Commit b77797fb authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge Committed by Ingo Molnar
Browse files

xen: fold xen_sysexit into xen_iret 



xen_sysexit and xen_iret were doing essentially the same thing.  Rather
than having a separate implementation for xen_sysexit, we can just strip
the stack back to an iret frame and jump into xen_iret.  This removes
a lot of code and complexity - specifically, another critical region.

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 2bd50036

arch/x86/kernel/entry_32.S

+1 −8
Original line number Diff line number Diff line
@@ -1044,15 +1044,8 @@ ENTRY(xen_hypervisor_callback) 


	jmp  xen_iret_crit_fixup



1:	cmpl $xen_sysexit_start_crit,%eax

	jb   2f

	cmpl $xen_sysexit_end_crit,%eax

	jae  2f



	jmp xen_sysexit_crit_fixup



ENTRY(xen_do_upcall)

2:	mov %esp, %eax

1:	mov %esp, %eax

	call xen_evtchn_do_upcall

	jmp  ret_from_intr

	CFI_ENDPROC

arch/x86/xen/xen-asm.S

+14 −56
Original line number Diff line number Diff line
@@ -107,6 +107,20 @@ ENDPATCH(xen_restore_fl_direct) 
	ENDPROC(xen_restore_fl_direct)

	RELOC(xen_restore_fl_direct, 2b+1)



/*

	We can't use sysexit directly, because we're not running in ring0.

	But we can easily fake it up using iret.  Assuming xen_sysexit

	is jumped to with a standard stack frame, we can just strip it

	back to a standard iret frame and use iret.

 */

ENTRY(xen_sysexit)

	movl PT_EAX(%esp), %eax			/* Shouldn't be necessary? */

	orl $X86_EFLAGS_IF, PT_EFLAGS(%esp)

	lea PT_EIP(%esp), %esp



	jmp xen_iret

ENDPROC(xen_sysexit)



/*

	This is run where a normal iret would be run, with the same stack setup:

	      8: eflags
@@ -276,62 +290,6 @@ ENTRY(xen_iret_crit_fixup) 
2:	jmp xen_do_upcall





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.

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