From: Igor Mammedov Date: Thu, 1 Sep 2011 11:46:55 +0000 (+0200) Subject: xen: x86_32: do not enable iterrupts when returning from exception in interrupt context X-Git-Tag: v2.6.34.13~137 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=51b5aa112c7c232dd85001a702c7ed82c1e7a394;p=karo-tx-linux.git xen: x86_32: do not enable iterrupts when returning from exception in interrupt context 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: Paul Gortmaker --- diff --git a/arch/x86/xen/xen-asm_32.S b/arch/x86/xen/xen-asm_32.S index 22a2093b5862..b040b0e518ca 100644 --- 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