Messages in this thread | | | Date | Fri, 02 Sep 2011 16:01:35 +0200 | From | Igor Mammedov <> | Subject | Re: [Xen-devel] Re: [PATCH v2] xen: x86_32: do not enable iterrupts when returning from exception in interrupt context |
| |
On 09/02/2011 03:40 PM, Konrad Rzeszutek Wilk wrote: > On Fri, Sep 02, 2011 at 10:18:23AM +0200, Igor Mammedov wrote: >> On 09/01/2011 06:46 PM, Jeremy Fitzhardinge wrote: >>> On 09/01/2011 04:46 AM, Igor Mammedov wrote: >>>> 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<imammedo@redhat.com> >>>> Signed-off-by: Jeremy Fitzhardinge<jeremy@goop.org> >>> >>> One nit, this should be acked-by or reviewed-by, not signed-off-by, >>> since the patch isn't passing through my hands. >>> >>> J >> >> I'm new to this stuff, would you like me to re-post it? > > That is OK. I fixed it up in the git commit. Thanks for finding this one!
You're welcome! I've learned a lot while debugging it. In particular, how to use kvm and qemu's gdbstub to debug xen and guest using gdb.
-- Thanks, Igor
| |