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xen: x86_32: do not enable iterrupts when returning from exception in interrupt context

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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>
This commit is contained in:
Igor Mammedov 2011-09-01 13:46:55 +02:00 committed by Konrad Rzeszutek Wilk
parent d312ae878b
commit d198d49914
1 changed files with 5 additions and 3 deletions
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8
arch/x86/xen/xen-asm_32.S
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@ -113,11 +113,13 @@ xen_iret_start_crit:
/*
* If there's something pending, mask events again so we can
* jump back into xen_hypervisor_callback
* jump back into xen_hypervisor_callback. Otherwise do not
* touch XEN_vcpu_info_mask.
*/
sete XEN_vcpu_info_mask(%eax)
jne 1f
movb $1, XEN_vcpu_info_mask(%eax)
popl %eax
1: popl %eax
/*
* From this point on the registers are restored and the stack