Re: [Qemu-devel] [PATCH v5] memory: do not notify for non inclusive overlap entry

[Yan Zhao]

On Mon, Jul 01, 2019 at 06:10:33PM +0800, Auger Eric wrote:
> Hi Yan,
> 
> On 6/29/19 12:19 AM, Yan Zhao wrote:
> > if an entry has non inclusive overlap with the notifier, print warning
> > message and do not do notification for it.
> > 
> > Out of scope mapping/unmapping would cause problem, as in below case:
> > 
> > 1. initially there are two notifiers with ranges
> > 0-0xfedfffff, 0xfef00000-0xffffffffffffffff,
> > IOVAs from 0x3c000000 - 0x3c1fffff is in shadow page table.
> > 
> > 2. in vfio, memory_region_register_iommu_notifier() is followed by
> > memory_region_iommu_replay(), which will first call address space
> > unmap,
> > and walk and add back all entries in vtd shadow page table. e.g.
> > (1) for notifier 0-0xfedfffff,
> >     IOVAs from 0 - 0xffffffff get unmapped,
> >     and IOVAs from 0x3c000000 - 0x3c1fffff get mapped
> > (2) for notifier 0xfef00000-0xffffffffffffffff
> >     IOVAs from 0 - 0x7fffffffff get unmapped,
> >     but IOVAs from 0x3c000000 - 0x3c1fffff cannot get mapped back.
> > 
> > Cc: Eric Auger <address@hidden>
> > Cc: Peter Xu <address@hidden>
> > Signed-off-by: Yan Zhao <address@hidden>
> Reviewed-by: Eric Auger <address@hidden>
> 
> Thanks
> 
> Eric

Thank you, Eric :)

Yan
> > 
> > ---
> > v5:
> > 1. still using warn_report instead of "assert"
> > 2. returning at the end to refuse notification for entry which has non
> > inclusive overlap with the notifier.
> > 3. updated commit title and warning message.
> > 
> > v4:
> > 1. modified commit title
> > 2. using "assert" instead of printing warning message
> > 
> > v3:
> > refined code style and message format
> > 
> > v2:
> > 1. added a local variable entry_end (Eric Auger)
> > 2. using PRIx64 as format for address range in warning message
> > (Eric Auger)
> > ---
> >  memory.c | 16 ++++++++++++++--
> >  1 file changed, 14 insertions(+), 2 deletions(-)
> > 
> > diff --git a/memory.c b/memory.c
> > index 0a089a7..fe0d08d 100644
> > --- a/memory.c
> > +++ b/memory.c
> > @@ -1937,13 +1937,13 @@ void memory_region_notify_one(IOMMUNotifier 
> > *notifier,
> >                                IOMMUTLBEntry *entry)
> >  {
> >      IOMMUNotifierFlag request_flags;
> > +    hwaddr entry_end = entry->iova + entry->addr_mask;
> >  
> >      /*
> >       * Skip the notification if the notification does not overlap
> >       * with registered range.
> >       */
> > -    if (notifier->start > entry->iova + entry->addr_mask ||
> > -        notifier->end < entry->iova) {
> > +    if (notifier->start > entry_end || notifier->end < entry->iova) {
> >          return;
> >      }
> >  
> > @@ -1953,6 +1953,18 @@ void memory_region_notify_one(IOMMUNotifier 
> > *notifier,
> >          request_flags = IOMMU_NOTIFIER_UNMAP;
> >      }
> >  
> > +    if (entry->iova < notifier->start || entry_end > notifier->end) {
> > +        warn_report("IOMMUTLBEntry 0x%" PRIx64 " - 0x%" PRIx64
> > +                " has non inclusive overlap with notifier 0x%" PRIx64
> > +                " - 0x%" PRIx64 ". %s is not allowed."
> > +                " Try to divide it into smaller sections.",
> > +                entry->iova, entry_end,
> > +                notifier->start, notifier->end,
> > +                (request_flags == IOMMU_NOTIFIER_MAP) ?
> > +                "Mapping" : "Unmapping");
> > +        return;
> > +    }
> > +
> >      if (notifier->notifier_flags & request_flags) {
> >          notifier->notify(notifier, entry);
> >      }
> >