x86/vIRQ: IRR and TMR race condition bug fix

x86/vIRQ: IRR and TMR race condition bug fix

In vlapic_set_irq, we set the IRR register before the TMR. And the IRR
might be serviced before setting TMR, and even worse EOI might occur
before TMR setting, in which case the vioapic_update_EOI won't be
called, and further prevent all the subsequent interrupt injecting.
Reorder setting the TMR and IRR will solve the problem.

Besides, KVM has fixed a similar bug in:
http://markmail.org/search/?q=APIC_TMR#query:APIC_TMR+page:1+mid:rphs4f7lkxjlldne+state:results

Signed-off-by: Yongan Liu<Liuyongan@huawei.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Committed-by: Jan Beulich <jbeulich@suse.com>
xen-unstable changeset:   24453:02b92d035f64
xen-unstable date:        Thu Jan 05 09:29:59 2012 +0100