On Tue, 16 Jul 2013 10:04:18 -0400 Vivek Goyal <vgoyal at redhat.com> wrote: > On Tue, Jul 16, 2013 at 11:25:27AM +0200, Michael Holzheu wrote: > > [..] > > > > Hello Vivek and Andrew, > > > > > > > > We just realized that Hatayama's mmap patches went into v3.11-rc1. This currently > > > > breaks s390 kdump because of the following two issues: > > > > > > > > 1) The copy_oldmem_page() is now used for copying to vmalloc memory > > > > 2) The mmap() implementation is not compatible with the current > > > > s390 crashkernel swap: > > > > See: http://marc.info/?l=kexec&m=136940802511603&w=2 > > > > > > > > The "kdump: Introduce ELF header in new memory feature" patch series will > > > > fix both issues for s390. > > > > > > > > There is the one small open discussion left: > > > > > > > > http://www.mail-archive.com/linux-kernel at vger.kernel.org/msg464856.html > > > > > > > > But once we have finished that, would it be possible to get the > > > > patches in 3.11? > > > > > > How about taking mmap() fault handler patches in 3.12. And in 3.11, deny > > > mmap() on s390 forcing makedumpfile to fall back on read() interface. That > > > way there will be no regression and mmap() related speedup will show up > > > in next release on s390. > > > > Hello Vivek and Hatayama, > > > > But then we still would have to somehow fix the copy_oldmem_page() issue (1). > > > > We would prefer to add the current patch series with "#ifndef CONFIG_S390" in > > the fault handler. > > > > @Vivek: > > > > Since you are the kdump maintainer, could you tell us which of the both > > variants you would like to have? > > > > static int mmap_vmcore_fault(struct vm_area_struct *vma, struct vm_fault *vmf) > > { > > ... > > > > #ifndef CONFIG_S390 > > return VM_FAULT_SIGBUS; > > #endif > > I think let us use this one. Kill the process on non-s390 arch if it goes > into mmap() fault handler. > > copy_oldmem_page() using real mode in s390 is an issue for vmalloc region. > I think post the series again and let us see if Andrew is comfortable > with it. Ok great, I will send Andrew the current patch series. Let's see what happens... > I suspect it is late. > IIUC, we do copying in real mode only to cope with HSA region in zfcpdump > case. The problem is that with the mmap patches we now use copy_oldmem_page() to copy the notes from oldmem into the notes_buf which has been allocated with vmalloc. The s390 version of copy_oldmem_page() bypasses the page tables and uses real copy. And this does not work on vmalloc memory. Best Regards, Michael
