/*P:500
* Just as userspace programs request kernel operations through a system
* call, the Guest requests Host operations through a "hypercall". You might
* notice this nomenclature doesn't really follow any logic, but the name has
* been around for long enough that we're stuck with it. As you'd expect, this
* code is basically a one big switch statement.
:*/
/* Copyright (C) 2006 Rusty Russell IBM Corporation
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/mm.h>
#include <linux/ktime.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include "lg.h"
/*H:120
* This is the core hypercall routine: where the Guest gets what it wants.
* Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both.
*/
static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
{
switch (args->arg0) {
case LHCALL_FLUSH_ASYNC:
/*
* This call does nothing, except by breaking out of the Guest
* it makes us process all the asynchronous hypercalls.
*/
break;
case LHCALL_SEND_INTERRUPTS:
/*
* This call does nothing too, but by breaking out of the Guest
* it makes us process any pending interrupts.
*/
break;
case LHCALL_LGUEST_INIT:
/*
* You can't get here unless you're already initialized. Don't
* do that.
*/
kill_guest(cpu, "already have lguest_data");
break;
case LHCALL_SHUTDOWN: {
char msg[128];
/*
* Shutdown is such a trivial hypercall that we do it in five
* lines right here.
*
* If the lgread fails, it will call kill_guest() itself; the
* kill_guest() with the message will be ignored.
*/
__lgread(cpu, msg, args->arg1, sizeof(msg));
msg[sizeof(msg)-1] = '\0';
kill_guest(cpu, "CRASH: %s", msg);
if (args->arg2 == LGUEST_SHUTDOWN_RESTART)
cpu->lg->dead = ERR_PTR(-ERESTART);
break;
}
case LHCALL_FLUSH_TLB:
/* FLUSH_TLB comes in two flavors, depending on the argument: */
if (args->arg1)
guest_pagetable_clear_all(cpu);
else
guest_pagetable_flush_user(cpu);
break;
/*
* All these calls simply pass the arguments through to the right
* routines.
*/
case LHCALL_NEW_PGTABLE:
guest_new_pagetable(cpu, args->arg1);
break;
case LHCALL_SET_STACK:
guest_set_stack(cpu, args->arg1, args->arg2, args->arg3);
break;
case LHCALL_SET_PTE:
#ifdef [31mCONFIG_X86_PAE[0m
guest_set_pte(cpu, args->arg1, args->arg2,
__pte(args->arg3 | (u64)args->arg4 << 32));
#else
guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3));
#endif
break;
case LHCALL_SET_PGD:
guest_set_pgd(cpu->lg, args->arg1, args->arg2);
break;
#ifdef [31mCONFIG_X86_PAE[0m
case LHCALL_SET_PMD:
guest_set_pmd(cpu->lg, args->arg1, args->arg2);
break;
#endif
case LHCALL_SET_CLOCKEVENT:
guest_set_clockevent(cpu, args->arg1);
break;
case LHCALL_HALT:
/* Similarly, this sets the halted flag for run_guest(). */
cpu->halted = 1;
break;
default:
/* It should be an architecture-specific hypercall. */
if (lguest_arch_do_hcall(cpu, args))
kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
}
}
/*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.trap)
break;
}
}
/*
* Last of all, we look at what happens first of all. The very first time the
* Guest makes a hypercall, we end up here to set things up:
*/
static void initialize(struct lg_cpu *cpu)
{
/*
* You can't do anything until you're initialized. The Guest knows the
* rules, so we're unforgiving here.
*/
if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
return;
}
if (lguest_arch_init_hypercalls(cpu))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
/*
* The Guest tells us where we're not to deliver interrupts by putting
* the instruction address into "struct lguest_data".
*/
if (get_user(cpu->lg->noirq_iret, &cpu->lg->lguest_data->noirq_iret))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
/*
* We write the current time into the Guest's data page once so it can
* set its clock.
*/
write_timestamp(cpu);
/* page_tables.c will also do some setup. */
page_table_guest_data_init(cpu);
/*
* This is the one case where the above accesses might have been the
* first write to a Guest page. This may have caused a copy-on-write
* fault, but the old page might be (read-only) in the Guest
* pagetable.
*/
guest_pagetable_clear_all(cpu);
}
/*:*/
/*M:013
* If a Guest reads from a page (so creates a mapping) that it has never
* written to, and then the Launcher writes to it (ie. the output of a virtual
* device), the Guest will still see the old page. In practice, this never
* happens: why would the Guest read a page which it has never written to? But
* a similar scenario might one day bite us, so it's worth mentioning.
*
* Note that if we used a shared anonymous mapping in the Launcher instead of
* mapping /dev/zero private, we wouldn't worry about cop-on-write. And we
* need that to switch the Launcher to processes (away from threads) anyway.
:*/
/*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.trap) {
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;
}
}
/*
* This routine supplies the Guest with time: it's used for wallclock time at
* initial boot and as a rough time source if the TSC isn't available.
*/
void write_timestamp(struct lg_cpu *cpu)
{
struct timespec now;
ktime_get_real_ts(&now);
if (copy_to_user(&cpu->lg->lguest_data->time,
&now, sizeof(struct timespec)))
kill_guest(cpu, "Writing timestamp");
}