lguest: fix comment style
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>
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index a6fe1ab..3da902e 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -1,9 +1,11 @@
-/*P:700 The pagetable code, on the other hand, still shows the scars of
+/*P:700
+ * The pagetable code, on the other hand, still shows the scars of
* previous encounters. It's functional, and as neat as it can be in the
* circumstances, but be wary, for these things are subtle and break easily.
* The Guest provides a virtual to physical mapping, but we can neither trust
* it nor use it: we verify and convert it here then point the CPU to the
- * converted Guest pages when running the Guest. :*/
+ * converted Guest pages when running the Guest.
+:*/
/* Copyright (C) Rusty Russell IBM Corporation 2006.
* GPL v2 and any later version */
@@ -17,10 +19,12 @@
#include <asm/bootparam.h>
#include "lg.h"
-/*M:008 We hold reference to pages, which prevents them from being swapped.
+/*M:008
+ * We hold reference to pages, which prevents them from being swapped.
* It'd be nice to have a callback in the "struct mm_struct" when Linux wants
* to swap out. If we had this, and a shrinker callback to trim PTE pages, we
- * could probably consider launching Guests as non-root. :*/
+ * could probably consider launching Guests as non-root.
+:*/
/*H:300
* The Page Table Code
@@ -45,16 +49,19 @@
* (v) Flushing (throwing away) page tables,
* (vi) Mapping the Switcher when the Guest is about to run,
* (vii) Setting up the page tables initially.
- :*/
+:*/
-
-/* 1024 entries in a page table page maps 1024 pages: 4MB. The Switcher is
+/*
+ * 1024 entries in a page table page maps 1024 pages: 4MB. The Switcher is
* conveniently placed at the top 4MB, so it uses a separate, complete PTE
- * page. */
+ * page.
+ */
#define SWITCHER_PGD_INDEX (PTRS_PER_PGD - 1)
-/* For PAE we need the PMD index as well. We use the last 2MB, so we
- * will need the last pmd entry of the last pmd page. */
+/*
+ * For PAE we need the PMD index as well. We use the last 2MB, so we
+ * will need the last pmd entry of the last pmd page.
+ */
#ifdef CONFIG_X86_PAE
#define SWITCHER_PMD_INDEX (PTRS_PER_PMD - 1)
#define RESERVE_MEM 2U
@@ -64,13 +71,16 @@
#define CHECK_GPGD_MASK _PAGE_TABLE
#endif
-/* We actually need a separate PTE page for each CPU. Remember that after the
+/*
+ * We actually need a separate PTE page for each CPU. Remember that after the
* Switcher code itself comes two pages for each CPU, and we don't want this
- * CPU's guest to see the pages of any other CPU. */
+ * CPU's guest to see the pages of any other CPU.
+ */
static DEFINE_PER_CPU(pte_t *, switcher_pte_pages);
#define switcher_pte_page(cpu) per_cpu(switcher_pte_pages, cpu)
-/*H:320 The page table code is curly enough to need helper functions to keep it
+/*H:320
+ * The page table code is curly enough to need helper functions to keep it
* clear and clean.
*
* There are two functions which return pointers to the shadow (aka "real")
@@ -79,7 +89,8 @@
* spgd_addr() takes the virtual address and returns a pointer to the top-level
* page directory entry (PGD) for that address. Since we keep track of several
* page tables, the "i" argument tells us which one we're interested in (it's
- * usually the current one). */
+ * usually the current one).
+ */
static pgd_t *spgd_addr(struct lg_cpu *cpu, u32 i, unsigned long vaddr)
{
unsigned int index = pgd_index(vaddr);
@@ -96,9 +107,11 @@
}
#ifdef CONFIG_X86_PAE
-/* This routine then takes the PGD entry given above, which contains the
+/*
+ * This routine then takes the PGD entry given above, which contains the
* address of the PMD page. It then returns a pointer to the PMD entry for the
- * given address. */
+ * given address.
+ */
static pmd_t *spmd_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
{
unsigned int index = pmd_index(vaddr);
@@ -119,9 +132,11 @@
}
#endif
-/* This routine then takes the page directory entry returned above, which
+/*
+ * This routine then takes the page directory entry returned above, which
* contains the address of the page table entry (PTE) page. It then returns a
- * pointer to the PTE entry for the given address. */
+ * pointer to the PTE entry for the given address.
+ */
static pte_t *spte_addr(struct lg_cpu *cpu, pgd_t spgd, unsigned long vaddr)
{
#ifdef CONFIG_X86_PAE
@@ -139,8 +154,10 @@
return &page[pte_index(vaddr)];
}
-/* These two functions just like the above two, except they access the Guest
- * page tables. Hence they return a Guest address. */
+/*
+ * These two functions just like the above two, except they access the Guest
+ * page tables. Hence they return a Guest address.
+ */
static unsigned long gpgd_addr(struct lg_cpu *cpu, unsigned long vaddr)
{
unsigned int index = vaddr >> (PGDIR_SHIFT);
@@ -175,17 +192,21 @@
#endif
/*:*/
-/*M:014 get_pfn is slow: we could probably try to grab batches of pages here as
- * an optimization (ie. pre-faulting). :*/
+/*M:014
+ * get_pfn is slow: we could probably try to grab batches of pages here as
+ * an optimization (ie. pre-faulting).
+:*/
-/*H:350 This routine takes a page number given by the Guest and converts it to
+/*H:350
+ * This routine takes a page number given by the Guest and converts it to
* an actual, physical page number. It can fail for several reasons: the
* virtual address might not be mapped by the Launcher, the write flag is set
* and the page is read-only, or the write flag was set and the page was
* shared so had to be copied, but we ran out of memory.
*
* This holds a reference to the page, so release_pte() is careful to put that
- * back. */
+ * back.
+ */
static unsigned long get_pfn(unsigned long virtpfn, int write)
{
struct page *page;
@@ -198,33 +219,41 @@
return -1UL;
}
-/*H:340 Converting a Guest page table entry to a shadow (ie. real) page table
+/*H:340
+ * Converting a Guest page table entry to a shadow (ie. real) page table
* entry can be a little tricky. The flags are (almost) the same, but the
* Guest PTE contains a virtual page number: the CPU needs the real page
- * number. */
+ * number.
+ */
static pte_t gpte_to_spte(struct lg_cpu *cpu, pte_t gpte, int write)
{
unsigned long pfn, base, flags;
- /* The Guest sets the global flag, because it thinks that it is using
+ /*
+ * The Guest sets the global flag, because it thinks that it is using
* PGE. We only told it to use PGE so it would tell us whether it was
* flushing a kernel mapping or a userspace mapping. We don't actually
- * use the global bit, so throw it away. */
+ * use the global bit, so throw it away.
+ */
flags = (pte_flags(gpte) & ~_PAGE_GLOBAL);
/* The Guest's pages are offset inside the Launcher. */
base = (unsigned long)cpu->lg->mem_base / PAGE_SIZE;
- /* We need a temporary "unsigned long" variable to hold the answer from
+ /*
+ * We need a temporary "unsigned long" variable to hold the answer from
* get_pfn(), because it returns 0xFFFFFFFF on failure, which wouldn't
* fit in spte.pfn. get_pfn() finds the real physical number of the
- * page, given the virtual number. */
+ * page, given the virtual number.
+ */
pfn = get_pfn(base + pte_pfn(gpte), write);
if (pfn == -1UL) {
kill_guest(cpu, "failed to get page %lu", pte_pfn(gpte));
- /* When we destroy the Guest, we'll go through the shadow page
+ /*
+ * When we destroy the Guest, we'll go through the shadow page
* tables and release_pte() them. Make sure we don't think
- * this one is valid! */
+ * this one is valid!
+ */
flags = 0;
}
/* Now we assemble our shadow PTE from the page number and flags. */
@@ -234,8 +263,10 @@
/*H:460 And to complete the chain, release_pte() looks like this: */
static void release_pte(pte_t pte)
{
- /* Remember that get_user_pages_fast() took a reference to the page, in
- * get_pfn()? We have to put it back now. */
+ /*
+ * Remember that get_user_pages_fast() took a reference to the page, in
+ * get_pfn()? We have to put it back now.
+ */
if (pte_flags(pte) & _PAGE_PRESENT)
put_page(pte_page(pte));
}
@@ -273,7 +304,8 @@
* and return to the Guest without it knowing.
*
* If we fixed up the fault (ie. we mapped the address), this routine returns
- * true. Otherwise, it was a real fault and we need to tell the Guest. */
+ * true. Otherwise, it was a real fault and we need to tell the Guest.
+ */
bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
{
pgd_t gpgd;
@@ -298,22 +330,26 @@
if (!(pgd_flags(*spgd) & _PAGE_PRESENT)) {
/* No shadow entry: allocate a new shadow PTE page. */
unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
- /* This is not really the Guest's fault, but killing it is
- * simple for this corner case. */
+ /*
+ * This is not really the Guest's fault, but killing it is
+ * simple for this corner case.
+ */
if (!ptepage) {
kill_guest(cpu, "out of memory allocating pte page");
return false;
}
/* We check that the Guest pgd is OK. */
check_gpgd(cpu, gpgd);
- /* And we copy the flags to the shadow PGD entry. The page
- * number in the shadow PGD is the page we just allocated. */
+ /*
+ * And we copy the flags to the shadow PGD entry. The page
+ * number in the shadow PGD is the page we just allocated.
+ */
set_pgd(spgd, __pgd(__pa(ptepage) | pgd_flags(gpgd)));
}
#ifdef CONFIG_X86_PAE
gpmd = lgread(cpu, gpmd_addr(gpgd, vaddr), pmd_t);
- /* middle level not present? We can't map it in. */
+ /* Middle level not present? We can't map it in. */
if (!(pmd_flags(gpmd) & _PAGE_PRESENT))
return false;
@@ -324,8 +360,10 @@
/* No shadow entry: allocate a new shadow PTE page. */
unsigned long ptepage = get_zeroed_page(GFP_KERNEL);
- /* This is not really the Guest's fault, but killing it is
- * simple for this corner case. */
+ /*
+ * This is not really the Guest's fault, but killing it is
+ * simple for this corner case.
+ */
if (!ptepage) {
kill_guest(cpu, "out of memory allocating pte page");
return false;
@@ -334,17 +372,23 @@
/* We check that the Guest pmd is OK. */
check_gpmd(cpu, gpmd);
- /* And we copy the flags to the shadow PMD entry. The page
- * number in the shadow PMD is the page we just allocated. */
+ /*
+ * And we copy the flags to the shadow PMD entry. The page
+ * number in the shadow PMD is the page we just allocated.
+ */
native_set_pmd(spmd, __pmd(__pa(ptepage) | pmd_flags(gpmd)));
}
- /* OK, now we look at the lower level in the Guest page table: keep its
- * address, because we might update it later. */
+ /*
+ * OK, now we look at the lower level in the Guest page table: keep its
+ * address, because we might update it later.
+ */
gpte_ptr = gpte_addr(cpu, gpmd, vaddr);
#else
- /* OK, now we look at the lower level in the Guest page table: keep its
- * address, because we might update it later. */
+ /*
+ * OK, now we look at the lower level in the Guest page table: keep its
+ * address, because we might update it later.
+ */
gpte_ptr = gpte_addr(cpu, gpgd, vaddr);
#endif
gpte = lgread(cpu, gpte_ptr, pte_t);
@@ -353,8 +397,10 @@
if (!(pte_flags(gpte) & _PAGE_PRESENT))
return false;
- /* Check they're not trying to write to a page the Guest wants
- * read-only (bit 2 of errcode == write). */
+ /*
+ * Check they're not trying to write to a page the Guest wants
+ * read-only (bit 2 of errcode == write).
+ */
if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW))
return false;
@@ -362,8 +408,10 @@
if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER))
return false;
- /* Check that the Guest PTE flags are OK, and the page number is below
- * the pfn_limit (ie. not mapping the Launcher binary). */
+ /*
+ * Check that the Guest PTE flags are OK, and the page number is below
+ * the pfn_limit (ie. not mapping the Launcher binary).
+ */
check_gpte(cpu, gpte);
/* Add the _PAGE_ACCESSED and (for a write) _PAGE_DIRTY flag */
@@ -373,29 +421,40 @@
/* Get the pointer to the shadow PTE entry we're going to set. */
spte = spte_addr(cpu, *spgd, vaddr);
- /* If there was a valid shadow PTE entry here before, we release it.
- * This can happen with a write to a previously read-only entry. */
+
+ /*
+ * If there was a valid shadow PTE entry here before, we release it.
+ * This can happen with a write to a previously read-only entry.
+ */
release_pte(*spte);
- /* If this is a write, we insist that the Guest page is writable (the
- * final arg to gpte_to_spte()). */
+ /*
+ * If this is a write, we insist that the Guest page is writable (the
+ * final arg to gpte_to_spte()).
+ */
if (pte_dirty(gpte))
*spte = gpte_to_spte(cpu, gpte, 1);
else
- /* If this is a read, don't set the "writable" bit in the page
+ /*
+ * If this is a read, don't set the "writable" bit in the page
* table entry, even if the Guest says it's writable. That way
* we will come back here when a write does actually occur, so
- * we can update the Guest's _PAGE_DIRTY flag. */
+ * we can update the Guest's _PAGE_DIRTY flag.
+ */
native_set_pte(spte, gpte_to_spte(cpu, pte_wrprotect(gpte), 0));
- /* Finally, we write the Guest PTE entry back: we've set the
- * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags. */
+ /*
+ * Finally, we write the Guest PTE entry back: we've set the
+ * _PAGE_ACCESSED and maybe the _PAGE_DIRTY flags.
+ */
lgwrite(cpu, gpte_ptr, pte_t, gpte);
- /* The fault is fixed, the page table is populated, the mapping
+ /*
+ * The fault is fixed, the page table is populated, the mapping
* manipulated, the result returned and the code complete. A small
* delay and a trace of alliteration are the only indications the Guest
- * has that a page fault occurred at all. */
+ * has that a page fault occurred at all.
+ */
return true;
}
@@ -408,7 +467,8 @@
* mapped, so it's overkill.
*
* This is a quick version which answers the question: is this virtual address
- * mapped by the shadow page tables, and is it writable? */
+ * mapped by the shadow page tables, and is it writable?
+ */
static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr)
{
pgd_t *spgd;
@@ -428,16 +488,20 @@
return false;
#endif
- /* Check the flags on the pte entry itself: it must be present and
- * writable. */
+ /*
+ * Check the flags on the pte entry itself: it must be present and
+ * writable.
+ */
flags = pte_flags(*(spte_addr(cpu, *spgd, vaddr)));
return (flags & (_PAGE_PRESENT|_PAGE_RW)) == (_PAGE_PRESENT|_PAGE_RW);
}
-/* So, when pin_stack_pages() asks us to pin a page, we check if it's already
+/*
+ * So, when pin_stack_pages() asks us to pin a page, we check if it's already
* in the page tables, and if not, we call demand_page() with error code 2
- * (meaning "write"). */
+ * (meaning "write").
+ */
void pin_page(struct lg_cpu *cpu, unsigned long vaddr)
{
if (!page_writable(cpu, vaddr) && !demand_page(cpu, vaddr, 2))
@@ -485,9 +549,11 @@
/* If the entry's not present, there's nothing to release. */
if (pgd_flags(*spgd) & _PAGE_PRESENT) {
unsigned int i;
- /* Converting the pfn to find the actual PTE page is easy: turn
+ /*
+ * Converting the pfn to find the actual PTE page is easy: turn
* the page number into a physical address, then convert to a
- * virtual address (easy for kernel pages like this one). */
+ * virtual address (easy for kernel pages like this one).
+ */
pte_t *ptepage = __va(pgd_pfn(*spgd) << PAGE_SHIFT);
/* For each entry in the page, we might need to release it. */
for (i = 0; i < PTRS_PER_PTE; i++)
@@ -499,9 +565,12 @@
}
}
#endif
-/*H:445 We saw flush_user_mappings() twice: once from the flush_user_mappings()
+
+/*H:445
+ * We saw flush_user_mappings() twice: once from the flush_user_mappings()
* hypercall and once in new_pgdir() when we re-used a top-level pgdir page.
- * It simply releases every PTE page from 0 up to the Guest's kernel address. */
+ * It simply releases every PTE page from 0 up to the Guest's kernel address.
+ */
static void flush_user_mappings(struct lguest *lg, int idx)
{
unsigned int i;
@@ -510,10 +579,12 @@
release_pgd(lg->pgdirs[idx].pgdir + i);
}
-/*H:440 (v) Flushing (throwing away) page tables,
+/*H:440
+ * (v) Flushing (throwing away) page tables,
*
* The Guest has a hypercall to throw away the page tables: it's used when a
- * large number of mappings have been changed. */
+ * large number of mappings have been changed.
+ */
void guest_pagetable_flush_user(struct lg_cpu *cpu)
{
/* Drop the userspace part of the current page table. */
@@ -551,9 +622,11 @@
return pte_pfn(gpte) * PAGE_SIZE | (vaddr & ~PAGE_MASK);
}
-/* We keep several page tables. This is a simple routine to find the page
+/*
+ * We keep several page tables. This is a simple routine to find the page
* table (if any) corresponding to this top-level address the Guest has given
- * us. */
+ * us.
+ */
static unsigned int find_pgdir(struct lguest *lg, unsigned long pgtable)
{
unsigned int i;
@@ -563,9 +636,11 @@
return i;
}
-/*H:435 And this is us, creating the new page directory. If we really do
+/*H:435
+ * And this is us, creating the new page directory. If we really do
* allocate a new one (and so the kernel parts are not there), we set
- * blank_pgdir. */
+ * blank_pgdir.
+ */
static unsigned int new_pgdir(struct lg_cpu *cpu,
unsigned long gpgdir,
int *blank_pgdir)
@@ -575,8 +650,10 @@
pmd_t *pmd_table;
#endif
- /* We pick one entry at random to throw out. Choosing the Least
- * Recently Used might be better, but this is easy. */
+ /*
+ * We pick one entry at random to throw out. Choosing the Least
+ * Recently Used might be better, but this is easy.
+ */
next = random32() % ARRAY_SIZE(cpu->lg->pgdirs);
/* If it's never been allocated at all before, try now. */
if (!cpu->lg->pgdirs[next].pgdir) {
@@ -587,8 +664,10 @@
next = cpu->cpu_pgd;
else {
#ifdef CONFIG_X86_PAE
- /* In PAE mode, allocate a pmd page and populate the
- * last pgd entry. */
+ /*
+ * In PAE mode, allocate a pmd page and populate the
+ * last pgd entry.
+ */
pmd_table = (pmd_t *)get_zeroed_page(GFP_KERNEL);
if (!pmd_table) {
free_page((long)cpu->lg->pgdirs[next].pgdir);
@@ -598,8 +677,10 @@
set_pgd(cpu->lg->pgdirs[next].pgdir +
SWITCHER_PGD_INDEX,
__pgd(__pa(pmd_table) | _PAGE_PRESENT));
- /* This is a blank page, so there are no kernel
- * mappings: caller must map the stack! */
+ /*
+ * This is a blank page, so there are no kernel
+ * mappings: caller must map the stack!
+ */
*blank_pgdir = 1;
}
#else
@@ -615,19 +696,23 @@
return next;
}
-/*H:430 (iv) Switching page tables
+/*H:430
+ * (iv) Switching page tables
*
* Now we've seen all the page table setting and manipulation, let's see
* what happens when the Guest changes page tables (ie. changes the top-level
- * pgdir). This occurs on almost every context switch. */
+ * pgdir). This occurs on almost every context switch.
+ */
void guest_new_pagetable(struct lg_cpu *cpu, unsigned long pgtable)
{
int newpgdir, repin = 0;
/* Look to see if we have this one already. */
newpgdir = find_pgdir(cpu->lg, pgtable);
- /* If not, we allocate or mug an existing one: if it's a fresh one,
- * repin gets set to 1. */
+ /*
+ * If not, we allocate or mug an existing one: if it's a fresh one,
+ * repin gets set to 1.
+ */
if (newpgdir == ARRAY_SIZE(cpu->lg->pgdirs))
newpgdir = new_pgdir(cpu, pgtable, &repin);
/* Change the current pgd index to the new one. */
@@ -637,9 +722,11 @@
pin_stack_pages(cpu);
}
-/*H:470 Finally, a routine which throws away everything: all PGD entries in all
+/*H:470
+ * Finally, a routine which throws away everything: all PGD entries in all
* the shadow page tables, including the Guest's kernel mappings. This is used
- * when we destroy the Guest. */
+ * when we destroy the Guest.
+ */
static void release_all_pagetables(struct lguest *lg)
{
unsigned int i, j;
@@ -656,8 +743,10 @@
spgd = lg->pgdirs[i].pgdir + SWITCHER_PGD_INDEX;
pmdpage = __va(pgd_pfn(*spgd) << PAGE_SHIFT);
- /* And release the pmd entries of that pmd page,
- * except for the switcher pmd. */
+ /*
+ * And release the pmd entries of that pmd page,
+ * except for the switcher pmd.
+ */
for (k = 0; k < SWITCHER_PMD_INDEX; k++)
release_pmd(&pmdpage[k]);
#endif
@@ -667,10 +756,12 @@
}
}
-/* We also throw away everything when a Guest tells us it's changed a kernel
+/*
+ * We also throw away everything when a Guest tells us it's changed a kernel
* mapping. Since kernel mappings are in every page table, it's easiest to
* throw them all away. This traps the Guest in amber for a while as
- * everything faults back in, but it's rare. */
+ * everything faults back in, but it's rare.
+ */
void guest_pagetable_clear_all(struct lg_cpu *cpu)
{
release_all_pagetables(cpu->lg);
@@ -678,15 +769,19 @@
pin_stack_pages(cpu);
}
/*:*/
-/*M:009 Since we throw away all mappings when a kernel mapping changes, our
+
+/*M:009
+ * Since we throw away all mappings when a kernel mapping changes, our
* performance sucks for guests using highmem. In fact, a guest with
* PAGE_OFFSET 0xc0000000 (the default) and more than about 700MB of RAM is
* usually slower than a Guest with less memory.
*
* This, of course, cannot be fixed. It would take some kind of... well, I
- * don't know, but the term "puissant code-fu" comes to mind. :*/
+ * don't know, but the term "puissant code-fu" comes to mind.
+:*/
-/*H:420 This is the routine which actually sets the page table entry for then
+/*H:420
+ * This is the routine which actually sets the page table entry for then
* "idx"'th shadow page table.
*
* Normally, we can just throw out the old entry and replace it with 0: if they
@@ -715,31 +810,36 @@
spmd = spmd_addr(cpu, *spgd, vaddr);
if (pmd_flags(*spmd) & _PAGE_PRESENT) {
#endif
- /* Otherwise, we start by releasing
- * the existing entry. */
+ /* Otherwise, start by releasing the existing entry. */
pte_t *spte = spte_addr(cpu, *spgd, vaddr);
release_pte(*spte);
- /* If they're setting this entry as dirty or accessed,
- * we might as well put that entry they've given us
- * in now. This shaves 10% off a
- * copy-on-write micro-benchmark. */
+ /*
+ * If they're setting this entry as dirty or accessed,
+ * we might as well put that entry they've given us in
+ * now. This shaves 10% off a copy-on-write
+ * micro-benchmark.
+ */
if (pte_flags(gpte) & (_PAGE_DIRTY | _PAGE_ACCESSED)) {
check_gpte(cpu, gpte);
native_set_pte(spte,
gpte_to_spte(cpu, gpte,
pte_flags(gpte) & _PAGE_DIRTY));
- } else
- /* Otherwise kill it and we can demand_page()
- * it in later. */
+ } else {
+ /*
+ * Otherwise kill it and we can demand_page()
+ * it in later.
+ */
native_set_pte(spte, __pte(0));
+ }
#ifdef CONFIG_X86_PAE
}
#endif
}
}
-/*H:410 Updating a PTE entry is a little trickier.
+/*H:410
+ * Updating a PTE entry is a little trickier.
*
* We keep track of several different page tables (the Guest uses one for each
* process, so it makes sense to cache at least a few). Each of these have
@@ -748,12 +848,15 @@
* all the page tables, not just the current one. This is rare.
*
* The benefit is that when we have to track a new page table, we can keep all
- * the kernel mappings. This speeds up context switch immensely. */
+ * the kernel mappings. This speeds up context switch immensely.
+ */
void guest_set_pte(struct lg_cpu *cpu,
unsigned long gpgdir, unsigned long vaddr, pte_t gpte)
{
- /* Kernel mappings must be changed on all top levels. Slow, but doesn't
- * happen often. */
+ /*
+ * Kernel mappings must be changed on all top levels. Slow, but doesn't
+ * happen often.
+ */
if (vaddr >= cpu->lg->kernel_address) {
unsigned int i;
for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++)
@@ -802,12 +905,14 @@
}
#endif
-/* Once we know how much memory we have we can construct simple identity
- * (which set virtual == physical) and linear mappings
- * which will get the Guest far enough into the boot to create its own.
+/*
+ * Once we know how much memory we have we can construct simple identity (which
+ * set virtual == physical) and linear mappings which will get the Guest far
+ * enough into the boot to create its own.
*
* We lay them out of the way, just below the initrd (which is why we need to
- * know its size here). */
+ * know its size here).
+ */
static unsigned long setup_pagetables(struct lguest *lg,
unsigned long mem,
unsigned long initrd_size)
@@ -825,8 +930,10 @@
unsigned int phys_linear;
#endif
- /* We have mapped_pages frames to map, so we need
- * linear_pages page tables to map them. */
+ /*
+ * We have mapped_pages frames to map, so we need linear_pages page
+ * tables to map them.
+ */
mapped_pages = mem / PAGE_SIZE;
linear_pages = (mapped_pages + PTRS_PER_PTE - 1) / PTRS_PER_PTE;
@@ -839,8 +946,10 @@
#ifdef CONFIG_X86_PAE
pmds = (void *)linear - PAGE_SIZE;
#endif
- /* Linear mapping is easy: put every page's address into the
- * mapping in order. */
+ /*
+ * Linear mapping is easy: put every page's address into the
+ * mapping in order.
+ */
for (i = 0; i < mapped_pages; i++) {
pte_t pte;
pte = pfn_pte(i, __pgprot(_PAGE_PRESENT|_PAGE_RW|_PAGE_USER));
@@ -848,8 +957,10 @@
return -EFAULT;
}
- /* The top level points to the linear page table pages above.
- * We setup the identity and linear mappings here. */
+ /*
+ * The top level points to the linear page table pages above.
+ * We setup the identity and linear mappings here.
+ */
#ifdef CONFIG_X86_PAE
for (i = j = 0; i < mapped_pages && j < PTRS_PER_PMD;
i += PTRS_PER_PTE, j++) {
@@ -880,15 +991,19 @@
}
#endif
- /* We return the top level (guest-physical) address: remember where
- * this is. */
+ /*
+ * We return the top level (guest-physical) address: remember where
+ * this is.
+ */
return (unsigned long)pgdir - mem_base;
}
-/*H:500 (vii) Setting up the page tables initially.
+/*H:500
+ * (vii) Setting up the page tables initially.
*
* When a Guest is first created, the Launcher tells us where the toplevel of
- * its first page table is. We set some things up here: */
+ * its first page table is. We set some things up here:
+ */
int init_guest_pagetable(struct lguest *lg)
{
u64 mem;
@@ -898,14 +1013,18 @@
pgd_t *pgd;
pmd_t *pmd_table;
#endif
- /* Get the Guest memory size and the ramdisk size from the boot header
- * located at lg->mem_base (Guest address 0). */
+ /*
+ * Get the Guest memory size and the ramdisk size from the boot header
+ * located at lg->mem_base (Guest address 0).
+ */
if (copy_from_user(&mem, &boot->e820_map[0].size, sizeof(mem))
|| get_user(initrd_size, &boot->hdr.ramdisk_size))
return -EFAULT;
- /* We start on the first shadow page table, and give it a blank PGD
- * page. */
+ /*
+ * We start on the first shadow page table, and give it a blank PGD
+ * page.
+ */
lg->pgdirs[0].gpgdir = setup_pagetables(lg, mem, initrd_size);
if (IS_ERR_VALUE(lg->pgdirs[0].gpgdir))
return lg->pgdirs[0].gpgdir;
@@ -931,17 +1050,21 @@
/* We get the kernel address: above this is all kernel memory. */
if (get_user(cpu->lg->kernel_address,
&cpu->lg->lguest_data->kernel_address)
- /* We tell the Guest that it can't use the top 2 or 4 MB
- * of virtual addresses used by the Switcher. */
+ /*
+ * We tell the Guest that it can't use the top 2 or 4 MB
+ * of virtual addresses used by the Switcher.
+ */
|| put_user(RESERVE_MEM * 1024 * 1024,
&cpu->lg->lguest_data->reserve_mem)
|| put_user(cpu->lg->pgdirs[0].gpgdir,
&cpu->lg->lguest_data->pgdir))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
- /* In flush_user_mappings() we loop from 0 to
+ /*
+ * In flush_user_mappings() we loop from 0 to
* "pgd_index(lg->kernel_address)". This assumes it won't hit the
- * Switcher mappings, so check that now. */
+ * Switcher mappings, so check that now.
+ */
#ifdef CONFIG_X86_PAE
if (pgd_index(cpu->lg->kernel_address) == SWITCHER_PGD_INDEX &&
pmd_index(cpu->lg->kernel_address) == SWITCHER_PMD_INDEX)
@@ -964,12 +1087,14 @@
free_page((long)lg->pgdirs[i].pgdir);
}
-/*H:480 (vi) Mapping the Switcher when the Guest is about to run.
+/*H:480
+ * (vi) Mapping the Switcher when the Guest is about to run.
*
* The Switcher and the two pages for this CPU need to be visible in the
* Guest (and not the pages for other CPUs). We have the appropriate PTE pages
* for each CPU already set up, we just need to hook them in now we know which
- * Guest is about to run on this CPU. */
+ * Guest is about to run on this CPU.
+ */
void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages)
{
pte_t *switcher_pte_page = __get_cpu_var(switcher_pte_pages);
@@ -990,20 +1115,24 @@
#else
pgd_t switcher_pgd;
- /* Make the last PGD entry for this Guest point to the Switcher's PTE
- * page for this CPU (with appropriate flags). */
+ /*
+ * Make the last PGD entry for this Guest point to the Switcher's PTE
+ * page for this CPU (with appropriate flags).
+ */
switcher_pgd = __pgd(__pa(switcher_pte_page) | __PAGE_KERNEL_EXEC);
cpu->lg->pgdirs[cpu->cpu_pgd].pgdir[SWITCHER_PGD_INDEX] = switcher_pgd;
#endif
- /* We also change the Switcher PTE page. When we're running the Guest,
+ /*
+ * We also change the Switcher PTE page. When we're running the Guest,
* we want the Guest's "regs" page to appear where the first Switcher
* page for this CPU is. This is an optimization: when the Switcher
* saves the Guest registers, it saves them into the first page of this
* CPU's "struct lguest_pages": if we make sure the Guest's register
* page is already mapped there, we don't have to copy them out
- * again. */
+ * again.
+ */
pfn = __pa(cpu->regs_page) >> PAGE_SHIFT;
native_set_pte(®s_pte, pfn_pte(pfn, PAGE_KERNEL));
native_set_pte(&switcher_pte_page[pte_index((unsigned long)pages)],
@@ -1019,10 +1148,12 @@
free_page((long)switcher_pte_page(i));
}
-/*H:520 Setting up the Switcher PTE page for given CPU is fairly easy, given
+/*H:520
+ * Setting up the Switcher PTE page for given CPU is fairly easy, given
* the CPU number and the "struct page"s for the Switcher code itself.
*
- * Currently the Switcher is less than a page long, so "pages" is always 1. */
+ * Currently the Switcher is less than a page long, so "pages" is always 1.
+ */
static __init void populate_switcher_pte_page(unsigned int cpu,
struct page *switcher_page[],
unsigned int pages)
@@ -1043,13 +1174,16 @@
native_set_pte(&pte[i], pfn_pte(page_to_pfn(switcher_page[i]),
__pgprot(_PAGE_PRESENT|_PAGE_ACCESSED|_PAGE_RW)));
- /* The second page contains the "struct lguest_ro_state", and is
- * read-only. */
+ /*
+ * The second page contains the "struct lguest_ro_state", and is
+ * read-only.
+ */
native_set_pte(&pte[i+1], pfn_pte(page_to_pfn(switcher_page[i+1]),
__pgprot(_PAGE_PRESENT|_PAGE_ACCESSED)));
}
-/* We've made it through the page table code. Perhaps our tired brains are
+/*
+ * We've made it through the page table code. Perhaps our tired brains are
* still processing the details, or perhaps we're simply glad it's over.
*
* If nothing else, note that all this complexity in juggling shadow page tables
@@ -1058,10 +1192,13 @@
* uses exotic direct Guest pagetable manipulation, and why both Intel and AMD
* have implemented shadow page table support directly into hardware.
*
- * There is just one file remaining in the Host. */
+ * There is just one file remaining in the Host.
+ */
-/*H:510 At boot or module load time, init_pagetables() allocates and populates
- * the Switcher PTE page for each CPU. */
+/*H:510
+ * At boot or module load time, init_pagetables() allocates and populates
+ * the Switcher PTE page for each CPU.
+ */
__init int init_pagetables(struct page **switcher_page, unsigned int pages)
{
unsigned int i;