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xen: support sysenter/sysexit if hypervisor does

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64-bit Xen supports sysenter for 32-bit guests, so support its
use.  (sysenter is faster than int $0x80 in 32-on-64.)

sysexit is still not supported, so we fake it up using iret.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Jeremy Fitzhardinge
2008-03-17 16:37:17 -07:00
committed by Ingo Molnar
parent aa380c82b8
commit e2a81baf66
6 changed files with 99 additions and 3 deletions
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3
arch/x86/xen/enlighten.c
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@@ -155,7 +155,6 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
if (*ax == 1)
maskedx = ~((1 << X86_FEATURE_APIC) | /* disable APIC */
(1 << X86_FEATURE_ACPI) | /* disable ACPI */
(1 << X86_FEATURE_SEP) | /* disable SEP */
(1 << X86_FEATURE_ACC)); /* thermal monitoring */
asm(XEN_EMULATE_PREFIX "cpuid"
@@ -994,7 +993,7 @@ static const struct pv_cpu_ops xen_cpu_ops __initdata = {
.read_pmc = native_read_pmc,
.iret = xen_iret,
.irq_enable_syscall_ret = NULL, /* never called */
.irq_enable_syscall_ret = xen_sysexit,
.load_tr_desc = paravirt_nop,
.set_ldt = xen_set_ldt,