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>

1 files changed, 9 insertions, 3 deletions

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 78c9a1b9e6b0..565ee7a990ea 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -140,7 +140,8 @@ unsigned paravirt_patch_default(u8 type, u16 clobbers, void *insnbuf,
                 /* If the operation is a nop, then nop the callsite */
                 ret = paravirt_patch_nop();
         else if (type == PARAVIRT_PATCH(pv_cpu_ops.iret) ||
-                 type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_syscall_ret))
+                 type == PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit) ||
+                 type == PARAVIRT_PATCH(pv_cpu_ops.usersp_sysret))
                 /* If operation requires a jmp, then jmp */
                 ret = paravirt_patch_jmp(insnbuf, opfunc, addr, len);
         else
@@ -191,7 +192,8 @@ static void native_flush_tlb_single(unsigned long addr)
 
 /* These are in entry.S */
 extern void native_iret(void);
-extern void native_irq_enable_syscall_ret(void);
+extern void native_irq_enable_sysexit(void);
+extern void native_usersp_sysret(void);
 
 static int __init print_banner(void)
 {
@@ -327,7 +329,11 @@ struct pv_cpu_ops pv_cpu_ops = {
         .write_idt_entry = native_write_idt_entry,
         .load_sp0 = native_load_sp0,
 
-        .irq_enable_syscall_ret = native_irq_enable_syscall_ret,
+#ifdef CONFIG_X86_32
+        .irq_enable_sysexit = native_irq_enable_sysexit,
+#else
+        .usersp_sysret = native_usersp_sysret,
+#endif
         .iret = native_iret,
         .swapgs = native_swapgs,