/*P:400 This contains run_guest() which actually calls into the Host<->Guest * Switcher and analyzes the return, such as determining if the Guest wants the * Host to do something. This file also contains useful helper routines, and a * couple of non-obvious setup and teardown pieces which were implemented after * days of debugging pain. :*/ #include <linux/module.h> #include <linux/stringify.h> #include <linux/stddef.h> #include <linux/io.h> #include <linux/mm.h> #include <linux/vmalloc.h> #include <linux/cpu.h> #include <linux/freezer.h> #include <asm/paravirt.h> #include <asm/desc.h> #include <asm/pgtable.h> #include <asm/uaccess.h> #include <asm/poll.h> #include <asm/highmem.h> #include <asm/asm-offsets.h> #include <asm/i387.h> #include "lg.h" /* Found in switcher.S */ extern char start_switcher_text[], end_switcher_text[], switch_to_guest[]; extern unsigned long default_idt_entries[]; /* Every guest maps the core switcher code. */ #define SHARED_SWITCHER_PAGES \ DIV_ROUND_UP(end_switcher_text - start_switcher_text, PAGE_SIZE) /* Pages for switcher itself, then two pages per cpu */ #define TOTAL_SWITCHER_PAGES (SHARED_SWITCHER_PAGES + 2 * NR_CPUS) /* We map at -4M for ease of mapping into the guest (one PTE page). */ #define SWITCHER_ADDR 0xFFC00000 static struct vm_struct *switcher_vma; static struct page **switcher_page; static int cpu_had_pge; static struct { unsigned long offset; unsigned short segment; } lguest_entry; /* This One Big lock protects all inter-guest data structures. */ DEFINE_MUTEX(lguest_lock); static DEFINE_PER_CPU(struct lguest *, last_guest); /* FIXME: Make dynamic. */ #define MAX_LGUEST_GUESTS 16 struct lguest lguests[MAX_LGUEST_GUESTS]; /* Offset from where switcher.S was compiled to where we've copied it */ static unsigned long switcher_offset(void) { return SWITCHER_ADDR - (unsigned long)start_switcher_text; } /* This cpu's struct lguest_pages. */ static struct lguest_pages *lguest_pages(unsigned int cpu) { return &(((struct lguest_pages *) (SWITCHER_ADDR + SHARED_SWITCHER_PAGES*PAGE_SIZE))[cpu]); } /*H:010 We need to set up the Switcher at a high virtual address. Remember the * Switcher is a few hundred bytes of assembler code which actually changes the * CPU to run the Guest, and then changes back to the Host when a trap or * interrupt happens. * * The Switcher code must be at the same virtual address in the Guest as the * Host since it will be running as the switchover occurs. * * Trying to map memory at a particular address is an unusual thing to do, so * it's not a simple one-liner. We also set up the per-cpu parts of the * Switcher here. */ static __init int map_switcher(void) { int i, err; struct page **pagep; /* * Map the Switcher in to high memory. * * It turns out that if we choose the address 0xFFC00000 (4MB under the * top virtual address), it makes setting up the page tables really * easy. */ /* We allocate an array of "struct page"s. map_vm_area() wants the * pages in this form, rather than just an array of pointers. */ switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES, GFP_KERNEL); if (!switcher_page) { err = -ENOMEM; goto out; } /* Now we actually allocate the pages. The Guest will see these pages, * so we make sure they're zeroed. */ for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) { unsigned long addr = get_zeroed_page(GFP_KERNEL); if (!addr) { err = -ENOMEM; goto free_some_pages; } switcher_page[i] = virt_to_page(addr); } /* Now we reserve the "virtual memory area" we want: 0xFFC00000 * (SWITCHER_ADDR). We might not get it in theory, but in practice * it's worked so far. */ switcher_vma = __get_vm_area(TOTAL_SWITCHER_PAGES * PAGE_SIZE, VM_ALLOC, SWITCHER_ADDR, VMALLOC_END); if (!switcher_vma) { err = -ENOMEM; printk("lguest: could not map switcher pages high\n"); goto free_pages; } /* This code actually sets up the pages we've allocated to appear at * SWITCHER_ADDR. map_vm_area() takes the vma we allocated above, the * kind of pages we're mapping (kernel pages), and a pointer to our * array of struct pages. It increments that pointer, but we don't * care. */ pagep = switcher_page; err = map_vm_area(switcher_vma, PAGE_KERNEL, &pagep); if (err) { printk("lguest: map_vm_area failed: %i\n", err); goto free_vma; } /* Now the switcher is mapped at the right address, we can't fail! * Copy in the compiled-in Switcher code (from switcher.S). */ memcpy(switcher_vma->addr, start_switcher_text, end_switcher_text - start_switcher_text); /* Most of the switcher.S doesn't care that it's been moved; on Intel, * jumps are relative, and it doesn't access any references to external * code or data. * * 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. */ for (i = 0; i < IDT_ENTRIES; i++) default_idt_entries[i] += switcher_offset(); /* * Set up the Switcher's per-cpu areas. * * Each CPU gets two pages of its own within the high-mapped region * (aka. "struct lguest_pages"). Much of this can be initialized now, * but some depends on what Guest we are running (which is set up in * copy_in_guest_info()). */ for_each_possible_cpu(i) { /* lguest_pages() returns this CPU's two pages. */ struct lguest_pages *pages = lguest_pages(i); /* This is a convenience pointer to make the code fit one * statement to a line. */ struct lguest_ro_state *state = &pages->state; /* The Global Descriptor Table: the Host has a different one * for each CPU. We keep a descriptor for the GDT which says * where it is and how big it is (the size is actually the last * byte, not the size, hence the "-1"). */ state->host_gdt_desc.size = GDT_SIZE-1; state->host_gdt_desc.address = (long)get_cpu_gdt_table(i); /* All CPUs on the Host use the same Interrupt Descriptor * Table, so we just use store_idt(), which gets this CPU's IDT * descriptor. */ store_idt(&state->host_idt_desc); /* The descriptors for the Guest's GDT and IDT can be filled * out now, too. We copy the GDT & IDT into ->guest_gdt and * ->guest_idt before actually running the Guest. */ state->guest_idt_desc.size = sizeof(state->guest_idt)-1; state->guest_idt_desc.address = (long)&state->guest_idt; state->guest_gdt_desc.size = sizeof(state->guest_gdt)-1; 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 * we start it at the end of that structure. */ state->guest_tss.esp0 = (long)(&pages->regs + 1); /* And this is the GDT entry to use for the stack: we keep a * couple of special LGUEST entries. */ state->guest_tss.ss0 = LGUEST_DS; /* x86 can have a finegrained bitmap which indicates what I/O * ports the process can use. We set it to the end of our * structure, meaning "none". */ state->guest_tss.io_bitmap_base = sizeof(state->guest_tss); /* Some GDT entries are the same across all Guests, so we can * set them up now. */ setup_default_gdt_entries(state); /* Most IDT entries are the same for all Guests, too.*/ setup_default_idt_entries(state, default_idt_entries); /* The Host needs to be able to use the LGUEST segments on this * CPU, too, so put them in the Host GDT. */ get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT; get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT; } /* In the Switcher, we want the %cs segment register to use the * LGUEST_CS GDT entry: we've put that in the Host and Guest GDTs, so * it will be undisturbed when we switch. To change %cs and jump we * need this structure to feed to Intel's "lcall" instruction. */ lguest_entry.offset = (long)switch_to_guest + switcher_offset(); lguest_entry.segment = LGUEST_CS; printk(KERN_INFO "lguest: mapped switcher at %p\n", switcher_vma->addr); /* And we succeeded... */ return 0; free_vma: vunmap(switcher_vma->addr); free_pages: i = TOTAL_SWITCHER_PAGES; free_some_pages: for (--i; i >= 0; i--) __free_pages(switcher_page[i], 0); kfree(switcher_page); out: return err; } /*:*/ /* Cleaning up the mapping when the module is unloaded is almost... * too easy. */ static void unmap_switcher(void) { unsigned int i; /* vunmap() undoes *both* map_vm_area() and __get_vm_area(). */ vunmap(switcher_vma->addr); /* Now we just need to free the pages we copied the switcher into */ for (i = 0; i < TOTAL_SWITCHER_PAGES; i++) __free_pages(switcher_page[i], 0); } /*H:130 Our Guest is usually so well behaved; it never tries to do things it * isn't allowed to. Unfortunately, "struct paravirt_ops" isn't quite * complete, because it doesn't contain replacements for the Intel I/O * instructions. As a result, the Guest sometimes fumbles across one during * the boot process as it probes for various things which are usually attached * to a PC. * * When the Guest uses one of these instructions, we get trap #13 (General * Protection Fault) and come here. We see if it's one of those troublesome * instructions and skip over it. We return true if we did. */ static int emulate_insn(struct lguest *lg) { u8 insn; unsigned int insnlen = 0, in = 0, shift = 0; /* The eip contains the *virtual* address of the Guest's instruction: * guest_pa just subtracts the Guest's page_offset. */ unsigned long physaddr = guest_pa(lg, lg->regs->eip); /* The guest_pa() function only works for Guest kernel addresses, but * that's all we're trying to do anyway. */ if (lg->regs->eip < lg->page_offset) return 0; /* Decoding x86 instructions is icky. */ lgread(lg, &insn, physaddr, 1); /* 0x66 is an "operand prefix". It means it's using the upper 16 bits of the eax register. */ if (insn == 0x66) { shift = 16; /* The instruction is 1 byte so far, read the next byte. */ insnlen = 1; lgread(lg, &insn, physaddr + insnlen, 1); } /* We can ignore the lower bit for the moment and decode the 4 opcodes * we need to emulate. */ switch (insn & 0xFE) { case 0xE4: /* in <next byte>,%al */ insnlen += 2; in = 1; break; case 0xEC: /* in (%dx),%al */ insnlen += 1; in = 1; break; case 0xE6: /* out %al,<next byte> */ insnlen += 2; break; case 0xEE: /* out %al,(%dx) */ insnlen += 1; break; default: /* OK, we don't know what this is, can't emulate. */ return 0; } /* If it was an "IN" instruction, they expect the result to be read * into %eax, so we change %eax. We always return all-ones, which * traditionally means "there's nothing there". */ if (in) { /* Lower bit tells is whether it's a 16 or 32 bit access */ if (insn & 0x1) lg->regs->eax = 0xFFFFFFFF; else lg->regs->eax |= (0xFFFF << shift); } /* Finally, we've "done" the instruction, so move past it. */ lg->regs->eip += insnlen; /* Success! */ return 1; } /*:*/ /*L:305 * Dealing With Guest Memory. * * When the Guest gives us (what it thinks is) a physical address, we can use * the normal copy_from_user() & copy_to_user() on that address: remember, * Guest physical == Launcher virtual. * * But we can't trust the Guest: it might be trying to access the Launcher * code. We have to check that the range is below the pfn_limit the Launcher * gave us. We have to make sure that addr + len doesn't give us a false * positive by overflowing, too. */ int lguest_address_ok(const struct lguest *lg, unsigned long addr, unsigned long len) { return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr); } /* This is a convenient routine to get a 32-bit value from the Guest (a very * common operation). Here we can see how useful the kill_lguest() routine we * met in the Launcher can be: we return a random value (0) instead of needing * to return an error. */ u32 lgread_u32(struct lguest *lg, unsigned long addr) { u32 val = 0; /* Don't let them access lguest binary. */ if (!lguest_address_ok(lg, addr, sizeof(val)) || get_user(val, (u32 __user *)addr) != 0) kill_guest(lg, "bad read address %#lx", addr); return val; } /* Same thing for writing a value. */ void lgwrite_u32(struct lguest *lg, unsigned long addr, u32 val) { if (!lguest_address_ok(lg, addr, sizeof(val)) || put_user(val, (u32 __user *)addr) != 0) kill_guest(lg, "bad write address %#lx", addr); } /* This routine is more generic, and copies a range of Guest bytes into a * buffer. If the copy_from_user() fails, we fill the buffer with zeroes, so * the caller doesn't end up using uninitialized kernel memory. */ void lgread(struct lguest *lg, void *b, unsigned long addr, unsigned bytes) { if (!lguest_address_ok(lg, addr, bytes) || copy_from_user(b, (void __user *)addr, bytes) != 0) { /* copy_from_user should do this, but as we rely on it... */ memset(b, 0, bytes); kill_guest(lg, "bad read address %#lx len %u", addr, bytes); } } /* Similarly, our generic routine to copy into a range of Guest bytes. */ void lgwrite(struct lguest *lg, unsigned long addr, const void *b, unsigned bytes) { if (!lguest_address_ok(lg, addr, bytes) || copy_to_user((void __user *)addr, b, bytes) != 0) kill_guest(lg, "bad write address %#lx len %u", addr, bytes); } /* (end of memory access helper routines) :*/ static void set_ts(void) { u32 cr0; cr0 = read_cr0(); if (!(cr0 & 8)) write_cr0(cr0|8); } /*S:010 * We are getting close to the Switcher. * * Remember that each CPU has two pages which are visible to the Guest when it * runs on that CPU. This has to contain the state for that Guest: we copy the * state in just before we run the Guest. * * Each Guest has "changed" flags which indicate what has changed in the Guest * since it last ran. We saw this set in interrupts_and_traps.c and * segments.c. */ static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages) { /* Copying all this data can be quite expensive. We usually run the * same Guest we ran last time (and that Guest hasn't run anywhere else * meanwhile). If that's not the case, we pretend everything in the * Guest has changed. */ if (__get_cpu_var(last_guest) != lg || lg->last_pages != pages) { __get_cpu_var(last_guest) = lg; lg->last_pages = pages; lg->changed = CHANGED_ALL; } /* These copies are pretty cheap, so we do them unconditionally: */ /* Save the current Host top-level page directory. */ pages->state.host_cr3 = __pa(current->mm->pgd); /* Set up the Guest's page tables to see this CPU's pages (and no * other CPU's pages). */ map_switcher_in_guest(lg, pages); /* Set up the two "TSS" members which tell the CPU what stack to use * for traps which do directly into the Guest (ie. traps at privilege * level 1). */ pages->state.guest_tss.esp1 = lg->esp1; pages->state.guest_tss.ss1 = lg->ss1; /* Copy direct-to-Guest trap entries. */ if (lg->changed & CHANGED_IDT) copy_traps(lg, pages->state.guest_idt, default_idt_entries); /* Copy all GDT entries which the Guest can change. */ if (lg->changed & CHANGED_GDT) copy_gdt(lg, pages->state.guest_gdt); /* If only the TLS entries have changed, copy them. */ else if (lg->changed & CHANGED_GDT_TLS) copy_gdt_tls(lg, pages->state.guest_gdt); /* Mark the Guest as unchanged for next time. */ lg->changed = 0; } /* Finally: the code to actually call into the Switcher to run the Guest. */ static void run_guest_once(struct lguest *lg, struct lguest_pages *pages) { /* This is a dummy value we need for GCC's sake. */ unsigned int clobber; /* Copy the guest-specific information into this CPU's "struct * lguest_pages". */ copy_in_guest_info(lg, pages); /* Set the trap number to 256 (impossible value). If we fault while * switching to the Guest (bad segment registers or bug), this will * cause us to abort the Guest. */ lg->regs->trapnum = 256; /* Now: we push the "eflags" register on the stack, then do an "lcall". * This is how we change from using the kernel code segment to using * the dedicated lguest code segment, as well as jumping into the * Switcher. * * The lcall also pushes the old code segment (KERNEL_CS) onto the * stack, then the address of this call. This stack layout happens to * exactly match the stack of an interrupt... */ asm volatile("pushf; lcall *lguest_entry" /* This is how we tell GCC that %eax ("a") and %ebx ("b") * are changed by this routine. The "=" means output. */ : "=a"(clobber), "=b"(clobber) /* %eax contains the pages pointer. ("0" refers to the * 0-th argument above, ie "a"). %ebx contains the * physical address of the Guest's top-level page * directory. */ : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir)) /* We tell gcc that all these registers could change, * which means we don't have to save and restore them in * the Switcher. */ : "memory", "%edx", "%ecx", "%edi", "%esi"); } /*:*/ /*H:030 Let's jump straight to the the main loop which runs the Guest. * Remember, this is called by the Launcher reading /dev/lguest, and we keep * going around and around until something interesting happens. */ int run_guest(struct lguest *lg, unsigned long __user *user) { /* We stop running once the Guest is dead. */ while (!lg->dead) { /* We need to initialize this, otherwise gcc complains. It's * not (yet) clever enough to see that it's initialized when we * need it. */ unsigned int cr2 = 0; /* Damn gcc */ /* First we run any hypercalls the Guest wants done: either in * the hypercall ring in "struct lguest_data", or directly by * using int 31 (LGUEST_TRAP_ENTRY). */ do_hypercalls(lg); /* It's possible the Guest did a SEND_DMA hypercall to the * Launcher, in which case we return from the read() now. */ if (lg->dma_is_pending) { if (put_user(lg->pending_dma, user) || put_user(lg->pending_key, user+1)) return -EFAULT; return sizeof(unsigned long)*2; } /* Check for signals */ if (signal_pending(current)) return -ERESTARTSYS; /* If Waker set break_out, return to Launcher. */ if (lg->break_out) return -EAGAIN; /* Check if there are any interrupts which can be delivered * now: if so, this sets up the hander to be executed when we * next run the Guest. */ maybe_do_interrupt(lg); /* All long-lived kernel loops need to check with this horrible * thing called the freezer. If the Host is trying to suspend, * it stops us. */ try_to_freeze(); /* Just make absolutely sure the Guest is still alive. One of * those hypercalls could have been fatal, for example. */ if (lg->dead) break; /* If the Guest asked to be stopped, we sleep. The Guest's * clock timer or LHCALL_BREAK from the Waker will wake us. */ if (lg->halted) { set_current_state(TASK_INTERRUPTIBLE); schedule(); continue; } /* OK, now we're ready to jump into the Guest. First we put up * the "Do Not Disturb" sign: */ local_irq_disable(); /* Remember the awfully-named TS bit? If the Guest has asked * to set it we set it now, so we can trap and pass that trap * to the Guest if it uses the FPU. */ if (lg->ts) set_ts(); /* SYSENTER is an optimized way of doing system calls. We * can't allow it because it always jumps to privilege level 0. * A normal Guest won't try it because we don't advertise it in * CPUID, but a malicious Guest (or malicious Guest userspace * program) could, so we tell the CPU to disable it before * running the Guest. */ if (boot_cpu_has(X86_FEATURE_SEP)) wrmsr(MSR_IA32_SYSENTER_CS, 0, 0); /* Now we actually run the Guest. It will pop back out when * something interesting happens, and we can examine its * registers to see what it was doing. */ run_guest_once(lg, lguest_pages(raw_smp_processor_id())); /* The "regs" pointer 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. */ /* If the Guest page faulted, then the cr2 register will tell * us the bad virtual address. We have to grab this now, * because once we re-enable interrupts an interrupt could * fault and thus overwrite cr2, or we could even move off to a * different CPU. */ if (lg->regs->trapnum == 14) cr2 = read_cr2(); /* Similarly, if we took a trap because the Guest used the FPU, * we have to restore the FPU it expects to see. */ else if (lg->regs->trapnum == 7) math_state_restore(); /* Restore SYSENTER if it's supposed to be on. */ if (boot_cpu_has(X86_FEATURE_SEP)) wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); /* Now we're ready to be interrupted or moved to other CPUs */ local_irq_enable(); /* OK, so what happened? */ switch (lg->regs->trapnum) { case 13: /* We've intercepted a GPF. */ /* Check if this was one of those annoying IN or OUT * instructions which we need to emulate. If so, we * just go back into the Guest after we've done it. */ if (lg->regs->errcode == 0) { if (emulate_insn(lg)) continue; } 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. * * The errcode tells whether this was a read or a * write, and whether kernel or userspace code. */ if (demand_page(lg, cr2, lg->regs->errcode)) continue; /* OK, it's really not there (or not OK): the Guest * needs to know. We write out the cr2 value so it * knows where the fault occurred. * * Note that if the Guest were really messed up, this * could happen before it's done the INITIALIZE * hypercall, so lg->lguest_data will be NULL, so * &lg->lguest_data->cr2 will be address 8. Writing * into that address won't hurt the Host at all, * though. */ if (put_user(cr2, &lg->lguest_data->cr2)) kill_guest(lg, "Writing cr2"); break; case 7: /* We've intercepted a Device Not Available fault. */ /* If the Guest doesn't want to know, we already * restored the Floating Point Unit, so we just * continue without telling it. */ if (!lg->ts) continue; break; case 32 ... 255: /* These values mean a real interrupt occurred, in * which case the Host handler has already been run. * We just do a friendly check if another process * should now be run, then fall through to loop * around: */ cond_resched(); case LGUEST_TRAP_ENTRY: /* Handled at top of loop */ continue; } /* If we get here, it's a trap the Guest wants to know * about. */ if (deliver_trap(lg, lg->regs->trapnum)) continue; /* 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. */ kill_guest(lg, "unhandled trap %li at %#lx (%#lx)", lg->regs->trapnum, lg->regs->eip, lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode); } /* The Guest is dead => "No such file or directory" */ return -ENOENT; } /* Now we can look at each of the routines this calls, in increasing order of * complexity: do_hypercalls(), emulate_insn(), maybe_do_interrupt(), * deliver_trap() and demand_page(). After all those, we'll be ready to * examine the Switcher, and our philosophical understanding of the Host/Guest * duality will be complete. :*/ int find_free_guest(void) { unsigned int i; for (i = 0; i < MAX_LGUEST_GUESTS; i++) if (!lguests[i].tsk) return i; return -1; } static void adjust_pge(void *on) { if (on) write_cr4(read_cr4() | X86_CR4_PGE); else write_cr4(read_cr4() & ~X86_CR4_PGE); } /*H:000 * Welcome to the Host! * * By this point your brain has been tickled by the Guest code and numbed by * the Launcher code; prepare for it to be stretched by the Host code. This is * the heart. Let's begin at the initialization routine for the Host's lg * module. */ static int __init init(void) { int err; /* Lguest can't run under Xen, VMI or itself. It does Tricky Stuff. */ if (paravirt_enabled()) { printk("lguest is afraid of %s\n", paravirt_ops.name); return -EPERM; } /* First we put the Switcher up in very high virtual memory. */ err = map_switcher(); if (err) return err; /* Now we set up the pagetable implementation for the Guests. */ err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES); if (err) { unmap_switcher(); return err; } /* The I/O subsystem needs some things initialized. */ lguest_io_init(); /* /dev/lguest needs to be registered. */ err = lguest_device_init(); if (err) { free_pagetables(); unmap_switcher(); return err; } /* Finally, we need to turn off "Page Global Enable". PGE is an * optimization where page table entries are specially marked to show * they never change. The Host kernel marks all the kernel pages this * way because it's always present, even when userspace is running. * * Lguest breaks this: unbeknownst to the rest of the Host kernel, we * switch to the Guest kernel. If you don't disable this on all CPUs, * you'll get really weird bugs that you'll chase for two days. * * I used to turn PGE off every time we switched to the Guest and back * on when we return, but that slowed the Switcher down noticibly. */ /* We don't need the complexity of CPUs coming and going while we're * doing this. */ lock_cpu_hotplug(); if (cpu_has_pge) { /* We have a broader idea of "global". */ /* Remember that this was originally set (for cleanup). */ cpu_had_pge = 1; /* adjust_pge is a helper function which sets or unsets the PGE * bit on its CPU, depending on the argument (0 == unset). */ on_each_cpu(adjust_pge, (void *)0, 0, 1); /* Turn off the feature in the global feature set. */ clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); } unlock_cpu_hotplug(); /* All good! */ return 0; } /* Cleaning up is just the same code, backwards. With a little French. */ static void __exit fini(void) { lguest_device_remove(); free_pagetables(); unmap_switcher(); /* If we had PGE before we started, turn it back on now. */ lock_cpu_hotplug(); if (cpu_had_pge) { set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability); /* adjust_pge's argument "1" means set PGE. */ on_each_cpu(adjust_pge, (void *)1, 0, 1); } unlock_cpu_hotplug(); } /* The Host side of lguest can be a module. This is a nice way for people to * play with it. */ module_init(init); module_exit(fini); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");