lguest: comment documentation update.

[linux-2.6-omap-h63xx.git] / drivers / lguest / x86 / core.c

diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index 635187812d52b11cf85ed65a3ae88ef6fabf6f7f..5126d5d9ea0e8d8d97fa0eaf47ed22216329328b 100644 (file)
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -17,6 +17,13 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */
+/*P:450 This file contains the x86-specific lguest code.  It used to be all
+ * mixed in with drivers/lguest/core.c but several foolhardy code slashers
+ * wrestled most of the dependencies out to here in preparation for porting
+ * lguest to other architectures (see what I mean by foolhardy?).
+ *
+ * This also contains a couple of non-obvious setup and teardown pieces which
+ * were implemented after days of debugging pain. :*/
 #include <linux/kernel.h>
 #include <linux/start_kernel.h>
 #include <linux/string.h>
@@ -157,6 +164,8 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages)
  * also simplify copy_in_guest_info().  Note that we'd still need to restore
  * things when we exit to Launcher userspace, but that's fairly easy.
  *
+ * We could also try using this hooks for PGE, but that might be too expensive.
+ *
  * The hooks were designed for KVM, but we can also put them to good use. :*/
 
 /*H:040 This is the i386-specific code to setup and run the Guest.  Interrupts
@@ -182,7 +191,7 @@ void lguest_arch_run_guest(struct lg_cpu *cpu)
         * was doing. */
        run_guest_once(cpu, lguest_pages(raw_smp_processor_id()));
 
-       /* Note that the "regs" pointer contains two extra entries which are
+       /* Note that the "regs" structure contains two extra entries which are
         * not really registers: a trap number which says what interrupt or
         * trap made the switcher code come back, and an error code which some
         * traps set.  */
@@ -293,11 +302,10 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
                break;
        case 14: /* We've intercepted a Page Fault. */
                /* The Guest accessed a virtual address that wasn't mapped.
-                * This happens a lot: we don't actually set up most of the
-                * page tables for the Guest at all when we start: as it runs
-                * it asks for more and more, and we set them up as
-                * required. In this case, we don't even tell the Guest that
-                * the fault happened.
+                * This happens a lot: we don't actually set up most of the page
+                * tables for the Guest at all when we start: as it runs it asks
+                * for more and more, and we set them up as required. In this
+                * case, we don't even tell the Guest that the fault happened.
                 *
                 * The errcode tells whether this was a read or a write, and
                 * whether kernel or userspace code. */
@@ -342,7 +350,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
        if (!deliver_trap(cpu, cpu->regs->trapnum))
                /* If the Guest doesn't have a handler (either it hasn't
                 * registered any yet, or it's one of the faults we don't let
-                * it handle), it dies with a cryptic error message. */
+                * it handle), it dies with this cryptic error message. */
                kill_guest(cpu, "unhandled trap %li at %#lx (%#lx)",
                           cpu->regs->trapnum, cpu->regs->eip,
                           cpu->regs->trapnum == 14 ? cpu->arch.last_pagefault
@@ -375,8 +383,8 @@ void __init lguest_arch_host_init(void)
         * The only exception is the interrupt handlers in switcher.S: their
         * addresses are placed in a table (default_idt_entries), so we need to
         * update the table with the new addresses.  switcher_offset() is a
-        * convenience function which returns the distance between the builtin
-        * switcher code and the high-mapped copy we just made. */
+        * convenience function which returns the distance between the
+        * compiled-in switcher code and the high-mapped copy we just made. */
        for (i = 0; i < IDT_ENTRIES; i++)
                default_idt_entries[i] += switcher_offset();
 
@@ -416,7 +424,7 @@ void __init lguest_arch_host_init(void)
                state->guest_gdt_desc.address = (long)&state->guest_gdt;
 
                /* We know where we want the stack to be when the Guest enters
-                * the switcher: in pages->regs.  The stack grows upwards, so
+                * the Switcher: in pages->regs.  The stack grows upwards, so
                 * we start it at the end of that structure. */
                state->guest_tss.sp0 = (long)(&pages->regs + 1);
                /* And this is the GDT entry to use for the stack: we keep a
@@ -513,8 +521,8 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu)
 {
        u32 tsc_speed;
 
-       /* The pointer to the Guest's "struct lguest_data" is the only
-        * argument.  We check that address now. */
+       /* The pointer to the Guest's "struct lguest_data" is the only argument.
+        * We check that address now. */
        if (!lguest_address_ok(cpu->lg, cpu->hcall->arg1,
                               sizeof(*cpu->lg->lguest_data)))
                return -EFAULT;
@@ -546,6 +554,7 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu)
 
        return 0;
 }
+/*:*/
 
 /*L:030 lguest_arch_setup_regs()
  *