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x86/paravirt: split sysret and sysexit

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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>
This commit is contained in:
Jeremy Fitzhardinge
2008-06-25 00:19:26 -04:00
committed by Ingo Molnar
parent e04e0a630d
commit d75cd22fdd
11 changed files with 36 additions and 25 deletions
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12
arch/x86/kernel/paravirt.c
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@@ -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,