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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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arch/x86/xen/enlighten.c
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@@ -1089,7 +1089,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = {
.read_pmc = native_read_pmc,
.iret = xen_iret,
.irq_enable_syscall_ret = xen_sysexit,
.irq_enable_sysexit = xen_sysexit,
.load_tr_desc = paravirt_nop,
.set_ldt = xen_set_ldt,