[PATCH] paravirt: header and stubs for paravirtualisation

Create a paravirt.h header for all the critical operations which need to be
replaced with hypervisor calls, and include that instead of defining native
operations, when CONFIG_PARAVIRT.

This patch does the dumbest possible replacement of paravirtualized
instructions: calls through a "paravirt_ops" structure.  Currently these are
function implementations of native hardware: hypervisors will override the ops
structure with their own variants.

All the pv-ops functions are declared "fastcall" so that a specific
register-based ABI is used, to make inlining assember easier.

And:

+From: Andy Whitcroft <apw@shadowen.org>

The paravirt ops introduce a 'weak' attribute onto memory_setup().
Code ordering leads to the following warnings on x86:

    arch/i386/kernel/setup.c:651: warning: weak declaration of
                `memory_setup' after first use results in unspecified behavior

Move memory_setup() to avoid this.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andy Whitcroft <apw@shadowen.org>

1 files changed, 27 insertions, 7 deletions

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index 0220bc8cbb43..d274612e05cd 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -62,13 +62,6 @@ DF_MASK		= 0x00000400
 NT_MASK         = 0x00004000
 VM_MASK         = 0x00020000
 
-/* These are replaces for paravirtualization */
-#define DISABLE_INTERRUPTS              cli
-#define ENABLE_INTERRUPTS               sti
-#define ENABLE_INTERRUPTS_SYSEXIT       sti; sysexit
-#define INTERRUPT_RETURN                iret
-#define GET_CR0_INTO_EAX                movl %cr0, %eax
-
 #ifdef CONFIG_PREEMPT
 #define preempt_stop            DISABLE_INTERRUPTS; TRACE_IRQS_OFF
 #else
@@ -416,6 +409,20 @@ ldt_ss:
         jnz restore_nocheck
         testl $0x00400000, %eax         # returning to 32bit stack?
         jnz restore_nocheck             # allright, normal return
+
+#ifdef CONFIG_PARAVIRT
+        /*
+         * The kernel can't run on a non-flat stack if paravirt mode
+         * is active.  Rather than try to fixup the high bits of
+         * ESP, bypass this code entirely.  This may break DOSemu
+         * and/or Wine support in a paravirt VM, although the option
+         * is still available to implement the setting of the high
+         * 16-bits in the INTERRUPT_RETURN paravirt-op.
+         */
+        cmpl $0, paravirt_ops+PARAVIRT_enabled
+        jne restore_nocheck
+#endif
+
         /* If returning to userspace with 16bit stack,
          * try to fix the higher word of ESP, as the CPU
          * won't restore it.
@@ -833,6 +840,19 @@ nmi_espfix_stack:
 .previous
 KPROBE_END(nmi)
 
+#ifdef CONFIG_PARAVIRT
+ENTRY(native_iret)
+1:      iret
+.section __ex_table,"a"
+        .align 4
+        .long 1b,iret_exc
+.previous
+
+ENTRY(native_irq_enable_sysexit)
+        sti
+        sysexit
+#endif
+
 KPROBE_ENTRY(int3)
         RING0_INT_FRAME
         pushl $-1                       # mark this as an int