Re: [PATCH] lguest: simplify lguest_iret
Denys Vlasenko writes:
> On 03/23/2015 04:30 AM, Rusty Russell wrote:
>> + * 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 bascially
>> + * 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.
>> */
>> +if (cpu->regs->eip >= cpu->lg->noirq_start &&
>> +(cpu->regs->eip < cpu->lg->noirq_end)) {
>> +restore_eflags(cpu);
>
> In truth, this is not _exactly_ true for irets to CPL3.
>
> If a new interrupt comes right after iret, then
> a new transition to CPL0 will happen.
>
> This means ss:esp will be loaded from tss.ss0:tss.sp0.
>
> Meaning, that the new iret frame may be in a different place
> than the one which was used by iret.
True. We could check the to-be-restored-CPL and reset the sp. Instead,
I've added this comment:
/*
* 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.
*/
> There is no good reason for CPL0 code to move iret frame around,
> but who knows. As an example, look what 32-bit Linux kernel does
> with NMI iret frames... it's mind bending.
Fortunately, lguest is allergic to NMIs :)
Thanks!
Rusty.
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Re: [PATCH] lguest: simplify lguest_iret
On 03/23/2015 04:30 AM, Rusty Russell wrote:
> Denys Vlasenko writes:
>> Signed-off-by: Denys Vlasenko
>> CC: lgu...@lists.ozlabs.org
>> CC: x...@kernel.org
>> CC: linux-kernel@vger.kernel.org
>
> Oh, thanks, applied!
>
> And now it's down to one instruction, we could change
> try_deliver_interrupt() to handle this case (rather than ignoring the
> interrupt altogether): just jump to the handler and leave the
> stack set up.
>
> Here's a pair of inline patches which attempt to do that (untested!).
>
> Thanks,
> Rusty.
>
> 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
>
> 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 ac4453d8520e..4c8cf656f21f 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 583732cc5d18..128fe93161b4 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, >lg->lguest_data->noirq_start)
> - || get_user(cpu->lg->noirq_end, >lg->lguest_data->noirq_end))
> + if (get_user(cpu->lg->noirq_iret, >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
> ---
Re: [PATCH] lguest: simplify lguest_iret
On 03/23/2015 04:30 AM, Rusty Russell wrote:
Denys Vlasenko dvlas...@redhat.com writes:
Signed-off-by: Denys Vlasenko dvlas...@redhat.com
CC: lgu...@lists.ozlabs.org
CC: x...@kernel.org
CC: linux-kernel@vger.kernel.org
Oh, thanks, applied!
And now it's down to one instruction, we could change
try_deliver_interrupt() to handle this case (rather than ignoring the
interrupt altogether): just jump to the handler and leave the
stack set up.
Here's a pair of inline patches which attempt to do that (untested!).
Thanks,
Rusty.
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 ru...@rustcorp.com.au
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 ac4453d8520e..4c8cf656f21f 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 583732cc5d18..128fe93161b4 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 @@
Re: [PATCH] lguest: simplify lguest_iret
Denys Vlasenko dvlas...@redhat.com writes:
On 03/23/2015 04:30 AM, Rusty Russell wrote:
+ * 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 bascially
+ * 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.
*/
+if (cpu-regs-eip = cpu-lg-noirq_start
+(cpu-regs-eip cpu-lg-noirq_end)) {
+restore_eflags(cpu);
In truth, this is not _exactly_ true for irets to CPL3.
If a new interrupt comes right after iret, then
a new transition to CPL0 will happen.
This means ss:esp will be loaded from tss.ss0:tss.sp0.
Meaning, that the new iret frame may be in a different place
than the one which was used by iret.
True. We could check the to-be-restored-CPL and reset the sp. Instead,
I've added this comment:
/*
* 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.
*/
There is no good reason for CPL0 code to move iret frame around,
but who knows. As an example, look what 32-bit Linux kernel does
with NMI iret frames... it's mind bending.
Fortunately, lguest is allergic to NMIs :)
Thanks!
Rusty.
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH] lguest: simplify lguest_iret
Denys Vlasenko writes:
> Signed-off-by: Denys Vlasenko
> CC: lgu...@lists.ozlabs.org
> CC: x...@kernel.org
> CC: linux-kernel@vger.kernel.org
Oh, thanks, applied!
And now it's down to one instruction, we could change
try_deliver_interrupt() to handle this case (rather than ignoring the
interrupt altogether): just jump to the handler and leave the
stack set up.
Here's a pair of inline patches which attempt to do that (untested!).
Thanks,
Rusty.
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
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 ac4453d8520e..4c8cf656f21f 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 583732cc5d18..128fe93161b4 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, >lg->lguest_data->noirq_start)
- || get_user(cpu->lg->noirq_end, >lg->lguest_data->noirq_end))
+ if (get_user(cpu->lg->noirq_iret, >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
*
Re: [PATCH] lguest: simplify lguest_iret
Denys Vlasenko dvlas...@redhat.com writes:
Signed-off-by: Denys Vlasenko dvlas...@redhat.com
CC: lgu...@lists.ozlabs.org
CC: x...@kernel.org
CC: linux-kernel@vger.kernel.org
Oh, thanks, applied!
And now it's down to one instruction, we could change
try_deliver_interrupt() to handle this case (rather than ignoring the
interrupt altogether): just jump to the handler and leave the
stack set up.
Here's a pair of inline patches which attempt to do that (untested!).
Thanks,
Rusty.
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 ru...@rustcorp.com.au
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 ac4453d8520e..4c8cf656f21f 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 583732cc5d18..128fe93161b4 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
