3 files changed, 21 insertions, 24 deletions

diff --git a/arch/x86/lguest/Kconfig b/arch/x86/lguest/Kconfig
index 4a0890f815c4..08f41caada45 100644
--- a/arch/x86/lguest/Kconfig
+++ b/arch/x86/lguest/Kconfig
@@ -1,6 +1,6 @@
 config LGUEST_GUEST
 	bool "Lguest guest support"
-	depends on X86_32 && PARAVIRT
+	depends on X86_32 && PARAVIRT && PCI
 	select TTY
 	select VIRTUALIZATION
 	select VIRTIO
@@ -8,7 +8,7 @@ config LGUEST_GUEST
 	help
 	  Lguest is a tiny in-kernel hypervisor.  Selecting this will
 	  allow your kernel to boot under lguest.  This option will increase
-	  your kernel size by about 6k.  If in doubt, say N.
+	  your kernel size by about 10k.  If in doubt, say N.
 
 	  If you say Y here, make sure you say Y (or M) to the virtio block
 	  and net drivers which lguest needs.
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index ac4453d8520e..8f9a133cc099 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,
@@ -262,7 +261,7 @@ PV_CALLEE_SAVE_REGS_THUNK(lguest_save_fl);
 PV_CALLEE_SAVE_REGS_THUNK(lguest_irq_disable);
 /*:*/
 
-/* These are in i386_head.S */
+/* These are in head_32.S */
 extern void lg_irq_enable(void);
 extern void lg_restore_fl(unsigned long flags);
 
@@ -868,7 +867,8 @@ static void __init lguest_init_IRQ(void)
 		/* Some systems map "vectors" to interrupts weirdly.  Not us! */
 		__this_cpu_write(vector_irq[i], i - FIRST_EXTERNAL_VECTOR);
 		if (i != SYSCALL_VECTOR)
-			set_intr_gate(i, interrupt[i - FIRST_EXTERNAL_VECTOR]);
+			set_intr_gate(i, irq_entries_start +
+					8 * (i - FIRST_EXTERNAL_VECTOR));
 	}
 
 	/*
@@ -1076,6 +1076,7 @@ static void lguest_load_sp0(struct tss_struct *tss,
 {
 	lazy_hcall3(LHCALL_SET_STACK, __KERNEL_DS | 0x1, thread->sp0,
 		   THREAD_SIZE / PAGE_SIZE);
+	tss->x86_tss.sp0 = thread->sp0;
 }
 
 /* Let's just say, I wouldn't do debugging under a Guest. */
@@ -1366,7 +1367,7 @@ static void lguest_restart(char *reason)
  * fit comfortably.
  *
  * First we need assembly templates of each of the patchable Guest operations,
- * and these are in i386_head.S.
+ * and these are in head_32.S.
  */
 
 /*G:060 We construct a table from the assembler templates: */
diff --git a/arch/x86/lguest/head_32.S b/arch/x86/lguest/head_32.S
index 6ddfe4fc23c3..d5ae63f5ec5d 100644
--- a/arch/x86/lguest/head_32.S
+++ b/arch/x86/lguest/head_32.S
@@ -84,7 +84,7 @@ ENTRY(lg_irq_enable)
 	 * set lguest_data.irq_pending to X86_EFLAGS_IF.  If it's not zero, we
 	 * jump to send_interrupts, otherwise we're done.
 	 */
-	testl $0, lguest_data+LGUEST_DATA_irq_pending
+	cmpl $0, lguest_data+LGUEST_DATA_irq_pending
 	jnz send_interrupts
 	/*
 	 * One cool thing about x86 is that you can do many things without using
@@ -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
@@ -168,29 +167,26 @@ ENTRY(lg_restore_fl)
  * So we have to copy eflags from the stack to lguest_data.irq_enabled before
  * we do the "iret".
  *
- * There are two problems with this: firstly, we need to use a register to do
- * the copy and secondly, the whole thing needs to be atomic.  The first
- * problem is easy to solve: push %eax on the stack so we can use it, and then
- * restore it at the end just before the real "iret".
+ * There are two problems with this: firstly, we can't clobber any registers
+ * and secondly, the whole thing needs to be atomic.  The first problem
+ * is solved by using "push memory"/"pop memory" instruction pair for copying.
  *
  * 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.
+ * enabled. (It's not necessary to protect pop instruction, since
+ * data gets updated only after it completes, so we only need to protect
+ * one instruction, iret).
  */
 ENTRY(lguest_iret)
-	pushl	%eax
-	movl	12(%esp), %eax
-lguest_noirq_start:
+	pushl	2*4(%esp)
 	/*
 	 * Note the %ss: segment prefix here.  Normal data accesses use the
 	 * "ds" segment, but that will have already been restored for whatever
 	 * we're returning to (such as userspace): we can't trust it.  The %ss:
 	 * prefix makes sure we use the stack segment, which is still valid.
 	 */
-	movl	%eax,%ss:lguest_data+LGUEST_DATA_irq_enabled
-	popl	%eax
+	popl	%ss:lguest_data+LGUEST_DATA_irq_enabled
+lguest_noirq_iret:
 	iret
-lguest_noirq_end: