xen: x86_32: do not enable iterrupts when returning from exception in interrupt context
authorIgor Mammedov <imammedo@redhat.com>
Thu, 1 Sep 2011 11:46:55 +0000 (13:46 +0200)
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Thu, 1 Sep 2011 16:54:42 +0000 (12:54 -0400)
commitd198d499148a0c64a41b3aba9e7dd43772832b91
treeddc0bf46ac10d84db5d06dceb44c21770692f596
parentd312ae878b6aed3912e1acaaf5d0b2a9d08a4f11
xen: x86_32: do not enable iterrupts when returning from exception in interrupt context

If vmalloc page_fault happens inside of interrupt handler with interrupts
disabled then on exit path from exception handler when there is no pending
interrupts, the following code (arch/x86/xen/xen-asm_32.S:112):

cmpw $0x0001, XEN_vcpu_info_pending(%eax)
sete XEN_vcpu_info_mask(%eax)

will enable interrupts even if they has been previously disabled according to
eflags from the bounce frame (arch/x86/xen/xen-asm_32.S:99)

testb $X86_EFLAGS_IF>>8, 8+1+ESP_OFFSET(%esp)
setz XEN_vcpu_info_mask(%eax)

Solution is in setting XEN_vcpu_info_mask only when it should be set
according to
cmpw $0x0001, XEN_vcpu_info_pending(%eax)
but not clearing it if there isn't any pending events.

Reproducer for bug is attached to RHBZ 707552

CC: stable@kernel.org
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
arch/x86/xen/xen-asm_32.S