blob: 499fd898b35d0f4ef22e22eff04861da4430b46d [file] [log] [blame]
From d198d499148a0c64a41b3aba9e7dd43772832b91 Mon Sep 17 00:00:00 2001
From: Igor Mammedov <>
Date: Thu, 1 Sep 2011 13:46:55 +0200
Subject: xen: x86_32: do not enable iterrupts when returning from exception in interrupt context
From: Igor Mammedov <>
commit d198d499148a0c64a41b3aba9e7dd43772832b91 upstream.
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
Signed-off-by: Igor Mammedov <>
Acked-by: Jeremy Fitzhardinge <>
Signed-off-by: Konrad Rzeszutek Wilk <>
Signed-off-by: Greg Kroah-Hartman <>
arch/x86/xen/xen-asm_32.S | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
--- a/arch/x86/xen/xen-asm_32.S
+++ b/arch/x86/xen/xen-asm_32.S
@@ -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