/*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 #include #include #include #include #include #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; case LHCALL_NOTIFY: cpu->pending_notify = args->arg1; 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_notify) 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 range of addresses into "struct lguest_data". */ if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start) || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end)) 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_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; } } /* * 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"); }