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lguest: fix comment style

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I don't really notice it (except to begrudge the extra vertical
space), but Ingo does.  And he pointed out that one excuse of lguest
is as a teaching tool, it should set a good example.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@redhat.com>
This commit is contained in:
Rusty Russell
2009-07-30 16:03:45 -06:00
parent e969fed542
commit 2e04ef7691
17 changed files with 1906 additions and 1015 deletions
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141
drivers/lguest/hypercalls.c
View File

@@ -1,8 +1,10 @@
/*P:500 Just as userspace programs request kernel operations through a system
/*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. :*/
* code is basically a one big switch statement.
:*/
/* Copyright (C) 2006 Rusty Russell IBM Corporation
@@ -28,30 +30,41 @@
#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. */
/*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. */
/*
* 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. */
/*
* 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. */
/*
* 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: {
/* Shutdown is such a trivial hypercall that we do it in four
* lines right here. */
char msg[128];
/* If the lgread fails, it will call kill_guest() itself; the
* kill_guest() with the message will be ignored. */
/*
* Shutdown is such a trivial hypercall that we do it in four
* 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);
@@ -60,16 +73,17 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
break;
}
case LHCALL_FLUSH_TLB:
/* FLUSH_TLB comes in two flavors, depending on the
* argument: */
/* 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. */
/*
* All these calls simply pass the arguments through to the right
* routines.
*/
case LHCALL_NEW_PGTABLE:
guest_new_pagetable(cpu, args->arg1);
break;
@@ -112,15 +126,16 @@ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args)
kill_guest(cpu, "Bad hypercall %li\n", args->arg0);
}
}
/*:*/
/*H:124 Asynchronous hypercalls are easy: we just look in the array in the
/*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). */
* checking for a normal hcall).
*/
static void do_async_hcalls(struct lg_cpu *cpu)
{
unsigned int i;
@@ -133,22 +148,28 @@ static void do_async_hcalls(struct lg_cpu *cpu)
/* 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
/*
* 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. */
* 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. */
/*
* 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. */
/*
* 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");
@@ -164,19 +185,25 @@ static void do_async_hcalls(struct lg_cpu *cpu)
break;
}
/* Stop doing hypercalls if they want to notify the Launcher:
* it needs to service this first. */
/*
* 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: */
/*
* 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. */
/*
* 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;
@@ -185,32 +212,40 @@ static void initialize(struct lg_cpu *cpu)
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". */
/*
* 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. */
/*
* 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
/*
* 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. */
* pagetable.
*/
guest_pagetable_clear_all(cpu);
}
/*:*/
/*M:013 If a Guest reads from a page (so creates a mapping) that it has never
/*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. :*/
* a similar scenario might one day bite us, so it's worth mentioning.
:*/
/*H:100
* Hypercalls
@@ -229,17 +264,22 @@ void do_hypercalls(struct lg_cpu *cpu)
return;
}
/* The Guest has initialized.
/*
* The Guest has initialized.
*
* Look in the hypercall ring for the async hypercalls: */
* 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
/*
* 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. */
* the hypercall.
*/
if (!cpu->pending_notify) {
do_hcall(cpu, cpu->hcall);
/* Tricky point: we reset the hcall pointer to mark the
/*
* 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
@@ -248,13 +288,16 @@ void do_hypercalls(struct lg_cpu *cpu)
* 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. */
* 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. */
/*
* 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;