lguest: write more information to userspace about pending traps.

This is preparation for userspace handling MMIO and ioport accesses.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/core.c

@@ -229,16 +229,17 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
 		 * It's possible the Guest did a NOTIFY hypercall to the
 		 * Launcher.
 		 */
-		if (cpu->pending_notify) {
+		if (cpu->pending.trap) {
 			/*
 			 * Does it just needs to write to a registered
 			 * eventfd (ie. the appropriate virtqueue thread)?
 			 */
 			if (!send_notify_to_eventfd(cpu)) {
 				/* OK, we tell the main Launcher. */
-				if (put_user(cpu->pending_notify, user))
+				if (copy_to_user(user, &cpu->pending,
+						 sizeof(cpu->pending)))
 					return -EFAULT;
-				return sizeof(cpu->pending_notify);
+				return sizeof(cpu->pending);
 			}
 		}
 

drivers/lguest/hypercalls.c

@@ -118,7 +118,8 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
 		cpu->halted = 1;
 		break;
 	case LHCALL_NOTIFY:
-		cpu->pending_notify = args->arg1;
+		cpu->pending.trap = LGUEST_TRAP_ENTRY;
+		cpu->pending.addr = args->arg1;
 		break;
 	default:
 		/* It should be an architecture-specific hypercall. */
@@ -189,7 +190,7 @@ static void do_async_hcalls(struct lg_cpu *cpu)
 		 * Stop doing hypercalls if they want to notify the Launcher:
 		 * it needs to service this first.
 		 */
-		if (cpu->pending_notify)
+		if (cpu->pending.trap)
 			break;
 	}
 }
@@ -280,7 +281,7 @@ void do_hypercalls(struct lg_cpu *cpu)
 	 * NOTIFY to the Launcher, we want to return now.  Otherwise we do
 	 * the hypercall.
 	 */
-	if (!cpu->pending_notify) {
+	if (!cpu->pending.trap) {
 		do_hcall(cpu, cpu->hcall);
 		/*
 		 * Tricky point: we reset the hcall pointer to mark the

drivers/lguest/lg.h

@@ -50,7 +50,8 @@ struct lg_cpu {
 	/* Bitmap of what has changed: see CHANGED_* above. */
 	int changed;
 
-	unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */
+	/* Pending operation. */
+	struct lguest_pending pending;
 
 	unsigned long *reg_read; /* register from LHREQ_GETREG */
 

drivers/lguest/lguest_user.c

@@ -29,6 +29,10 @@ bool send_notify_to_eventfd(struct lg_cpu *cpu)
 	unsigned int i;
 	struct lg_eventfd_map *map;
 
+	/* We only connect LHCALL_NOTIFY to event fds, not other traps. */
+	if (cpu->pending.trap != LGUEST_TRAP_ENTRY)
+		return false;
+
 	/*
 	 * This "rcu_read_lock()" helps track when someone is still looking at
 	 * the (RCU-using) eventfds array.  It's not actually a lock at all;
@@ -52,9 +56,9 @@ bool send_notify_to_eventfd(struct lg_cpu *cpu)
 	 * we'll continue to use the old array and just won't see the new one.
 	 */
 	for (i = 0; i < map->num; i++) {
-		if (map->map[i].addr == cpu->pending_notify) {
+		if (map->map[i].addr == cpu->pending.addr) {
 			eventfd_signal(map->map[i].event, 1);
-			cpu->pending_notify = 0;
+			cpu->pending.trap = 0;
 			break;
 		}
 	}
@@ -62,7 +66,7 @@ bool send_notify_to_eventfd(struct lg_cpu *cpu)
 	rcu_read_unlock();
 
 	/* If we cleared the notification, it's because we found a match. */
-	return cpu->pending_notify == 0;
+	return cpu->pending.trap == 0;
 }
 
 /*L:055
@@ -282,8 +286,8 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
 	 * If we returned from read() last time because the Guest sent I/O,
 	 * clear the flag.
 	 */
-	if (cpu->pending_notify)
-		cpu->pending_notify = 0;
+	if (cpu->pending.trap)
+		cpu->pending.trap = 0;
 
 	/* Run the Guest until something interesting happens. */
 	return run_guest(cpu, (unsigned long __user *)user);

include/linux/lguest_launcher.h

@@ -67,6 +67,19 @@ enum lguest_req
 	LHREQ_SETREG, /* + offset within struct pt_regs, value. */
 };
 
+/*
+ * This is what read() of the lguest fd populates.  trap ==
+ * LGUEST_TRAP_ENTRY for an LHCALL_NOTIFY (addr is the
+ * argument), 14 for a page fault in the MMIO region (addr is
+ * the trap address, insn is the instruction), or 13 for a GPF
+ * (insn is the instruction).
+ */
+struct lguest_pending {
+	__u8 trap;
+	__u8 insn[7];
+	__u32 addr;
+};
+
 /*
  * The alignment to use between consumer and producer parts of vring.
  * x86 pagesize for historical reasons.

tools/lguest/lguest.c

@@ -1820,17 +1820,21 @@ static void __attribute__((noreturn)) restart_guest(void)
 static void __attribute__((noreturn)) run_guest(void)
 {
 	for (;;) {
-		unsigned long notify_addr;
+		struct lguest_pending notify;
 		int readval;
 
 		/* We read from the /dev/lguest device to run the Guest. */
-		readval = pread(lguest_fd, &notify_addr,
-				sizeof(notify_addr), cpu_id);
+		readval = pread(lguest_fd, &notify, sizeof(notify), cpu_id);
 
 		/* One unsigned long means the Guest did HCALL_NOTIFY */
-		if (readval == sizeof(notify_addr)) {
-			verbose("Notify on address %#lx\n", notify_addr);
-			handle_output(notify_addr);
+		if (readval == sizeof(notify)) {
+			if (notify.trap == 0x1F) {
+				verbose("Notify on address %#08x\n",
+					notify.addr);
+				handle_output(notify.addr);
+			} else
+				errx(1, "Unknown trap %i addr %#08x\n",
+				     notify.trap, notify.addr);
 		/* ENOENT means the Guest died.  Reading tells us why. */
 		} else if (errno == ENOENT) {
 			char reason[1024] = { 0 };