x86/paravirt: split sysret and sysexit
Don't conflate sysret and sysexit; they're different instructions with
different semantics, and may be in use at the same time (at least
within the same kernel, depending on whether its an Intel or AMD
system).
sysexit - just return to userspace, does no register restoration of
any kind; must explicitly atomically enable interrupts.
sysret - reloads flags from r11, so no need to explicitly enable
interrupts on 64-bit, responsible for restoring usermode %gs
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citirx.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 159a1c7..53393c3 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -58,7 +58,7 @@
* for paravirtualization. The following will never clobber any registers:
* INTERRUPT_RETURN (aka. "iret")
* GET_CR0_INTO_EAX (aka. "movl %cr0, %eax")
- * ENABLE_INTERRUPTS_SYSCALL_RET (aka "sti; sysexit").
+ * ENABLE_INTERRUPTS_SYSEXIT (aka "sti; sysexit").
*
* For DISABLE_INTERRUPTS/ENABLE_INTERRUPTS (aka "cli"/"sti"), you must
* specify what registers can be overwritten (CLBR_NONE, CLBR_EAX/EDX/ECX/ANY).
@@ -349,7 +349,7 @@
xorl %ebp,%ebp
TRACE_IRQS_ON
1: mov PT_FS(%esp), %fs
- ENABLE_INTERRUPTS_SYSCALL_RET
+ ENABLE_INTERRUPTS_SYSEXIT
CFI_ENDPROC
.pushsection .fixup,"ax"
2: movl $0,PT_FS(%esp)
@@ -874,10 +874,10 @@
.previous
END(native_iret)
-ENTRY(native_irq_enable_syscall_ret)
+ENTRY(native_irq_enable_sysexit)
sti
sysexit
-END(native_irq_enable_syscall_ret)
+END(native_irq_enable_sysexit)
#endif
KPROBE_ENTRY(int3)