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Commit 2f921b5b authored by Rusty Russell's avatar Rusty Russell
Browse files

lguest: suppress interrupts for single insn, not range. 



The last patch reduced our interrupt-suppression region to one address,
so simplify the code somewhat.

Also, remove the obsolete undefined instruction ranges and the comment
which refers to lguest_guest.S instead of head_32.S.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent 7042cb4e

arch/x86/include/asm/lguest.h

+2 −5
Original line number Diff line number Diff line
@@ -20,13 +20,10 @@ extern unsigned long switcher_addr; 
/* Found in switcher.S */

extern unsigned long default_idt_entries[];



/* Declarations for definitions in lguest_guest.S */

extern char lguest_noirq_start[], lguest_noirq_end[];

/* Declarations for definitions in arch/x86/lguest/head_32.S */

extern char lguest_noirq_iret[];

extern const char lgstart_cli[], lgend_cli[];

extern const char lgstart_sti[], lgend_sti[];

extern const char lgstart_popf[], lgend_popf[];

extern const char lgstart_pushf[], lgend_pushf[];

extern const char lgstart_iret[], lgend_iret[];



extern void lguest_iret(void);

extern void lguest_init(void);

arch/x86/lguest/boot.c

+1 −2
Original line number Diff line number Diff line
@@ -87,8 +87,7 @@ 


struct lguest_data lguest_data = {

	.hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF },

	.noirq_start = (u32)lguest_noirq_start,

	.noirq_end = (u32)lguest_noirq_end,

	.noirq_iret = (u32)lguest_noirq_iret,

	.kernel_address = PAGE_OFFSET,

	.blocked_interrupts = { 1 }, /* Block timer interrupts */

	.syscall_vec = SYSCALL_VECTOR,

arch/x86/lguest/head_32.S

+6 −9
Original line number Diff line number Diff line
@@ -133,9 +133,8 @@ ENTRY(lg_restore_fl) 
	ret

/*:*/



/* These demark the EIP range where host should never deliver interrupts. */

.global lguest_noirq_start

.global lguest_noirq_end

/* These demark the EIP where host should never deliver interrupts. */

.global lguest_noirq_iret



/*M:004

 * When the Host reflects a trap or injects an interrupt into the Guest, it
@@ -174,12 +173,11 @@ ENTRY(lg_restore_fl) 
 *

 * The second is harder: copying eflags to lguest_data.irq_enabled will turn

 * interrupts on before we're finished, so we could be interrupted before we

 * return to userspace or wherever.  Our solution to this is to surround the

 * code with lguest_noirq_start: and lguest_noirq_end: labels.  We tell the

 * return to userspace or wherever.  Our solution to this is to tell the

 * Host that it is *never* to interrupt us there, even if interrupts seem to be

 * enabled. (It's not necessary to protect pop instruction, since

 * data gets updated only after it completes, so we end up surrounding

 * just one instruction, iret).

 * data gets updated only after it completes, so we only need to protect

 * one instruction, iret).

 */

ENTRY(lguest_iret)

	pushl	2*4(%esp)
@@ -190,6 +188,5 @@ ENTRY(lguest_iret) 
	 * prefix makes sure we use the stack segment, which is still valid.

	 */

	popl	%ss:lguest_data+LGUEST_DATA_irq_enabled

lguest_noirq_start:

lguest_noirq_iret:

	iret
 
lguest_noirq_end:

drivers/lguest/hypercalls.c

+2 −3
Original line number Diff line number Diff line
@@ -211,10 +211,9 @@ static void initialize(struct lg_cpu *cpu) 


	/*

	 * The Guest tells us where we're not to deliver interrupts by putting

	 * the range of addresses into "struct lguest_data".

	 * the instruction address into "struct lguest_data".

	 */

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

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

	if (get_user(cpu->lg->noirq_iret, &cpu->lg->lguest_data->noirq_iret))

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



	/*

drivers/lguest/interrupts_and_traps.c

+4 −4
Original line number Diff line number Diff line
@@ -204,8 +204,7 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more) 
	 * 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))

	if (cpu->regs->eip == cpu->lg->noirq_iret)

		return;



	/* If they're halted, interrupts restart them. */
@@ -395,8 +394,9 @@ static bool direct_trap(unsigned int num) 
 * The Guest has the ability to turn its interrupt gates into trap gates,

 * if it is careful.  The Host will let trap gates can go directly to the

 * Guest, but the Guest needs the interrupts atomically disabled for an

 * interrupt gate.  It can do this by pointing the trap gate at instructions

 * within noirq_start and noirq_end, where it can safely disable interrupts.

 * interrupt gate.  The Host could provide a mechanism to register more

 * "no-interrupt" regions, and the Guest could point the trap gate at

 * instructions within that region, where it can safely disable interrupts.

 */



/*M:006