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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>
This commit is contained in:
Rusty Russell
parent
e969fed542
commit
2e04ef7691
17 changed files with 1906 additions and 1015 deletions
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@ -1,6 +1,8 @@
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/*P:400 This contains run_guest() which actually calls into the Host<->Guest
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/*P:400
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* This contains run_guest() which actually calls into the Host<->Guest
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* Switcher and analyzes the return, such as determining if the Guest wants the
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* Host to do something. This file also contains useful helper routines. :*/
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* Host to do something. This file also contains useful helper routines.
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:*/
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#include <linux/module.h>
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#include <linux/stringify.h>
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#include <linux/stddef.h>
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@ -24,7 +26,8 @@ static struct page **switcher_page;
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/* This One Big lock protects all inter-guest data structures. */
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DEFINE_MUTEX(lguest_lock);
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/*H:010 We need to set up the Switcher at a high virtual address. Remember the
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/*H:010
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* We need to set up the Switcher at a high virtual address. Remember the
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* Switcher is a few hundred bytes of assembler code which actually changes the
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* CPU to run the Guest, and then changes back to the Host when a trap or
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* interrupt happens.
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@ -33,7 +36,8 @@ DEFINE_MUTEX(lguest_lock);
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* Host since it will be running as the switchover occurs.
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*
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* Trying to map memory at a particular address is an unusual thing to do, so
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* it's not a simple one-liner. */
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* it's not a simple one-liner.
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*/
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static __init int map_switcher(void)
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{
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int i, err;
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@ -47,8 +51,10 @@ static __init int map_switcher(void)
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* easy.
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*/
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/* We allocate an array of struct page pointers. map_vm_area() wants
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* this, rather than just an array of pages. */
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/*
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* We allocate an array of struct page pointers. map_vm_area() wants
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* this, rather than just an array of pages.
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*/
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switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,
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GFP_KERNEL);
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if (!switcher_page) {
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@ -56,8 +62,10 @@ static __init int map_switcher(void)
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goto out;
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}
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/* Now we actually allocate the pages. The Guest will see these pages,
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* so we make sure they're zeroed. */
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/*
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* Now we actually allocate the pages. The Guest will see these pages,
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* so we make sure they're zeroed.
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*/
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for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) {
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unsigned long addr = get_zeroed_page(GFP_KERNEL);
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if (!addr) {
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@ -67,19 +75,23 @@ static __init int map_switcher(void)
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switcher_page[i] = virt_to_page(addr);
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}
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/* First we check that the Switcher won't overlap the fixmap area at
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/*
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* First we check that the Switcher won't overlap the fixmap area at
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* the top of memory. It's currently nowhere near, but it could have
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* very strange effects if it ever happened. */
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* very strange effects if it ever happened.
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*/
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if (SWITCHER_ADDR + (TOTAL_SWITCHER_PAGES+1)*PAGE_SIZE > FIXADDR_START){
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err = -ENOMEM;
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printk("lguest: mapping switcher would thwack fixmap\n");
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goto free_pages;
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}
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/* Now we reserve the "virtual memory area" we want: 0xFFC00000
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/*
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* Now we reserve the "virtual memory area" we want: 0xFFC00000
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* (SWITCHER_ADDR). We might not get it in theory, but in practice
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* it's worked so far. The end address needs +1 because __get_vm_area
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* allocates an extra guard page, so we need space for that. */
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* allocates an extra guard page, so we need space for that.
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*/
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switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE,
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VM_ALLOC, SWITCHER_ADDR, SWITCHER_ADDR
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+ (TOTAL_SWITCHER_PAGES+1) * PAGE_SIZE);
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@ -89,11 +101,13 @@ static __init int map_switcher(void)
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goto free_pages;
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}
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/* This code actually sets up the pages we've allocated to appear at
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/*
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* This code actually sets up the pages we've allocated to appear at
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* SWITCHER_ADDR. map_vm_area() takes the vma we allocated above, the
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* kind of pages we're mapping (kernel pages), and a pointer to our
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* array of struct pages. It increments that pointer, but we don't
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* care. */
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* care.
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*/
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pagep = switcher_page;
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err = map_vm_area(switcher_vma, PAGE_KERNEL_EXEC, &pagep);
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if (err) {
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@ -101,8 +115,10 @@ static __init int map_switcher(void)
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goto free_vma;
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}
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/* Now the Switcher is mapped at the right address, we can't fail!
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* Copy in the compiled-in Switcher code (from <arch>_switcher.S). */
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/*
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* Now the Switcher is mapped at the right address, we can't fail!
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* Copy in the compiled-in Switcher code (from <arch>_switcher.S).
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*/
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memcpy(switcher_vma->addr, start_switcher_text,
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end_switcher_text - start_switcher_text);
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@ -124,8 +140,7 @@ out:
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}
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/*:*/
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/* Cleaning up the mapping when the module is unloaded is almost...
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* too easy. */
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/* Cleaning up the mapping when the module is unloaded is almost... too easy. */
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static void unmap_switcher(void)
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{
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unsigned int i;
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@ -151,16 +166,19 @@ static void unmap_switcher(void)
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* But we can't trust the Guest: it might be trying to access the Launcher
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* code. We have to check that the range is below the pfn_limit the Launcher
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* gave us. We have to make sure that addr + len doesn't give us a false
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* positive by overflowing, too. */
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* positive by overflowing, too.
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*/
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bool lguest_address_ok(const struct lguest *lg,
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unsigned long addr, unsigned long len)
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{
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return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
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}
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/* This routine copies memory from the Guest. Here we can see how useful the
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/*
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* This routine copies memory from the Guest. Here we can see how useful the
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* kill_lguest() routine we met in the Launcher can be: we return a random
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* value (all zeroes) instead of needing to return an error. */
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* value (all zeroes) instead of needing to return an error.
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*/
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void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes)
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{
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if (!lguest_address_ok(cpu->lg, addr, bytes)
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@ -181,9 +199,11 @@ void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b,
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}
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/*:*/
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/*H:030 Let's jump straight to the the main loop which runs the Guest.
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/*H:030
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* Let's jump straight to the the main loop which runs the Guest.
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* Remember, this is called by the Launcher reading /dev/lguest, and we keep
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* going around and around until something interesting happens. */
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* going around and around until something interesting happens.
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*/
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int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
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{
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/* We stop running once the Guest is dead. */
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@ -195,8 +215,10 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
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if (cpu->hcall)
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do_hypercalls(cpu);
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/* It's possible the Guest did a NOTIFY hypercall to the
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* Launcher, in which case we return from the read() now. */
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/*
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* It's possible the Guest did a NOTIFY hypercall to the
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* Launcher, in which case we return from the read() now.
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*/
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if (cpu->pending_notify) {
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if (!send_notify_to_eventfd(cpu)) {
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if (put_user(cpu->pending_notify, user))
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@ -209,29 +231,39 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
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if (signal_pending(current))
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return -ERESTARTSYS;
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/* Check if there are any interrupts which can be delivered now:
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/*
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* Check if there are any interrupts which can be delivered now:
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* if so, this sets up the hander to be executed when we next
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* run the Guest. */
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* run the Guest.
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*/
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irq = interrupt_pending(cpu, &more);
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if (irq < LGUEST_IRQS)
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try_deliver_interrupt(cpu, irq, more);
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/* All long-lived kernel loops need to check with this horrible
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/*
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* All long-lived kernel loops need to check with this horrible
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* thing called the freezer. If the Host is trying to suspend,
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* it stops us. */
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* it stops us.
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*/
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try_to_freeze();
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/* Just make absolutely sure the Guest is still alive. One of
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* those hypercalls could have been fatal, for example. */
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/*
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* Just make absolutely sure the Guest is still alive. One of
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* those hypercalls could have been fatal, for example.
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*/
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if (cpu->lg->dead)
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break;
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/* If the Guest asked to be stopped, we sleep. The Guest's
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* clock timer will wake us. */
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/*
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* If the Guest asked to be stopped, we sleep. The Guest's
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* clock timer will wake us.
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*/
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if (cpu->halted) {
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set_current_state(TASK_INTERRUPTIBLE);
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/* Just before we sleep, make sure no interrupt snuck in
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* which we should be doing. */
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/*
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* Just before we sleep, make sure no interrupt snuck in
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* which we should be doing.
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*/
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if (interrupt_pending(cpu, &more) < LGUEST_IRQS)
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set_current_state(TASK_RUNNING);
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else
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continue;
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}
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/* OK, now we're ready to jump into the Guest. First we put up
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* the "Do Not Disturb" sign: */
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/*
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* OK, now we're ready to jump into the Guest. First we put up
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* the "Do Not Disturb" sign:
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*/
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local_irq_disable();
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/* Actually run the Guest until something happens. */
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@ -327,8 +361,10 @@ static void __exit fini(void)
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}
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/*:*/
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/* The Host side of lguest can be a module. This is a nice way for people to
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* play with it. */
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/*
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* The Host side of lguest can be a module. This is a nice way for people to
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* play with it.
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*/
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module_init(init);
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module_exit(fini);
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MODULE_LICENSE("GPL");
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