* When lazy_mode is set, it means we're allowed to defer all hypercalls and do
* them as a batch when lazy_mode is eventually turned off. Because hypercalls
* are reasonably expensive, batching them up makes sense. For example, a
- * large mmap might update dozens of page table entries: that code calls
+ * large munmap might update dozens of page table entries: that code calls
* paravirt_enter_lazy_mmu(), does the dozen updates, then calls
* lguest_leave_lazy_mode().
*
/*:*/
/*G:033
- * Here are our first native-instruction replacements: four functions for
- * interrupt control.
+ * After that diversion we return to our first native-instruction
+ * replacements: four functions for interrupt control.
*
* The simplest way of implementing these would be to have "turn interrupts
* off" and "turn interrupts on" hypercalls. Unfortunately, this is too slow:
return lguest_data.irq_enabled;
}
-/* "restore_flags" just sets the flags back to the value given. */
+/* restore_flags() just sets the flags back to the value given. */
static void restore_fl(unsigned long flags)
{
lguest_data.irq_enabled = flags;
* it. The Host needs to know when the Guest wants to change them, so we have
* a whole series of functions like read_cr0() and write_cr0().
*
- * We start with CR0. CR0 allows you to turn on and off all kinds of basic
+ * We start with cr0. cr0 allows you to turn on and off all kinds of basic
* features, but Linux only really cares about one: the horrifically-named Task
* Switched (TS) bit at bit 3 (ie. 8)
*
current_cr0 &= ~X86_CR0_TS;
}
-/* CR2 is the virtual address of the last page fault, which the Guest only ever
+/* cr2 is the virtual address of the last page fault, which the Guest only ever
* reads. The Host kindly writes this into our "struct lguest_data", so we
* just read it out of there. */
static unsigned long lguest_read_cr2(void)
return lguest_data.cr2;
}
-/* CR3 is the current toplevel pagetable page: the principle is the same as
+/* cr3 is the current toplevel pagetable page: the principle is the same as
* cr0. Keep a local copy, and tell the Host when it changes. */
static void lguest_write_cr3(unsigned long cr3)
{
return current_cr3;
}
-/* CR4 is used to enable and disable PGE, but we don't care. */
+/* cr4 is used to enable and disable PGE, but we don't care. */
static unsigned long lguest_read_cr4(void)
{
return 0;
* maps virtual addresses to physical addresses using "page tables". We could
* use one huge index of 1 million entries: each address is 4 bytes, so that's
* 1024 pages just to hold the page tables. But since most virtual addresses
- * are unused, we use a two level index which saves space. The CR3 register
+ * are unused, we use a two level index which saves space. The cr3 register
* contains the physical address of the top level "page directory" page, which
* contains physical addresses of up to 1024 second-level pages. Each of these
* second level pages contains up to 1024 physical addresses of actual pages,
*
* Here's a diagram, where arrows indicate physical addresses:
*
- * CR3 ---> +---------+
+ * cr3 ---> +---------+
* | --------->+---------+
* | | | PADDR1 |
* Top-level | | PADDR2 |
*
* ... except in early boot when the kernel sets up the initial pagetables,
* which makes booting astonishingly slow. So we don't even tell the Host
- * anything changed until we've done the first page table switch.
- */
+ * anything changed until we've done the first page table switch. */
static void lguest_set_pte(pte_t *ptep, pte_t pteval)
{
*ptep = pteval;
/* Set up the timer interrupt (0) to go to our simple timer routine */
set_irq_handler(0, lguest_time_irq);
- /* Our clock structure look like arch/i386/kernel/tsc.c if we can use
- * the TSC, otherwise it's a dumb nanosecond-resolution clock. Either
- * way, the "rating" is initialized so high that it's always chosen
- * over any other clocksource. */
+ /* Our clock structure looks like arch/x86/kernel/tsc_32.c if we can
+ * use the TSC, otherwise it's a dumb nanosecond-resolution clock.
+ * Either way, the "rating" is set so high that it's always chosen over
+ * any other clocksource. */
if (lguest_data.tsc_khz)
lguest_clock.mult = clocksource_khz2mult(lguest_data.tsc_khz,
lguest_clock.shift);
* to work. They're pretty simple.
*/
-/* The Guest needs to tell the host what stack it expects traps to use. For
+/* The Guest needs to tell the Host what stack it expects traps to use. For
* native hardware, this is part of the Task State Segment mentioned above in
* lguest_load_tr_desc(), but to help hypervisors there's this special call.
*
return "LGUEST";
}
-/* Before virtqueues are set up, we use LHCALL_NOTIFY on normal memory to
- * produce console output. */
+/* We will eventually use the virtio console device to produce console output,
+ * but before that is set up we use LHCALL_NOTIFY on normal memory to produce
+ * console output. */
static __init int early_put_chars(u32 vtermno, const char *buf, int count)
{
char scratch[17];
unsigned int len = count;
+ /* We use a nul-terminated string, so we have to make a copy. Icky,
+ * huh? */
if (len > sizeof(scratch) - 1)
len = sizeof(scratch) - 1;
scratch[len] = '\0';
* Our current solution is to allow the paravirt back end to optionally patch
* over the indirect calls to replace them with something more efficient. We
* patch the four most commonly called functions: disable interrupts, enable
- * interrupts, restore interrupts and save interrupts. We usually have 10
+ * interrupts, restore interrupts and save interrupts. We usually have 6 or 10
* bytes to patch into: the Guest versions of these operations are small enough
* that we can fit comfortably.
*
asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");
/* The Host uses the top of the Guest's virtual address space for the
- * Host<->Guest Switcher, and it tells us how much it needs in
+ * Host<->Guest Switcher, and it tells us how big that is in
* lguest_data.reserve_mem, set up on the LGUEST_INIT hypercall. */
reserve_top_address(lguest_data.reserve_mem);
/*
* This marks the end of stage II of our journey, The Guest.
*
- * It is now time for us to explore the nooks and crannies of the three Guest
- * devices and complete our understanding of the Guest in "make Drivers".
+ * It is now time for us to explore the layer of virtual drivers and complete
+ * our understanding of the Guest in "make Drivers".
*/
projects / deliverable / linux.git / blobdiff