diff options
| author | Jeremy Fitzhardinge <jeremy@goop.org> | 2008-04-02 19:54:11 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-04-24 23:57:33 +0200 |
| commit | b77797fb2bf31bf076e6b69736119bc6a077525b (patch) | |
| tree | 4d0bfcb5bcc96988ef421c807837d7236fdb0e07 /arch/x86/xen | |
| parent | xen: allow set_pte_at on init_mm to be lockless (diff) | |
| download | linux-b77797fb2bf31bf076e6b69736119bc6a077525b.tar.xz linux-b77797fb2bf31bf076e6b69736119bc6a077525b.zip | |
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: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/xen')
| -rw-r--r-- | arch/x86/xen/xen-asm.S | 70 |
1 files changed, 14 insertions, 56 deletions
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S index 53cae923e148..2497a30f41de 100644 --- a/arch/x86/xen/xen-asm.S +++ b/arch/x86/xen/xen-asm.S @@ -108,6 +108,20 @@ ENDPATCH(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 4: cs @@ -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. |