/*H:100
* Hypercalls
*
* Remember from the Guest, hypercalls come in two flavors: normal and
* asynchronous. This file handles both of types.
*/
void do_hypercalls(struct lg_cpu *cpu)
{
/* Not initialized yet? This hypercall must do it. */
if (unlikely(!cpu->lg->lguest_data)) {
/* Set up the "struct lguest_data" */
initialize(cpu);
/* Hcall is done. */
cpu->hcall = NULL;
return;
}
/* The Guest has initialized.
*
* Look in the hypercall ring for the async hypercalls: */
do_async_hcalls(cpu);
/* If we stopped reading the hypercall ring because the Guest did a
* NOTIFY to the Launcher, we want to return now. Otherwise we do
* the hypercall. */
if (!cpu->pending_notify) {
do_hcall(cpu, cpu->hcall);
/* Tricky point: we reset the hcall pointer to mark the
* hypercall as "done". We use the hcall pointer rather than
* the trap number to indicate a hypercall is pending.
* Normally it doesn't matter: the Guest will run again and
* update the trap number before we come back here.
*
* However, if we are signalled or the Guest sends I/O to the
* Launcher, the run_guest() loop will exit without running the
* Guest. When it comes back it would try to re-run the
* hypercall. Finding that bug sucked. */
cpu->hcall = NULL;
}
}
/*H:124
* Asynchronous hypercalls are easy: we just look in the array in the
* Guest's "struct lguest_data" to see if any new ones are marked "ready".
*
* We are careful to do these in order: obviously we respect the order the
* Guest put them in the ring, but we also promise the Guest that they will
* happen before any normal hypercall (which is why we check this before
* checking for a normal hcall).
*/
static void do_async_hcalls(struct lg_cpu *cpu)
{
unsigned int i;
u8 st[LHCALL_RING_SIZE];
/* For simplicity, we copy the entire call status array in at once. */
if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st)))
return;
/* We process "struct lguest_data"s hcalls[] ring once. */
for (i = 0; i < ARRAY_SIZE(st); i++) {
struct hcall_args args;
/*
* We remember where we were up to from last time. This makes
* sure that the hypercalls are done in the order the Guest
* places them in the ring.
*/
unsigned int n = cpu->next_hcall;
/* 0xFF means there's no call here (yet). */
if (st[n] == 0xFF)
break;
/*
* OK, we have hypercall. Increment the "next_hcall" cursor,
* and wrap back to 0 if we reach the end.
*/
if (++cpu->next_hcall == LHCALL_RING_SIZE)
cpu->next_hcall = 0;
/*
* Copy the hypercall arguments into a local copy of the
* hcall_args struct.
*/
if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
sizeof(struct hcall_args))) {
kill_guest(cpu, "Fetching async hypercalls");
break;
}
/* Do the hypercall, same as a normal one. */
do_hcall(cpu, &args);
/* Mark the hypercall done. */
if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
kill_guest(cpu, "Writing result for async hypercall");
break;
}
/*
* Stop doing hypercalls if they want to notify the Launcher:
* it needs to service this first.
*/
if (cpu->pending_notify)
break;
}
}
void do_hypercalls(struct lg_cpu *cpu)
{
if (unlikely(!cpu->lg->lguest_data)) {
initialize(cpu);
cpu->hcall = NULL;
return;
}
do_async_hcalls(cpu);
if (!cpu->pending_notify) {
do_hcall(cpu, cpu->hcall);
cpu->hcall = NULL;
}
}
static void do_async_hcalls(struct lg_cpu *cpu)
{
unsigned int i;
u8 st[LHCALL_RING_SIZE];
if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st)))
return;
for (i = 0; i < ARRAY_SIZE(st); i++) {
struct hcall_args args;
unsigned int n = cpu->next_hcall;
if (st[n] == 0xFF)
break;
if (++cpu->next_hcall == LHCALL_RING_SIZE)
cpu->next_hcall = 0;
if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
sizeof(struct hcall_args))) {
kill_guest(cpu, "Fetching async hypercalls");
break;
}
do_hcall(cpu, &args);
if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
kill_guest(cpu, "Writing result for async hypercall");
break;
}
if (cpu->pending_notify)
break;
}
}
