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Commit d7e28ffe authored by Rusty Russell's avatar Rusty Russell Committed by Linus Torvalds
Browse files

lguest: the host code 



This is the code for the "lg.ko" module, which allows lguest guests to
be launched.

[akpm@linux-foundation.org: update for futex-new-private-futexes]
[akpm@linux-foundation.org: build fix]
[jmorris@namei.org: lguest: use hrtimers]
[akpm@linux-foundation.org: x86_64 build fix]
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Eric Dumazet <dada1@cosmosbay.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 07ad157f

arch/i386/kernel/tsc.c

+3 −1
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ static int tsc_enabled; 
 * an extra value to store the TSC freq

 */

unsigned int tsc_khz;

EXPORT_SYMBOL_GPL(tsc_khz);



int tsc_disable;
@@ -58,10 +59,11 @@ __setup("notsc", tsc_setup); 
 */

static int tsc_unstable;



static inline int check_tsc_unstable(void)

int check_tsc_unstable(void)

{

	return tsc_unstable;

}

EXPORT_SYMBOL_GPL(check_tsc_unstable);



/* Accellerators for sched_clock()

 * convert from cycles(64bits) => nanoseconds (64bits)

arch/x86_64/kernel/tsc.c

+1 −1
Original line number Diff line number Diff line
@@ -44,7 +44,7 @@ unsigned long long sched_clock(void) 


static int tsc_unstable;



static inline int check_tsc_unstable(void)

inline int check_tsc_unstable(void)

{

	return tsc_unstable;

}

drivers/lguest/core.c

0 → 100644
+462 −0
Original line number Diff line number Diff line 
/* World's simplest hypervisor, to test paravirt_ops and show

 * unbelievers that virtualization is the future.  Plus, it's fun! */

#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]);

}



static __init int map_switcher(void)

{

	int i, err;

	struct page **pagep;



	switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES,

				GFP_KERNEL);

	if (!switcher_page) {

		err = -ENOMEM;

		goto out;

	}



	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);

	}



	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;

	}



	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;

	}

	memcpy(switcher_vma->addr, start_switcher_text,

	       end_switcher_text - start_switcher_text);



	/* Fix up IDT entries to point into copied text. */

	for (i = 0; i < IDT_ENTRIES; i++)

		default_idt_entries[i] += switcher_offset();



	for_each_possible_cpu(i) {

		struct lguest_pages *pages = lguest_pages(i);

		struct lguest_ro_state *state = &pages->state;



		/* These fields are static: rest done in copy_in_guest_info */

		state->host_gdt_desc.size = GDT_SIZE-1;

		state->host_gdt_desc.address = (long)get_cpu_gdt_table(i);

		store_idt(&state->host_idt_desc);

		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;

		state->guest_tss.esp0 = (long)(&pages->regs + 1);

		state->guest_tss.ss0 = LGUEST_DS;

		/* No I/O for you! */

		state->guest_tss.io_bitmap_base = sizeof(state->guest_tss);

		setup_default_gdt_entries(state);

		setup_default_idt_entries(state, default_idt_entries);



		/* Setup LGUEST segments on all cpus */

		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_CS] = FULL_EXEC_SEGMENT;

		get_cpu_gdt_table(i)[GDT_ENTRY_LGUEST_DS] = FULL_SEGMENT;

	}



	/* Initialize entry point into switcher. */

	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);

	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;

}



static void unmap_switcher(void)

{

	unsigned int i;



	vunmap(switcher_vma->addr);

	for (i = 0; i < TOTAL_SWITCHER_PAGES; i++)

		__free_pages(switcher_page[i], 0);

}



/* IN/OUT insns: enough to get us past boot-time probing. */

static int emulate_insn(struct lguest *lg)

{

	u8 insn;

	unsigned int insnlen = 0, in = 0, shift = 0;

	unsigned long physaddr = guest_pa(lg, lg->regs->eip);



	/* This only works for addresses in linear mapping... */

	if (lg->regs->eip < lg->page_offset)

		return 0;

	lgread(lg, &insn, physaddr, 1);



	/* Operand size prefix means it's actually for ax. */

	if (insn == 0x66) {

		shift = 16;

		insnlen = 1;

		lgread(lg, &insn, physaddr + insnlen, 1);

	}



	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:

		return 0;

	}



	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);

	}

	lg->regs->eip += insnlen;

	return 1;

}



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);

}



/* Just like get_user, but don't let guest access lguest binary. */

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;

}



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);

}



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);

	}

}



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);

}



static void set_ts(void)

{

	u32 cr0;



	cr0 = read_cr0();

	if (!(cr0 & 8))

		write_cr0(cr0|8);

}



static void copy_in_guest_info(struct lguest *lg, struct lguest_pages *pages)

{

	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 are pretty cheap, so we do them unconditionally. */

	pages->state.host_cr3 = __pa(current->mm->pgd);

	map_switcher_in_guest(lg, pages);

	pages->state.guest_tss.esp1 = lg->esp1;

	pages->state.guest_tss.ss1 = lg->ss1;



	/* Copy direct trap entries. */

	if (lg->changed & CHANGED_IDT)

		copy_traps(lg, pages->state.guest_idt, default_idt_entries);



	/* Copy all GDT entries but the TSS. */

	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);



	lg->changed = 0;

}



static void run_guest_once(struct lguest *lg, struct lguest_pages *pages)

{

	unsigned int clobber;



	copy_in_guest_info(lg, pages);



	/* Put eflags on stack, lcall does rest: suitable for iret return. */

	asm volatile("pushf; lcall *lguest_entry"

		     : "=a"(clobber), "=b"(clobber)

		     : "0"(pages), "1"(__pa(lg->pgdirs[lg->pgdidx].pgdir))

		     : "memory", "%edx", "%ecx", "%edi", "%esi");

}



int run_guest(struct lguest *lg, unsigned long __user *user)

{

	while (!lg->dead) {

		unsigned int cr2 = 0; /* Damn gcc */



		/* Hypercalls first: we might have been out to userspace */

		do_hypercalls(lg);

		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;

		}



		if (signal_pending(current))

			return -ERESTARTSYS;



		/* If Waker set break_out, return to Launcher. */

		if (lg->break_out)

			return -EAGAIN;



		maybe_do_interrupt(lg);



		try_to_freeze();



		if (lg->dead)

			break;



		if (lg->halted) {

			set_current_state(TASK_INTERRUPTIBLE);

			schedule();

			continue;

		}



		local_irq_disable();



		/* Even if *we* don't want FPU trap, guest might... */

		if (lg->ts)

			set_ts();



		/* Don't let Guest do SYSENTER: we can't handle it. */

		if (boot_cpu_has(X86_FEATURE_SEP))

			wrmsr(MSR_IA32_SYSENTER_CS, 0, 0);



		run_guest_once(lg, lguest_pages(raw_smp_processor_id()));



		/* Save cr2 now if we page-faulted. */

		if (lg->regs->trapnum == 14)

			cr2 = read_cr2();

		else if (lg->regs->trapnum == 7)

			math_state_restore();



		if (boot_cpu_has(X86_FEATURE_SEP))

			wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0);

		local_irq_enable();



		switch (lg->regs->trapnum) {

		case 13: /* We've intercepted a GPF. */

			if (lg->regs->errcode == 0) {

				if (emulate_insn(lg))

					continue;

			}

			break;

		case 14: /* We've intercepted a page fault. */

			if (demand_page(lg, cr2, lg->regs->errcode))

				continue;



			/* If lguest_data is NULL, this won't hurt. */

			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 they don't want to know, just absorb it. */

			if (!lg->ts)

				continue;

			break;

		case 32 ... 255: /* Real interrupt, fall thru */

			cond_resched();

		case LGUEST_TRAP_ENTRY: /* Handled at top of loop */

			continue;

		}



		if (deliver_trap(lg, lg->regs->trapnum))

			continue;



		kill_guest(lg, "unhandled trap %li at %#lx (%#lx)",

			   lg->regs->trapnum, lg->regs->eip,

			   lg->regs->trapnum == 14 ? cr2 : lg->regs->errcode);

	}

	return -ENOENT;

}



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);

}



static int __init init(void)

{

	int err;



	if (paravirt_enabled()) {

		printk("lguest is afraid of %s\n", paravirt_ops.name);

		return -EPERM;

	}



	err = map_switcher();

	if (err)

		return err;



	err = init_pagetables(switcher_page, SHARED_SWITCHER_PAGES);

	if (err) {

		unmap_switcher();

		return err;

	}

	lguest_io_init();



	err = lguest_device_init();

	if (err) {

		free_pagetables();

		unmap_switcher();

		return err;

	}

	lock_cpu_hotplug();

	if (cpu_has_pge) { /* We have a broader idea of "global". */

		cpu_had_pge = 1;

		on_each_cpu(adjust_pge, (void *)0, 0, 1);

		clear_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);

	}

	unlock_cpu_hotplug();

	return 0;

}



static void __exit fini(void)

{

	lguest_device_remove();

	free_pagetables();

	unmap_switcher();

	lock_cpu_hotplug();

	if (cpu_had_pge) {

		set_bit(X86_FEATURE_PGE, boot_cpu_data.x86_capability);

		on_each_cpu(adjust_pge, (void *)1, 0, 1);

	}

	unlock_cpu_hotplug();

}



module_init(init);

module_exit(fini);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("Rusty Russell <rusty@rustcorp.com.au>");

drivers/lguest/hypercalls.c

0 → 100644
+192 −0
Original line number Diff line number Diff line 
/*  Actual hypercalls, which allow guests to actually do something.

    Copyright (C) 2006 Rusty Russell IBM Corporation



    This program is free software; you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by

    the Free Software Foundation; either version 2 of the License, or

    (at your option) any later version.



    This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    GNU General Public License for more details.



    You should have received a copy of the GNU General Public License

    along with this program; if not, write to the Free Software

    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA

*/

#include <linux/uaccess.h>

#include <linux/syscalls.h>

#include <linux/mm.h>

#include <asm/page.h>

#include <asm/pgtable.h>

#include <irq_vectors.h>

#include "lg.h"



static void do_hcall(struct lguest *lg, struct lguest_regs *regs)

{

	switch (regs->eax) {

	case LHCALL_FLUSH_ASYNC:

		break;

	case LHCALL_LGUEST_INIT:

		kill_guest(lg, "already have lguest_data");

		break;

	case LHCALL_CRASH: {

		char msg[128];

		lgread(lg, msg, regs->edx, sizeof(msg));

		msg[sizeof(msg)-1] = '\0';

		kill_guest(lg, "CRASH: %s", msg);

		break;

	}

	case LHCALL_FLUSH_TLB:

		if (regs->edx)

			guest_pagetable_clear_all(lg);

		else

			guest_pagetable_flush_user(lg);

		break;

	case LHCALL_GET_WALLCLOCK: {

		struct timespec ts;

		ktime_get_real_ts(&ts);

		regs->eax = ts.tv_sec;

		break;

	}

	case LHCALL_BIND_DMA:

		regs->eax = bind_dma(lg, regs->edx, regs->ebx,

				     regs->ecx >> 8, regs->ecx & 0xFF);

		break;

	case LHCALL_SEND_DMA:

		send_dma(lg, regs->edx, regs->ebx);

		break;

	case LHCALL_LOAD_GDT:

		load_guest_gdt(lg, regs->edx, regs->ebx);

		break;

	case LHCALL_LOAD_IDT_ENTRY:

		load_guest_idt_entry(lg, regs->edx, regs->ebx, regs->ecx);

		break;

	case LHCALL_NEW_PGTABLE:

		guest_new_pagetable(lg, regs->edx);

		break;

	case LHCALL_SET_STACK:

		guest_set_stack(lg, regs->edx, regs->ebx, regs->ecx);

		break;

	case LHCALL_SET_PTE:

		guest_set_pte(lg, regs->edx, regs->ebx, mkgpte(regs->ecx));

		break;

	case LHCALL_SET_PMD:

		guest_set_pmd(lg, regs->edx, regs->ebx);

		break;

	case LHCALL_LOAD_TLS:

		guest_load_tls(lg, regs->edx);

		break;

	case LHCALL_SET_CLOCKEVENT:

		guest_set_clockevent(lg, regs->edx);

		break;

	case LHCALL_TS:

		lg->ts = regs->edx;

		break;

	case LHCALL_HALT:

		lg->halted = 1;

		break;

	default:

		kill_guest(lg, "Bad hypercall %li\n", regs->eax);

	}

}



/* We always do queued calls before actual hypercall. */

static void do_async_hcalls(struct lguest *lg)

{

	unsigned int i;

	u8 st[LHCALL_RING_SIZE];



	if (copy_from_user(&st, &lg->lguest_data->hcall_status, sizeof(st)))

		return;



	for (i = 0; i < ARRAY_SIZE(st); i++) {

		struct lguest_regs regs;

		unsigned int n = lg->next_hcall;



		if (st[n] == 0xFF)

			break;



		if (++lg->next_hcall == LHCALL_RING_SIZE)

			lg->next_hcall = 0;



		if (get_user(regs.eax, &lg->lguest_data->hcalls[n].eax)

		    || get_user(regs.edx, &lg->lguest_data->hcalls[n].edx)

		    || get_user(regs.ecx, &lg->lguest_data->hcalls[n].ecx)

		    || get_user(regs.ebx, &lg->lguest_data->hcalls[n].ebx)) {

			kill_guest(lg, "Fetching async hypercalls");

			break;

		}



		do_hcall(lg, &regs);

		if (put_user(0xFF, &lg->lguest_data->hcall_status[n])) {

			kill_guest(lg, "Writing result for async hypercall");

			break;

		}



		if (lg->dma_is_pending)

			break;

	}

}



static void initialize(struct lguest *lg)

{

	u32 tsc_speed;



	if (lg->regs->eax != LHCALL_LGUEST_INIT) {

		kill_guest(lg, "hypercall %li before LGUEST_INIT",

			   lg->regs->eax);

		return;

	}



	/* We only tell the guest to use the TSC if it's reliable. */

	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) && !check_tsc_unstable())

		tsc_speed = tsc_khz;

	else

		tsc_speed = 0;



	lg->lguest_data = (struct lguest_data __user *)lg->regs->edx;

	/* We check here so we can simply copy_to_user/from_user */

	if (!lguest_address_ok(lg, lg->regs->edx, sizeof(*lg->lguest_data))) {

		kill_guest(lg, "bad guest page %p", lg->lguest_data);

		return;

	}

	if (get_user(lg->noirq_start, &lg->lguest_data->noirq_start)

	    || get_user(lg->noirq_end, &lg->lguest_data->noirq_end)

	    /* We reserve the top pgd entry. */

	    || put_user(4U*1024*1024, &lg->lguest_data->reserve_mem)

	    || put_user(tsc_speed, &lg->lguest_data->tsc_khz)

	    || put_user(lg->guestid, &lg->lguest_data->guestid))

		kill_guest(lg, "bad guest page %p", lg->lguest_data);



	/* This is the one case where the above accesses might have

	 * been the first write to a Guest page.  This may have caused

	 * a copy-on-write fault, but the Guest might be referring to

	 * the old (read-only) page. */

	guest_pagetable_clear_all(lg);

}



/* Even if we go out to userspace and come back, we don't want to do

 * the hypercall again. */

static void clear_hcall(struct lguest *lg)

{

	lg->regs->trapnum = 255;

}



void do_hypercalls(struct lguest *lg)

{

	if (unlikely(!lg->lguest_data)) {

		if (lg->regs->trapnum == LGUEST_TRAP_ENTRY) {

			initialize(lg);

			clear_hcall(lg);

		}

		return;

	}



	do_async_hcalls(lg);

	if (!lg->dma_is_pending && lg->regs->trapnum == LGUEST_TRAP_ENTRY) {

		do_hcall(lg, lg->regs);

		clear_hcall(lg);

	}

}

drivers/lguest/interrupts_and_traps.c

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Original line number Diff line number Diff line 
#include <linux/uaccess.h>

#include "lg.h"



static unsigned long idt_address(u32 lo, u32 hi)

{

	return (lo & 0x0000FFFF) | (hi & 0xFFFF0000);

}



static int idt_type(u32 lo, u32 hi)

{

	return (hi >> 8) & 0xF;

}



static int idt_present(u32 lo, u32 hi)

{

	return (hi & 0x8000);

}



static void push_guest_stack(struct lguest *lg, unsigned long *gstack, u32 val)

{

	*gstack -= 4;

	lgwrite_u32(lg, *gstack, val);

}



static void set_guest_interrupt(struct lguest *lg, u32 lo, u32 hi, int has_err)

{

	unsigned long gstack;

	u32 eflags, ss, irq_enable;



	/* If they want a ring change, we use new stack and push old ss/esp */

	if ((lg->regs->ss&0x3) != GUEST_PL) {

		gstack = guest_pa(lg, lg->esp1);

		ss = lg->ss1;

		push_guest_stack(lg, &gstack, lg->regs->ss);

		push_guest_stack(lg, &gstack, lg->regs->esp);

	} else {

		gstack = guest_pa(lg, lg->regs->esp);

		ss = lg->regs->ss;

	}



	/* We use IF bit in eflags to indicate whether irqs were disabled

	   (it's always 0, since irqs are enabled when guest is running). */

	eflags = lg->regs->eflags;

	if (get_user(irq_enable, &lg->lguest_data->irq_enabled))

		irq_enable = 0;

	eflags |= (irq_enable & X86_EFLAGS_IF);



	push_guest_stack(lg, &gstack, eflags);

	push_guest_stack(lg, &gstack, lg->regs->cs);

	push_guest_stack(lg, &gstack, lg->regs->eip);



	if (has_err)

		push_guest_stack(lg, &gstack, lg->regs->errcode);



	/* Change the real stack so switcher returns to trap handler */

	lg->regs->ss = ss;

	lg->regs->esp = gstack + lg->page_offset;

	lg->regs->cs = (__KERNEL_CS|GUEST_PL);

	lg->regs->eip = idt_address(lo, hi);



	/* Disable interrupts for an interrupt gate. */

	if (idt_type(lo, hi) == 0xE)

		if (put_user(0, &lg->lguest_data->irq_enabled))

			kill_guest(lg, "Disabling interrupts");

}



void maybe_do_interrupt(struct lguest *lg)

{

	unsigned int irq;

	DECLARE_BITMAP(blk, LGUEST_IRQS);

	struct desc_struct *idt;



	if (!lg->lguest_data)

		return;



	/* Mask out any interrupts they have blocked. */

	if (copy_from_user(&blk, lg->lguest_data->blocked_interrupts,

			   sizeof(blk)))

		return;



	bitmap_andnot(blk, lg->irqs_pending, blk, LGUEST_IRQS);



	irq = find_first_bit(blk, LGUEST_IRQS);

	if (irq >= LGUEST_IRQS)

		return;



	if (lg->regs->eip >= lg->noirq_start && lg->regs->eip < lg->noirq_end)

		return;



	/* If they're halted, we re-enable interrupts. */

	if (lg->halted) {

		/* Re-enable interrupts. */

		if (put_user(X86_EFLAGS_IF, &lg->lguest_data->irq_enabled))

			kill_guest(lg, "Re-enabling interrupts");

		lg->halted = 0;

	} else {

		/* Maybe they have interrupts disabled? */

		u32 irq_enabled;

		if (get_user(irq_enabled, &lg->lguest_data->irq_enabled))

			irq_enabled = 0;

		if (!irq_enabled)

			return;

	}



	idt = &lg->idt[FIRST_EXTERNAL_VECTOR+irq];

	if (idt_present(idt->a, idt->b)) {

		clear_bit(irq, lg->irqs_pending);

		set_guest_interrupt(lg, idt->a, idt->b, 0);

	}

}



static int has_err(unsigned int trap)

{

	return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17);

}



int deliver_trap(struct lguest *lg, unsigned int num)

{

	u32 lo = lg->idt[num].a, hi = lg->idt[num].b;



	if (!idt_present(lo, hi))

		return 0;

	set_guest_interrupt(lg, lo, hi, has_err(num));

	return 1;

}



static int direct_trap(const struct lguest *lg,

		       const struct desc_struct *trap,

		       unsigned int num)

{

	/* Hardware interrupts don't go to guest (except syscall). */

	if (num >= FIRST_EXTERNAL_VECTOR && num != SYSCALL_VECTOR)

		return 0;



	/* We intercept page fault (demand shadow paging & cr2 saving)

	   protection fault (in/out emulation) and device not

	   available (TS handling), and hypercall */

	if (num == 14 || num == 13 || num == 7 || num == LGUEST_TRAP_ENTRY)

		return 0;



	/* Interrupt gates (0xE) or not present (0x0) can't go direct. */

	return idt_type(trap->a, trap->b) == 0xF;

}



void pin_stack_pages(struct lguest *lg)

{

	unsigned int i;



	for (i = 0; i < lg->stack_pages; i++)

		pin_page(lg, lg->esp1 - i * PAGE_SIZE);

}



void guest_set_stack(struct lguest *lg, u32 seg, u32 esp, unsigned int pages)

{

	/* You cannot have a stack segment with priv level 0. */

	if ((seg & 0x3) != GUEST_PL)

		kill_guest(lg, "bad stack segment %i", seg);

	if (pages > 2)

		kill_guest(lg, "bad stack pages %u", pages);

	lg->ss1 = seg;

	lg->esp1 = esp;

	lg->stack_pages = pages;

	pin_stack_pages(lg);

}



/* Set up trap in IDT. */

static void set_trap(struct lguest *lg, struct desc_struct *trap,

		     unsigned int num, u32 lo, u32 hi)

{

	u8 type = idt_type(lo, hi);



	if (!idt_present(lo, hi)) {

		trap->a = trap->b = 0;

		return;

	}



	if (type != 0xE && type != 0xF)

		kill_guest(lg, "bad IDT type %i", type);



	trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF);

	trap->b = (hi&0xFFFFEF00);

}



void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi)

{

	/* Guest never handles: NMI, doublefault, hypercall, spurious irq. */

	if (num == 2 || num == 8 || num == 15 || num == LGUEST_TRAP_ENTRY)

		return;



	lg->changed |= CHANGED_IDT;

	if (num < ARRAY_SIZE(lg->idt))

		set_trap(lg, &lg->idt[num], num, lo, hi);

	else if (num == SYSCALL_VECTOR)

		set_trap(lg, &lg->syscall_idt, num, lo, hi);

}



static void default_idt_entry(struct desc_struct *idt,

			      int trap,

			      const unsigned long handler)

{

	u32 flags = 0x8e00;



	/* They can't "int" into any of them except hypercall. */

	if (trap == LGUEST_TRAP_ENTRY)

		flags |= (GUEST_PL << 13);



	idt->a = (LGUEST_CS<<16) | (handler&0x0000FFFF);

	idt->b = (handler&0xFFFF0000) | flags;

}



void setup_default_idt_entries(struct lguest_ro_state *state,

			       const unsigned long *def)

{

	unsigned int i;



	for (i = 0; i < ARRAY_SIZE(state->guest_idt); i++)

		default_idt_entry(&state->guest_idt[i], i, def[i]);

}



void copy_traps(const struct lguest *lg, struct desc_struct *idt,

		const unsigned long *def)

{

	unsigned int i;



	/* All hardware interrupts are same whatever the guest: only the

	 * traps might be different. */

	for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) {

		if (direct_trap(lg, &lg->idt[i], i))

			idt[i] = lg->idt[i];

		else

			default_idt_entry(&idt[i], i, def[i]);

	}

	i = SYSCALL_VECTOR;

	if (direct_trap(lg, &lg->syscall_idt, i))

		idt[i] = lg->syscall_idt;

	else

		default_idt_entry(&idt[i], i, def[i]);

}



void guest_set_clockevent(struct lguest *lg, unsigned long delta)

{

	ktime_t expires;



	if (unlikely(delta == 0)) {

		/* Clock event device is shutting down. */

		hrtimer_cancel(&lg->hrt);

		return;

	}



	expires = ktime_add_ns(ktime_get_real(), delta);

	hrtimer_start(&lg->hrt, expires, HRTIMER_MODE_ABS);

}



static enum hrtimer_restart clockdev_fn(struct hrtimer *timer)

{

	struct lguest *lg = container_of(timer, struct lguest, hrt);



	set_bit(0, lg->irqs_pending);

	if (lg->halted)

		wake_up_process(lg->tsk);

	return HRTIMER_NORESTART;

}



void init_clockdev(struct lguest *lg)

{

	hrtimer_init(&lg->hrt, CLOCK_REALTIME, HRTIMER_MODE_ABS);

	lg->hrt.function = clockdev_fn;

}