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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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4
arch/x86/kernel/vmi_32.c
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@@ -151,7 +151,7 @@ static unsigned vmi_patch(u8 type, u16 clobbers, void *insns,
insns, ip);
case PARAVIRT_PATCH(pv_cpu_ops.iret):
return patch_internal(VMI_CALL_IRET, len, insns, ip);
case PARAVIRT_PATCH(pv_cpu_ops.irq_enable_syscall_ret):
case PARAVIRT_PATCH(pv_cpu_ops.irq_enable_sysexit):
return patch_internal(VMI_CALL_SYSEXIT, len, insns, ip);
default:
break;
@@ -896,7 +896,7 @@ static inline int __init activate_vmi(void)
* the backend. They are performance critical anyway, so requiring
* a patch is not a big problem.
*/
pv_cpu_ops.irq_enable_syscall_ret = (void *)0xfeedbab0;
pv_cpu_ops.irq_enable_sysexit = (void *)0xfeedbab0;
pv_cpu_ops.iret = (void *)0xbadbab0;
#ifdef CONFIG_SMP