/* deliver_trap() returns true if it could deliver the trap. */
int deliver_trap(struct lg_cpu *cpu, unsigned int num)
{
/* Trap numbers are always 8 bit, but we set an impossible trap number
* for traps inside the Switcher, so check that here. */
if (num >= ARRAY_SIZE(cpu->arch.idt))
return 0;
/* Early on the Guest hasn't set the IDT entries (or maybe it put a
* bogus one in): if we fail here, the Guest will be killed. */
if (!idt_present(cpu->arch.idt[num].a, cpu->arch.idt[num].b))
return 0;
set_guest_interrupt(cpu, cpu->arch.idt[num].a,
cpu->arch.idt[num].b, has_err(num));
return 1;
}
/*H:235 This is the routine which actually checks the Guest's IDT entry and
* transfers it into the entry in "struct lguest": */
static void set_trap(struct lg_cpu *cpu, struct desc_struct *trap,
unsigned int num, u32 lo, u32 hi)
{
u8 type = idt_type(lo, hi);
/* We zero-out a not-present entry */
if (!idt_present(lo, hi)) {
trap->a = trap->b = 0;
return;
}
/* We only support interrupt and trap gates. */
if (type != 0xE && type != 0xF)
kill_guest(cpu, "bad IDT type %i", type);
/* We only copy the handler address, present bit, privilege level and
* type. The privilege level controls where the trap can be triggered
* manually with an "int" instruction. This is usually GUEST_PL,
* except for system calls which userspace can use. */
trap->a = ((__KERNEL_CS|GUEST_PL)<<16) | (lo&0x0000FFFF);
trap->b = (hi&0xFFFFEF00);
}
/*
* This actually diverts the Guest to running an interrupt handler, once an
* interrupt has been identified by interrupt_pending().
*/
void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
{
struct desc_struct *idt;
BUG_ON(irq >= LGUEST_IRQS);
/*
* They may be in the middle of an iret, where they asked us never to
* deliver interrupts.
*/
if (cpu->regs->eip >= cpu->lg->noirq_start &&
(cpu->regs->eip < cpu->lg->noirq_end))
return;
/* If they're halted, interrupts restart them. */
if (cpu->halted) {
/* Re-enable interrupts. */
if (put_user(X86_EFLAGS_IF, &cpu->lg->lguest_data->irq_enabled))
kill_guest(cpu, "Re-enabling interrupts");
cpu->halted = 0;
} else {
/* Otherwise we check if they have interrupts disabled. */
u32 irq_enabled;
if (get_user(irq_enabled, &cpu->lg->lguest_data->irq_enabled))
irq_enabled = 0;
if (!irq_enabled) {
/* Make sure they know an IRQ is pending. */
put_user(X86_EFLAGS_IF,
&cpu->lg->lguest_data->irq_pending);
return;
}
}
/*
* Look at the IDT entry the Guest gave us for this interrupt. The
* first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip
* over them.
*/
idt = &cpu->arch.idt[FIRST_EXTERNAL_VECTOR+irq];
/* If they don't have a handler (yet?), we just ignore it */
if (idt_present(idt->a, idt->b)) {
/* OK, mark it no longer pending and deliver it. */
clear_bit(irq, cpu->irqs_pending);
/*
* set_guest_interrupt() takes the interrupt descriptor and a
* flag to say whether this interrupt pushes an error code onto
* the stack as well: virtual interrupts never do.
*/
set_guest_interrupt(cpu, idt->a, idt->b, false);
}
/*
* Every time we deliver an interrupt, we update the timestamp in the
* Guest's lguest_data struct. It would be better for the Guest if we
* did this more often, but it can actually be quite slow: doing it
* here is a compromise which means at least it gets updated every
* timer interrupt.
*/
write_timestamp(cpu);
/*
* If there are no other interrupts we want to deliver, clear
* the pending flag.
*/
if (!more)
put_user(0, &cpu->lg->lguest_data->irq_pending);
}
/*H:205
* Virtual Interrupts.
*
* maybe_do_interrupt() gets called before every entry to the Guest, to see if
* we should divert the Guest to running an interrupt handler. */
void maybe_do_interrupt(struct lg_cpu *cpu)
{
unsigned int irq;
DECLARE_BITMAP(blk, LGUEST_IRQS);
struct desc_struct *idt;
/* If the Guest hasn't even initialized yet, we can do nothing. */
if (!cpu->lg->lguest_data)
return;
/* Take our "irqs_pending" array and remove any interrupts the Guest
* wants blocked: the result ends up in "blk". */
if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts,
sizeof(blk)))
return;
bitmap_andnot(blk, cpu->irqs_pending, blk, LGUEST_IRQS);
/* Find the first interrupt. */
irq = find_first_bit(blk, LGUEST_IRQS);
/* None? Nothing to do */
if (irq >= LGUEST_IRQS)
return;
/* They may be in the middle of an iret, where they asked us never to
* deliver interrupts. */
if (cpu->regs->eip >= cpu->lg->noirq_start &&
(cpu->regs->eip < cpu->lg->noirq_end))
return;
/* If they're halted, interrupts restart them. */
if (cpu->halted) {
/* Re-enable interrupts. */
if (put_user(X86_EFLAGS_IF, &cpu->lg->lguest_data->irq_enabled))
kill_guest(cpu, "Re-enabling interrupts");
cpu->halted = 0;
} else {
/* Otherwise we check if they have interrupts disabled. */
u32 irq_enabled;
if (get_user(irq_enabled, &cpu->lg->lguest_data->irq_enabled))
irq_enabled = 0;
if (!irq_enabled)
return;
}
/* Look at the IDT entry the Guest gave us for this interrupt. The
* first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip
* over them. */
idt = &cpu->arch.idt[FIRST_EXTERNAL_VECTOR+irq];
/* If they don't have a handler (yet?), we just ignore it */
if (idt_present(idt->a, idt->b)) {
/* OK, mark it no longer pending and deliver it. */
clear_bit(irq, cpu->irqs_pending);
/* set_guest_interrupt() takes the interrupt descriptor and a
* flag to say whether this interrupt pushes an error code onto
* the stack as well: virtual interrupts never do. */
set_guest_interrupt(cpu, idt->a, idt->b, 0);
}
/* Every time we deliver an interrupt, we update the timestamp in the
* Guest's lguest_data struct. It would be better for the Guest if we
* did this more often, but it can actually be quite slow: doing it
* here is a compromise which means at least it gets updated every
* timer interrupt. */
write_timestamp(cpu);
}
/*
* This actually diverts the Guest to running an interrupt handler, once an
* interrupt has been identified by interrupt_pending().
*/
void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
{
struct desc_struct *idt;
BUG_ON(irq >= LGUEST_IRQS);
/* If they're halted, interrupts restart them. */
if (cpu->halted) {
/* Re-enable interrupts. */
if (put_user(X86_EFLAGS_IF, &cpu->lg->lguest_data->irq_enabled))
kill_guest(cpu, "Re-enabling interrupts");
cpu->halted = 0;
} else {
/* Otherwise we check if they have interrupts disabled. */
u32 irq_enabled;
if (get_user(irq_enabled, &cpu->lg->lguest_data->irq_enabled))
irq_enabled = 0;
if (!irq_enabled) {
/* Make sure they know an IRQ is pending. */
put_user(X86_EFLAGS_IF,
&cpu->lg->lguest_data->irq_pending);
return;
}
}
/*
* Look at the IDT entry the Guest gave us for this interrupt. The
* first 32 (FIRST_EXTERNAL_VECTOR) entries are for traps, so we skip
* over them.
*/
idt = &cpu->arch.idt[FIRST_EXTERNAL_VECTOR+irq];
/* If they don't have a handler (yet?), we just ignore it */
if (idt_present(idt->a, idt->b)) {
/* OK, mark it no longer pending and deliver it. */
clear_bit(irq, cpu->irqs_pending);
/*
* They may be about to iret, where they asked us never to
* deliver interrupts. In this case, we can emulate that iret
* then immediately deliver the interrupt. This is basically
* a noop: the iret would pop the interrupt frame and restore
* eflags, and then we'd set it up again. So just restore the
* eflags word and jump straight to the handler in this case.
*
* Denys Vlasenko points out that this isn't quite right: if
* the iret was returning to userspace, then that interrupt
* would reset the stack pointer (which the Guest told us
* about via LHCALL_SET_STACK). But unless the Guest is being
* *really* weird, that will be the same as the current stack
* anyway.
*/
if (cpu->regs->eip == cpu->lg->noirq_iret) {
restore_eflags(cpu);
} else {
/*
* set_guest_interrupt() takes a flag to say whether
* this interrupt pushes an error code onto the stack
* as well: virtual interrupts never do.
*/
push_guest_interrupt_stack(cpu, false);
}
/* Actually make Guest cpu jump to handler. */
guest_run_interrupt(cpu, idt->a, idt->b);
}
/*
* Every time we deliver an interrupt, we update the timestamp in the
* Guest's lguest_data struct. It would be better for the Guest if we
* did this more often, but it can actually be quite slow: doing it
* here is a compromise which means at least it gets updated every
* timer interrupt.
*/
write_timestamp(cpu);
/*
* If there are no other interrupts we want to deliver, clear
* the pending flag.
*/
if (!more)
put_user(0, &cpu->lg->lguest_data->irq_pending);
}
