Commit 56adbe9d authored by Rusty Russell's avatar Rusty Russell
Browse files

Make shadow IDT a complete IDT with 256 entries. 



This simplifies the code a little, in preparation for allowing
alternate system call vectors in guests (Plan 9 uses 0x40).

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 48245cc0

drivers/lguest/interrupts_and_traps.c

+19 −30
Original line number Diff line number Diff line
@@ -218,10 +218,9 @@ int deliver_trap(struct lguest *lg, unsigned int num) 
 * system calls down from 1750ns to 270ns.  Plus, if lguest didn't do it, all

 * the other hypervisors would tease it.

 *

 * This routine determines if a trap can be delivered directly. */

static int direct_trap(const struct lguest *lg,

		       const struct desc_struct *trap,

		       unsigned int num)

 * This routine indicates if a particular trap number could be delivered

 * directly. */

static int direct_trap(unsigned int num)

{

	/* Hardware interrupts don't go to the Guest at all (except system

	 * call). */
@@ -232,14 +231,7 @@ static int direct_trap(const struct lguest *lg, 
	 * fault address), general protection faults (in/out emulation) and

	 * device not available (TS handling), and of course, the hypercall

	 * trap. */

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

		return 0;



	/* Only trap gates (type 15) can go direct to the Guest.  Interrupt

	 * gates (type 14) disable interrupts as they are entered, which we

	 * never let the Guest do.  Not present entries (type 0x0) also can't

	 * go direct, of course 8) */

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

	return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY;

}

/*:*/
@@ -348,15 +340,11 @@ void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi) 
	 * to copy this again. */

	lg->changed |= CHANGED_IDT;



	/* The IDT which we keep in "struct lguest" only contains 32 entries

	 * for the traps and LGUEST_IRQS (32) entries for interrupts.  We

	 * ignore attempts to set handlers for higher interrupt numbers, except

	 * for the system call "interrupt" at 128: we have a special IDT entry

	 * for that. */

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

	/* Check that the Guest doesn't try to step outside the bounds. */

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

		kill_guest(lg, "Setting idt entry %u", num);

	else

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

	else if (num == SYSCALL_VECTOR)

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

}



/* The default entry for each interrupt points into the Switcher routines which
@@ -399,20 +387,21 @@ void copy_traps(const struct lguest *lg, struct desc_struct *idt, 


	/* We can simply copy the direct traps, otherwise we use the default

	 * ones in the Switcher: they will return to the Host. */

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

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

	for (i = 0; i < ARRAY_SIZE(lg->idt); i++) {

		/* If no Guest can ever override this trap, leave it alone. */

		if (!direct_trap(i))

			continue;



		/* Only trap gates (type 15) can go direct to the Guest.

		 * Interrupt gates (type 14) disable interrupts as they are

		 * entered, which we never let the Guest do.  Not present

		 * entries (type 0x0) also can't go direct, of course. */

		if (idt_type(lg->idt[i].a, lg->idt[i].b) == 0xF)

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

		else

			/* Reset it to the default. */

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

	}



	/* Don't forget the system call trap!  The IDT entries for other

	 * interupts never change, so no need to copy them. */

	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)

drivers/lguest/lg.h

+1 −2
Original line number Diff line number Diff line
@@ -184,8 +184,7 @@ struct lguest 
	struct desc_struct gdt[GDT_ENTRIES];



	/* The IDT entries: some copied into lguest_ro_state when running. */

	struct desc_struct idt[FIRST_EXTERNAL_VECTOR+LGUEST_IRQS];

	struct desc_struct syscall_idt;

	struct desc_struct idt[IDT_ENTRIES];



	/* Virtual clock device */

	struct hrtimer hrt;