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lguest: documentation update

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Went through the documentation doing typo and content fixes.  This
patch contains only comment and whitespace changes.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2007-10-25 15:02:50 +10:00
parent 568a17ffce
commit e1e72965ec
16 changed files with 414 additions and 266 deletions
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48
drivers/lguest/segments.c
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@@ -12,8 +12,6 @@
#include "lg.h"
/*H:600
* We've almost completed the Host; there's just one file to go!
*
* Segments & The Global Descriptor Table
*
* (That title sounds like a bad Nerdcore group. Not to suggest that there are
@@ -55,7 +53,7 @@ static int ignored_gdt(unsigned int num)
|| num == GDT_ENTRY_DOUBLEFAULT_TSS);
}
/*H:610 Once the GDT has been changed, we fix the new entries up a little. We
/*H:630 Once the Guest gave us new GDT entries, we fix them up a little. We
* don't care if they're invalid: the worst that can happen is a General
* Protection Fault in the Switcher when it restores a Guest segment register
* which tries to use that entry. Then we kill the Guest for causing such a
@@ -84,25 +82,33 @@ static void fixup_gdt_table(struct lguest *lg, unsigned start, unsigned end)
}
}
/* This routine is called at boot or modprobe time for each CPU to set up the
* "constant" GDT entries for Guests running on that CPU. */
/*H:610 Like the IDT, we never simply use the GDT the Guest gives us. We keep
* a GDT for each CPU, and copy across the Guest's entries each time we want to
* run the Guest on that CPU.
*
* This routine is called at boot or modprobe time for each CPU to set up the
* constant GDT entries: the ones which are the same no matter what Guest we're
* running. */
void setup_default_gdt_entries(struct lguest_ro_state *state)
{
struct desc_struct *gdt = state->guest_gdt;
unsigned long tss = (unsigned long)&state->guest_tss;
/* The hypervisor segments are full 0-4G segments, privilege level 0 */
/* The Switcher segments are full 0-4G segments, privilege level 0 */
gdt[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;
gdt[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;
/* The TSS segment refers to the TSS entry for this CPU, so we cannot
* copy it from the Guest. Forgive the magic flags */
/* The TSS segment refers to the TSS entry for this particular CPU.
* Forgive the magic flags: the 0x8900 means the entry is Present, it's
* privilege level 0 Available 386 TSS system segment, and the 0x67
* means Saturn is eclipsed by Mercury in the twelfth house. */
gdt[GDT_ENTRY_TSS].a = 0x00000067 | (tss << 16);
gdt[GDT_ENTRY_TSS].b = 0x00008900 | (tss & 0xFF000000)
| ((tss >> 16) & 0x000000FF);
}
/* This routine is called before the Guest is run for the first time. */
/* This routine sets up the initial Guest GDT for booting. All entries start
* as 0 (unusable). */
void setup_guest_gdt(struct lguest *lg)
{
/* Start with full 0-4G segments... */
@@ -114,13 +120,8 @@ void setup_guest_gdt(struct lguest *lg)
lg->arch.gdt[GDT_ENTRY_KERNEL_DS].b |= (GUEST_PL << 13);
}
/* Like the IDT, we never simply use the GDT the Guest gives us. We set up the
* GDTs for each CPU, then we copy across the entries each time we want to run
* a different Guest on that CPU. */
/* A partial GDT load, for the three "thead-local storage" entries. Otherwise
* it's just like load_guest_gdt(). So much, in fact, it would probably be
* neater to have a single hypercall to cover both. */
/*H:650 An optimization of copy_gdt(), for just the three "thead-local storage"
* entries. */
void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt)
{
unsigned int i;
@@ -129,7 +130,9 @@ void copy_gdt_tls(const struct lguest *lg, struct desc_struct *gdt)
gdt[i] = lg->arch.gdt[i];
}
/* This is the full version */
/*H:640 When the Guest is run on a different CPU, or the GDT entries have
* changed, copy_gdt() is called to copy the Guest's GDT entries across to this
* CPU's GDT. */
void copy_gdt(const struct lguest *lg, struct desc_struct *gdt)
{
unsigned int i;
@@ -141,7 +144,8 @@ void copy_gdt(const struct lguest *lg, struct desc_struct *gdt)
gdt[i] = lg->arch.gdt[i];
}
/* This is where the Guest asks us to load a new GDT (LHCALL_LOAD_GDT). */
/*H:620 This is where the Guest asks us to load a new GDT (LHCALL_LOAD_GDT).
* We copy it from the Guest and tweak the entries. */
void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num)
{
/* We assume the Guest has the same number of GDT entries as the
@@ -157,16 +161,22 @@ void load_guest_gdt(struct lguest *lg, unsigned long table, u32 num)
lg->changed |= CHANGED_GDT;
}
/* This is the fast-track version for just changing the three TLS entries.
* Remember that this happens on every context switch, so it's worth
* optimizing. But wouldn't it be neater to have a single hypercall to cover
* both cases? */
void guest_load_tls(struct lguest *lg, unsigned long gtls)
{
struct desc_struct *tls = &lg->arch.gdt[GDT_ENTRY_TLS_MIN];
__lgread(lg, tls, gtls, sizeof(*tls)*GDT_ENTRY_TLS_ENTRIES);
fixup_gdt_table(lg, GDT_ENTRY_TLS_MIN, GDT_ENTRY_TLS_MAX+1);
/* Note that just the TLS entries have changed. */
lg->changed |= CHANGED_GDT_TLS;
}
/*:*/
/*
/*H:660
* With this, we have finished the Host.
*
* Five of the seven parts of our task are complete. You have made it through