Messages in this thread | | | Date | Thu, 19 Nov 2015 09:18:08 +0100 | From | Martin Schwidefsky <> | Subject | Re: [PATCH 2/2] s390/mm: allow gmap code to retry on faulting in guest memory |
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On Thu, 19 Nov 2015 00:49:58 +0100 Dominik Dingel <dingel@linux.vnet.ibm.com> wrote:
> The userfaultfd does need FAULT_FLAG_ALLOW_RETRY to not return > VM_FAULT_SIGBUS. So we improve the gmap code to handle one > VM_FAULT_RETRY. > > Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com> > --- > arch/s390/mm/pgtable.c | 28 ++++++++++++++++++++++++---- > 1 file changed, 24 insertions(+), 4 deletions(-) > > diff --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c > index 54ef3bc..8a0025d 100644 > --- a/arch/s390/mm/pgtable.c > +++ b/arch/s390/mm/pgtable.c > @@ -577,15 +577,22 @@ int gmap_fault(struct gmap *gmap, unsigned long gaddr, > unsigned int fault_flags) > { > unsigned long vmaddr; > - int rc; > + int rc, fault; > > + fault_flags |= FAULT_FLAG_ALLOW_RETRY; > +retry: > down_read(&gmap->mm->mmap_sem); > vmaddr = __gmap_translate(gmap, gaddr); > if (IS_ERR_VALUE(vmaddr)) { > rc = vmaddr; > goto out_up; > } > - if (fixup_user_fault(current, gmap->mm, vmaddr, fault_flags)) { > + fault = fixup_user_fault(current, gmap->mm, vmaddr, fault_flags); > + if (fault & VM_FAULT_RETRY) { > + fault_flags &= ~FAULT_FLAG_ALLOW_RETRY; > + fault_flags |= FAULT_FLAG_TRIED; > + goto retry; > + } else if (fault) { > rc = -EFAULT; > goto out_up; > }
Me thinks that you want to add the retry code into fixup_user_fault itself. You basically have the same code around the three calls to fixup_user_fault. Yes, it will be a common code patch but I guess that it will be acceptable given userfaultfd as a reason.
-- blue skies, Martin.
"Reality continues to ruin my life." - Calvin.
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