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Commit e2a81baf authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
Browse files

xen: support sysenter/sysexit if hypervisor does 



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: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent aa380c82

arch/x86/kernel/entry_32.S

+17 −1
Original line number Diff line number Diff line
@@ -1017,6 +1017,13 @@ ENTRY(kernel_thread_helper) 
ENDPROC(kernel_thread_helper)



#ifdef CONFIG_XEN

/* Xen doesn't set %esp to be precisely what the normal sysenter

   entrypoint expects, so fix it up before using the normal path. */

ENTRY(xen_sysenter_target)

	RING0_INT_FRAME

	addl $5*4, %esp		/* remove xen-provided frame */

	jmp sysenter_past_esp



ENTRY(xen_hypervisor_callback)

	CFI_STARTPROC

	pushl $0
@@ -1036,8 +1043,17 @@ ENTRY(xen_hypervisor_callback) 
	jae  1f



	call xen_iret_crit_fixup

	jmp  2f



1:	cmpl $xen_sysexit_start_crit,%eax

	jb   2f

	cmpl $xen_sysexit_end_crit,%eax

	jae  2f



	jmp xen_sysexit_crit_fixup



1:	mov %esp, %eax

ENTRY(xen_do_upcall)

2:	mov %esp, %eax

	call xen_evtchn_do_upcall

	jmp  ret_from_intr

	CFI_ENDPROC

arch/x86/xen/enlighten.c

+1 −2
Original line number Diff line number Diff line
@@ -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,

arch/x86/xen/setup.c

+21 −0
Original line number Diff line number Diff line
@@ -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)

arch/x86/xen/smp.c

+1 −0
Original line number Diff line number Diff line
@@ -72,6 +72,7 @@ static __cpuinit void cpu_bringup_and_idle(void) 
	int cpu = smp_processor_id();



	cpu_init();

	xen_enable_sysenter();



	preempt_disable();

	per_cpu(cpu_state, cpu) = CPU_ONLINE;

arch/x86/xen/xen-asm.S

+56 −0
Original line number Diff line number Diff line
@@ -280,6 +280,62 @@ ENTRY(xen_iret_crit_fixup) 
2:	ret





ENTRY(xen_sysexit)

	/* Store vcpu_info pointer for easy access.  Do it this

	   way to avoid having to reload %fs */

#ifdef CONFIG_SMP

	GET_THREAD_INFO(%eax)

	movl TI_cpu(%eax),%eax

	movl __per_cpu_offset(,%eax,4),%eax

	mov per_cpu__xen_vcpu(%eax),%eax

#else

	movl per_cpu__xen_vcpu, %eax

#endif



	/* We can't actually use sysexit in a pv guest,

	   so fake it up with iret */

	pushl $__USER_DS		/* user stack segment */

	pushl %ecx			/* user esp */

	pushl PT_EFLAGS+2*4(%esp)	/* user eflags */

	pushl $__USER_CS		/* user code segment */

	pushl %edx			/* user eip */



xen_sysexit_start_crit:

	/* Unmask events... */

	movb $0, XEN_vcpu_info_mask(%eax)

	/* ...and test for pending.

	   There's a preempt window here, but it doesn't

	   matter because we're within the critical section. */

	testb $0xff, XEN_vcpu_info_pending(%eax)



	/* If there's something pending, mask events again so we

	   can directly inject it back into the kernel. */

	jnz   1f



	movl PT_EAX+5*4(%esp),%eax

2:	iret

1:	movb $1, XEN_vcpu_info_mask(%eax)

xen_sysexit_end_crit:

	addl $5*4, %esp		/* remove iret frame */

	/* no need to re-save regs, but need to restore kernel %fs */

	mov $__KERNEL_PERCPU, %eax

	mov %eax, %fs

	jmp xen_do_upcall

.section __ex_table,"a"

	.align 4

	.long 2b,iret_exc

.previous



	.globl xen_sysexit_start_crit, xen_sysexit_end_crit

/*

	sysexit fixup is easy, since the old frame is still sitting there

	on the stack.  We just need to remove the new recursive

	interrupt and return.

 */

ENTRY(xen_sysexit_crit_fixup)

	addl $PT_OLDESP+5*4, %esp		/* remove frame+iret */

	jmp xen_do_upcall



/*

	Force an event check by making a hypercall,

	but preserve regs before making the call.