128     bool ret = false;
 129
 130     len = mpqemu_read(ioc, msg, MPQEMU_MSG_HDR_SIZE, &fds, &nfds, errp);
 131     if (len <= 0) {
 132         goto fail;
 133     } else if (len != MPQEMU_MSG_HDR_SIZE) {
 134         error_setg(errp, "Message header corrupted");
 135         goto fail;
 136     }
 137
 138     if (msg->size > sizeof(msg->data)) {
 139         error_setg(errp, "Invalid size for message");
 140         goto fail;
 141     }
 142
 143     if (!msg->size) {
 144         goto copy_fds;
 145     }
 146
 147     len = mpqemu_read(ioc, &msg->data, msg->size, NULL, NULL, errp);
 148     if (len <= 0) {
 149         goto fail;
 150     }
 151     if (len != msg->size) {
 152         error_setg(errp, "Unable to read full message");
 153         goto fail;
 154     }
 155
 156 copy_fds:
 157     msg->num_fds = nfds;
 158     if (nfds > G_N_ELEMENTS(msg->fds)) {
 159         error_setg(errp,
 160                    "Overflow error: received %zu fds, more than max of %d fds",
 161                    nfds, REMOTE_MAX_FDS);
 162         goto fail;
 163     }
 164     if (nfds) {
 165         memcpy(msg->fds, fds, nfds * sizeof(int));
 166     }
 167
 168     ret = true;
 169
 170 fail:
 171     if (*errp) {
 172         trace_mpqemu_recv_io_error(msg->cmd, msg->size, nfds);
 173     }
 174     while (*errp && nfds) {
 175         close(fds[nfds - 1]);
 176         nfds--;
 177     }
 178
 179     return ret;
 180 }
 181
 182 /*
 183  * Send msg and wait for a reply with command code RET_MSG.
 184  * Returns the message received of size u64 or UINT64_MAX
 185  * on error.
 186  * Called from VCPU thread in non-coroutine context.
 187  * Used by the Proxy object to communicate to remote processes.
 188  */
 189 uint64_t mpqemu_msg_send_and_await_reply(MPQemuMsg *msg, PCIProxyDev *pdev,
 190                                          Error **errp)
 191 {
 192     MPQemuMsg msg_reply = {0};
 193     uint64_t ret = UINT64_MAX;
 194
 195     assert(!qemu_in_coroutine());
 196
 197     QEMU_LOCK_GUARD(&pdev->io_mutex);
 198     if (!mpqemu_msg_send(msg, pdev->ioc, errp)) {
 199         return ret;
 200     }
 201
 202     if (!mpqemu_msg_recv(&msg_reply, pdev->ioc, errp)) {
 203         return ret;
 204     }
 205
 206     if (!mpqemu_msg_valid(&msg_reply) || msg_reply.cmd != MPQEMU_CMD_RET) {
 207         error_setg(errp, "ERROR: Invalid reply received for command %d",
 208                          msg->cmd);
 209         return ret;
 210     }
 211
 212     return msg_reply.data.u64;
 213 }
 214
 215 bool mpqemu_msg_valid(MPQemuMsg *msg)
 216 {
 217     if (msg->cmd >= MPQEMU_CMD_MAX || msg->cmd < 0) {
 218         return false;
 219     }
 220
 221     /* Verify FDs. */
 222     if (msg->num_fds >= REMOTE_MAX_FDS) {
 223         return false;
 224     }
 225
 226     if (msg->num_fds > 0) {
 227         for (int i = 0; i < msg->num_fds; i++) {
 228             if (fcntl(msg->fds[i], F_GETFL) == -1) {
 229                 return false;
 230             }
 231         }
 232     }
 233
 234      /* Verify message specific fields. */
 235     switch (msg->cmd) {
 236     case MPQEMU_CMD_SYNC_SYSMEM:
 237         if (msg->num_fds == 0 || msg->size != sizeof(SyncSysmemMsg)) {
 238             return false;
 239         }
 240         break;
 241     case MPQEMU_CMD_PCI_CFGWRITE:
 242     case MPQEMU_CMD_PCI_CFGREAD:
 243         if (msg->size != sizeof(PciConfDataMsg)) {
 244             return false;
 245         }
 246         break;
 247     case MPQEMU_CMD_BAR_WRITE:
 248     case MPQEMU_CMD_BAR_READ:
 249         if ((msg->size != sizeof(BarAccessMsg)) || (msg->num_fds != 0)) {
 250             return false;
 251         }
 252         break;
 253     case MPQEMU_CMD_SET_IRQFD:
 254         if (msg->size || (msg->num_fds != 2)) {
 255             return false;
 256         }
 257         break;
 258     default:
 259         break;
 260     }
 261
 262     return true;
 263 }