313 lines
9.3 KiB
C
313 lines
9.3 KiB
C
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/*P:500
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* Just as userspace programs request kernel operations through a system
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* call, the Guest requests Host operations through a "hypercall". You might
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* notice this nomenclature doesn't really follow any logic, but the name has
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* been around for long enough that we're stuck with it. As you'd expect, this
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* code is basically a one big switch statement.
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:*/
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/* Copyright (C) 2006 Rusty Russell IBM Corporation
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <linux/uaccess.h>
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#include <linux/syscalls.h>
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#include <linux/mm.h>
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#include <linux/ktime.h>
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#include <asm/page.h>
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#include <asm/pgtable.h>
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#include "lg.h"
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/*H:120
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* This is the core hypercall routine: where the Guest gets what it wants.
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* Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both.
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*/
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static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
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{
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switch (args->arg0) {
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case LHCALL_FLUSH_ASYNC:
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/*
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* This call does nothing, except by breaking out of the Guest
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* it makes us process all the asynchronous hypercalls.
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*/
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break;
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case LHCALL_SEND_INTERRUPTS:
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/*
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* This call does nothing too, but by breaking out of the Guest
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* it makes us process any pending interrupts.
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*/
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break;
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case LHCALL_LGUEST_INIT:
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/*
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* You can't get here unless you're already initialized. Don't
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* do that.
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*/
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kill_guest(cpu, "already have lguest_data");
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break;
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case LHCALL_SHUTDOWN: {
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char msg[128];
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/*
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* Shutdown is such a trivial hypercall that we do it in five
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* lines right here.
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*
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* If the lgread fails, it will call kill_guest() itself; the
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* kill_guest() with the message will be ignored.
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*/
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__lgread(cpu, msg, args->arg1, sizeof(msg));
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msg[sizeof(msg)-1] = '\0';
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kill_guest(cpu, "CRASH: %s", msg);
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if (args->arg2 == LGUEST_SHUTDOWN_RESTART)
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cpu->lg->dead = ERR_PTR(-ERESTART);
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break;
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}
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case LHCALL_FLUSH_TLB:
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/* FLUSH_TLB comes in two flavors, depending on the argument: */
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if (args->arg1)
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guest_pagetable_clear_all(cpu);
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else
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guest_pagetable_flush_user(cpu);
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break;
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/*
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* All these calls simply pass the arguments through to the right
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* routines.
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*/
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case LHCALL_NEW_PGTABLE:
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guest_new_pagetable(cpu, args->arg1);
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break;
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case LHCALL_SET_STACK:
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guest_set_stack(cpu, args->arg1, args->arg2, args->arg3);
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break;
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case LHCALL_SET_PTE:
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#ifdef CONFIG_X86_PAE
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guest_set_pte(cpu, args->arg1, args->arg2,
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__pte(args->arg3 | (u64)args->arg4 << 32));
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#else
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guest_set_pte(cpu, args->arg1, args->arg2, __pte(args->arg3));
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#endif
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break;
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case LHCALL_SET_PGD:
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guest_set_pgd(cpu->lg, args->arg1, args->arg2);
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break;
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#ifdef CONFIG_X86_PAE
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case LHCALL_SET_PMD:
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guest_set_pmd(cpu->lg, args->arg1, args->arg2);
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break;
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#endif
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case LHCALL_SET_CLOCKEVENT:
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guest_set_clockevent(cpu, args->arg1);
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break;
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case LHCALL_TS:
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/* This sets the TS flag, as we saw used in run_guest(). */
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cpu->ts = args->arg1;
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break;
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case LHCALL_HALT:
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/* Similarly, this sets the halted flag for run_guest(). */
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cpu->halted = 1;
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break;
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case LHCALL_NOTIFY:
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cpu->pending_notify = args->arg1;
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break;
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default:
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/* It should be an architecture-specific hypercall. */
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if (lguest_arch_do_hcall(cpu, args))
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kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
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}
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}
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/*H:124
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* Asynchronous hypercalls are easy: we just look in the array in the
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* Guest's "struct lguest_data" to see if any new ones are marked "ready".
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*
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* We are careful to do these in order: obviously we respect the order the
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* Guest put them in the ring, but we also promise the Guest that they will
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* happen before any normal hypercall (which is why we check this before
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* checking for a normal hcall).
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*/
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static void do_async_hcalls(struct lg_cpu *cpu)
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{
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unsigned int i;
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u8 st[LHCALL_RING_SIZE];
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/* For simplicity, we copy the entire call status array in at once. */
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if (copy_from_user(&st, &cpu->lg->lguest_data->hcall_status, sizeof(st)))
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return;
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/* We process "struct lguest_data"s hcalls[] ring once. */
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for (i = 0; i < ARRAY_SIZE(st); i++) {
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struct hcall_args args;
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/*
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* We remember where we were up to from last time. This makes
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* sure that the hypercalls are done in the order the Guest
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* places them in the ring.
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*/
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unsigned int n = cpu->next_hcall;
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/* 0xFF means there's no call here (yet). */
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if (st[n] == 0xFF)
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break;
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/*
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* OK, we have hypercall. Increment the "next_hcall" cursor,
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* and wrap back to 0 if we reach the end.
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*/
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if (++cpu->next_hcall == LHCALL_RING_SIZE)
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cpu->next_hcall = 0;
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/*
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* Copy the hypercall arguments into a local copy of the
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* hcall_args struct.
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*/
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if (copy_from_user(&args, &cpu->lg->lguest_data->hcalls[n],
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sizeof(struct hcall_args))) {
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kill_guest(cpu, "Fetching async hypercalls");
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break;
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}
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/* Do the hypercall, same as a normal one. */
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do_hcall(cpu, &args);
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/* Mark the hypercall done. */
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if (put_user(0xFF, &cpu->lg->lguest_data->hcall_status[n])) {
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kill_guest(cpu, "Writing result for async hypercall");
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break;
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}
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/*
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* Stop doing hypercalls if they want to notify the Launcher:
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* it needs to service this first.
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*/
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if (cpu->pending_notify)
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break;
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}
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}
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/*
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* Last of all, we look at what happens first of all. The very first time the
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* Guest makes a hypercall, we end up here to set things up:
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*/
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static void initialize(struct lg_cpu *cpu)
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{
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/*
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* You can't do anything until you're initialized. The Guest knows the
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* rules, so we're unforgiving here.
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*/
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if (cpu->hcall->arg0 != LHCALL_LGUEST_INIT) {
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kill_guest(cpu, "hypercall %li before INIT", cpu->hcall->arg0);
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return;
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}
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if (lguest_arch_init_hypercalls(cpu))
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kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
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/*
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* The Guest tells us where we're not to deliver interrupts by putting
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* the range of addresses into "struct lguest_data".
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*/
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if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
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|| get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
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kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
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/*
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* We write the current time into the Guest's data page once so it can
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* set its clock.
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*/
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write_timestamp(cpu);
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/* page_tables.c will also do some setup. */
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page_table_guest_data_init(cpu);
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/*
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* This is the one case where the above accesses might have been the
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* first write to a Guest page. This may have caused a copy-on-write
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* fault, but the old page might be (read-only) in the Guest
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* pagetable.
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*/
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guest_pagetable_clear_all(cpu);
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}
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/*:*/
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/*M:013
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* If a Guest reads from a page (so creates a mapping) that it has never
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* written to, and then the Launcher writes to it (ie. the output of a virtual
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* device), the Guest will still see the old page. In practice, this never
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* happens: why would the Guest read a page which it has never written to? But
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* a similar scenario might one day bite us, so it's worth mentioning.
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*
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* Note that if we used a shared anonymous mapping in the Launcher instead of
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* mapping /dev/zero private, we wouldn't worry about cop-on-write. And we
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* need that to switch the Launcher to processes (away from threads) anyway.
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:*/
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/*H:100
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* Hypercalls
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*
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* Remember from the Guest, hypercalls come in two flavors: normal and
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* asynchronous. This file handles both of types.
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*/
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void do_hypercalls(struct lg_cpu *cpu)
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{
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/* Not initialized yet? This hypercall must do it. */
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if (unlikely(!cpu->lg->lguest_data)) {
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/* Set up the "struct lguest_data" */
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initialize(cpu);
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/* Hcall is done. */
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cpu->hcall = NULL;
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return;
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}
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/*
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* The Guest has initialized.
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*
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* Look in the hypercall ring for the async hypercalls:
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*/
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do_async_hcalls(cpu);
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/*
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* If we stopped reading the hypercall ring because the Guest did a
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* NOTIFY to the Launcher, we want to return now. Otherwise we do
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* the hypercall.
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*/
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if (!cpu->pending_notify) {
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do_hcall(cpu, cpu->hcall);
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/*
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* Tricky point: we reset the hcall pointer to mark the
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* hypercall as "done". We use the hcall pointer rather than
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* the trap number to indicate a hypercall is pending.
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* Normally it doesn't matter: the Guest will run again and
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* update the trap number before we come back here.
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*
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* However, if we are signalled or the Guest sends I/O to the
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* Launcher, the run_guest() loop will exit without running the
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* Guest. When it comes back it would try to re-run the
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* hypercall. Finding that bug sucked.
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*/
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cpu->hcall = NULL;
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}
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}
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/*
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* This routine supplies the Guest with time: it's used for wallclock time at
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* initial boot and as a rough time source if the TSC isn't available.
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*/
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void write_timestamp(struct lg_cpu *cpu)
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{
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struct timespec now;
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ktime_get_real_ts(&now);
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if (copy_to_user(&cpu->lg->lguest_data->time,
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&now, sizeof(struct timespec)))
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kill_guest(cpu, "Writing timestamp");
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}
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