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

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
...@@ -218,10 +218,9 @@ int deliver_trap(struct lguest *lg, unsigned int num) ...@@ -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 * system calls down from 1750ns to 270ns. Plus, if lguest didn't do it, all
* the other hypervisors would tease it. * the other hypervisors would tease it.
* *
* This routine determines if a trap can be delivered directly. */ * This routine indicates if a particular trap number could be delivered
static int direct_trap(const struct lguest *lg, * directly. */
const struct desc_struct *trap, static int direct_trap(unsigned int num)
unsigned int num)
{ {
/* Hardware interrupts don't go to the Guest at all (except system /* Hardware interrupts don't go to the Guest at all (except system
* call). */ * call). */
...@@ -232,14 +231,7 @@ static int direct_trap(const struct lguest *lg, ...@@ -232,14 +231,7 @@ static int direct_trap(const struct lguest *lg,
* fault address), general protection faults (in/out emulation) and * fault address), general protection faults (in/out emulation) and
* device not available (TS handling), and of course, the hypercall * device not available (TS handling), and of course, the hypercall
* trap. */ * trap. */
if (num == 14 || num == 13 || num == 7 || num == LGUEST_TRAP_ENTRY) return 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;
} }
/*:*/ /*:*/
...@@ -348,15 +340,11 @@ void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi) ...@@ -348,15 +340,11 @@ void load_guest_idt_entry(struct lguest *lg, unsigned int num, u32 lo, u32 hi)
* to copy this again. */ * to copy this again. */
lg->changed |= CHANGED_IDT; lg->changed |= CHANGED_IDT;
/* The IDT which we keep in "struct lguest" only contains 32 entries /* Check that the Guest doesn't try to step outside the bounds. */
* for the traps and LGUEST_IRQS (32) entries for interrupts. We if (num >= ARRAY_SIZE(lg->idt))
* ignore attempts to set handlers for higher interrupt numbers, except kill_guest(lg, "Setting idt entry %u", num);
* for the system call "interrupt" at 128: we have a special IDT entry else
* for that. */
if (num < ARRAY_SIZE(lg->idt))
set_trap(lg, &lg->idt[num], num, lo, hi); 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 /* 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, ...@@ -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 /* We can simply copy the direct traps, otherwise we use the default
* ones in the Switcher: they will return to the Host. */ * ones in the Switcher: they will return to the Host. */
for (i = 0; i < FIRST_EXTERNAL_VECTOR; i++) { for (i = 0; i < ARRAY_SIZE(lg->idt); i++) {
if (direct_trap(lg, &lg->idt[i], 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]; idt[i] = lg->idt[i];
else else
/* Reset it to the default. */
default_idt_entry(&idt[i], i, def[i]); 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) void guest_set_clockevent(struct lguest *lg, unsigned long delta)
......
...@@ -184,8 +184,7 @@ struct lguest ...@@ -184,8 +184,7 @@ struct lguest
struct desc_struct gdt[GDT_ENTRIES]; struct desc_struct gdt[GDT_ENTRIES];
/* The IDT entries: some copied into lguest_ro_state when running. */ /* The IDT entries: some copied into lguest_ro_state when running. */
struct desc_struct idt[FIRST_EXTERNAL_VECTOR+LGUEST_IRQS]; struct desc_struct idt[IDT_ENTRIES];
struct desc_struct syscall_idt;
/* Virtual clock device */ /* Virtual clock device */
struct hrtimer hrt; struct hrtimer hrt;
......
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