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authorRusty Russell <rusty@rustcorp.com.au>2015-03-24 04:21:39 +0300
committerRusty Russell <rusty@rustcorp.com.au>2015-03-24 04:22:08 +0300
commit2f921b5bb0511fb698681d8ef35c48be7a9116bf (patch)
treee4f07e4d66f47c7af9142bf13e5851a77acec77f
parent7042cb4eb30967b5eb9eeba04907882f04d6b6e5 (diff)
downloadlinux-2f921b5bb0511fb698681d8ef35c48be7a9116bf.tar.xz
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: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--arch/x86/include/asm/lguest.h7
-rw-r--r--arch/x86/lguest/boot.c3
-rw-r--r--arch/x86/lguest/head_32.S15
-rw-r--r--drivers/lguest/hypercalls.c5
-rw-r--r--drivers/lguest/interrupts_and_traps.c8
-rw-r--r--drivers/lguest/lg.h2
-rw-r--r--include/linux/lguest.h4
7 files changed, 18 insertions, 26 deletions
diff --git a/arch/x86/include/asm/lguest.h b/arch/x86/include/asm/lguest.h
index e2d4a4afa8c3..3bbc07a57a31 100644
--- a/arch/x86/include/asm/lguest.h
+++ b/arch/x86/include/asm/lguest.h
@@ -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);
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 543510a2f9e0..13616d708389 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -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,
diff --git a/arch/x86/lguest/head_32.S b/arch/x86/lguest/head_32.S
index 81678bf0fcb7..d5ae63f5ec5d 100644
--- a/arch/x86/lguest/head_32.S
+++ b/arch/x86/lguest/head_32.S
@@ -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:
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
index 1219af493c0f..19a32280731d 100644
--- a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -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);
/*
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index 70dfcdc29f1f..6d4c072b61e1 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -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
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 307e8b39e7d1..ac8ad0461e80 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -102,7 +102,7 @@ struct lguest {
struct pgdir pgdirs[4];
- unsigned long noirq_start, noirq_end;
+ unsigned long noirq_iret;
unsigned int stack_pages;
u32 tsc_khz;
diff --git a/include/linux/lguest.h b/include/linux/lguest.h
index 9962c6bb1311..6db19f35f7c5 100644
--- a/include/linux/lguest.h
+++ b/include/linux/lguest.h
@@ -61,8 +61,8 @@ struct lguest_data {
u32 tsc_khz;
/* Fields initialized by the Guest at boot: */
- /* Instruction range to suppress interrupts even if enabled */
- unsigned long noirq_start, noirq_end;
+ /* Instruction to suppress interrupts even if enabled */
+ unsigned long noirq_iret;
/* Address above which page tables are all identical. */
unsigned long kernel_address;
/* The vector to try to use for system calls (0x40 or 0x80). */