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>

diff --git a/arch/x86/include/asm/lguest.h b/arch/x86/include/asm/lguest.h
index e2d4a4afa8c3070374f3617fa405f5733b5624b1..3bbc07a57a31e9d68f232fd56651be6788491f95 100644 (file)
--- 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 543510a2f9e0f699586df06acb89cbcb1426863e..13616d708389d759b7ee90101191a89b24b4131f 100644 (file)
--- 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 81678bf0fcb7e594f0fad1d87fc1cbbf35c65277..d5ae63f5ec5d8d8836a4391c29cca8ecc9742c9e 100644 (file)
--- 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 1219af493c0f186bf0ccc71c5bac6b8c88564dbb..19a32280731db99e05661d3ae5c46b6a8f168dd2 100644 (file)
--- 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 70dfcdc29f1f9e9d8cfc764d69ab7a965daf5c25..6d4c072b61e19e39c2e2c21459d8fef71776fb2e 100644 (file)
--- 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 307e8b39e7d1dd2b0bdbe69bbefb6ca36b7b5567..ac8ad0461e809db526bfc1db1ca2290ac612a43d 100644 (file)
--- 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 9962c6bb1311f199ce91600d22724fd7599020dd..6db19f35f7c51e9d3206d8d839724bcfb6256a5d 100644 (file)
--- 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). */