--- /dev/null
+/*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 CONFIG_X86_PAE
+ 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 CONFIG_X86_PAE
+ 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_TS:
+ /* This sets the TS flag, as we saw used in run_guest(). */
+ cpu->ts = 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");
+}
Code Review / kvmfornfv.git / blobdiff