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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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21
arch/x86/xen/setup.c
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@ -16,6 +16,7 @@
#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>
#include <xen/interface/callback.h>
#include <xen/interface/physdev.h>
#include <xen/features.h>
@ -68,6 +69,24 @@ static void __init fiddle_vdso(void)
*mask |= 1 << VDSO_NOTE_NONEGSEG_BIT;
}
void xen_enable_sysenter(void)
{
int cpu = smp_processor_id();
extern void xen_sysenter_target(void);
/* Mask events on entry, even though they get enabled immediately */
static struct callback_register sysenter = {
.type = CALLBACKTYPE_sysenter,
.address = { __KERNEL_CS, (unsigned long)xen_sysenter_target },
.flags = CALLBACKF_mask_events,
};
if (!boot_cpu_has(X86_FEATURE_SEP) ||
HYPERVISOR_callback_op(CALLBACKOP_register, &sysenter) != 0) {
clear_cpu_cap(&cpu_data(cpu), X86_FEATURE_SEP);
clear_cpu_cap(&boot_cpu_data, X86_FEATURE_SEP);
}
}
void __init xen_arch_setup(void)
{
struct physdev_set_iopl set_iopl;
@ -82,6 +101,8 @@ void __init xen_arch_setup(void)
HYPERVISOR_set_callbacks(__KERNEL_CS, (unsigned long)xen_hypervisor_callback,
__KERNEL_CS, (unsigned long)xen_failsafe_callback);
xen_enable_sysenter();
set_iopl.iopl = 1;
rc = HYPERVISOR_physdev_op(PHYSDEVOP_set_iopl, &set_iopl);
if (rc != 0)