Re: [Qemu-devel] [PATCH v9 1/9] memory: add section range info for IOMMU notifier

[David Gibson <david@gibson.dropbear.id.au>]

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On Fri, Apr 07, 2017 at 06:59:07PM +0800, Peter Xu wrote:
> In this patch, IOMMUNotifier.{start|end} are introduced to store section
> information for a specific notifier. When notification occurs, we not
> only check the notification type (MAP|UNMAP), but also check whether the
> notified iova range overlaps with the range of specific IOMMU notifier,
> and skip those notifiers if not in the listened range.
> 
> When removing an region, we need to make sure we removed the correct
> VFIOGuestIOMMU by checking the IOMMUNotifier.start address as well.
> 
> This patch is solving the problem that vfio-pci devices receive
> duplicated UNMAP notification on x86 platform when vIOMMU is there. The
> issue is that x86 IOMMU has a (0, 2^64-1) IOMMU region, which is
> splitted by the (0xfee00000, 0xfeefffff) IRQ region. AFAIK
> this (splitted IOMMU region) is only happening on x86.
> 
> This patch also helps vhost to leverage the new interface as well, so
> that vhost won't get duplicated cache flushes. In that sense, it's an
> slight performance improvement.
> 
> Suggested-by: David Gibson <david@gibson.dropbear.id.au>
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Acked-by: Alex Williamson <alex.williamson@redhat.com>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  hw/vfio/common.c      | 12 +++++++++---
>  hw/virtio/vhost.c     | 10 ++++++++--
>  include/exec/memory.h | 19 ++++++++++++++++++-
>  memory.c              |  9 +++++++++
>  4 files changed, 44 insertions(+), 6 deletions(-)
> 
> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> index f3ba9b9..6b33b9f 100644
> --- a/hw/vfio/common.c
> +++ b/hw/vfio/common.c
> @@ -478,8 +478,13 @@ static void vfio_listener_region_add(MemoryListener *listener,
>          giommu->iommu_offset = section->offset_within_address_space -
>                                 section->offset_within_region;
>          giommu->container = container;
> -        giommu->n.notify = vfio_iommu_map_notify;
> -        giommu->n.notifier_flags = IOMMU_NOTIFIER_ALL;
> +        llend = int128_add(int128_make64(section->offset_within_region),
> +                           section->size);
> +        llend = int128_sub(llend, int128_one());
> +        iommu_notifier_init(&giommu->n, vfio_iommu_map_notify,
> +                            IOMMU_NOTIFIER_ALL,
> +                            section->offset_within_region,
> +                            int128_get64(llend));

Seems to me it would make sense to put the fiddling around to convert
the MemoryRegionSection into the necessary values would make sense to
go inside iommu_notifier_init().

>          QLIST_INSERT_HEAD(&container->giommu_list, giommu, giommu_next);
>  
>          memory_region_register_iommu_notifier(giommu->iommu, &giommu->n);
> @@ -550,7 +555,8 @@ static void vfio_listener_region_del(MemoryListener *listener,
>          VFIOGuestIOMMU *giommu;
>  
>          QLIST_FOREACH(giommu, &container->giommu_list, giommu_next) {
> -            if (giommu->iommu == section->mr) {
> +            if (giommu->iommu == section->mr &&
> +                giommu->n.start == section->offset_within_region) {

This test should be sufficient, but I'd be a bit more comfortable if
there was a test and assert() that the end matches as well.  I also
wonder if remove-matching-notifier helper would be useful here.
Although vhost doesn't appear to ever remove, so maybe it's premature.

>                  memory_region_unregister_iommu_notifier(giommu->iommu,
>                                                          &giommu->n);
>                  QLIST_REMOVE(giommu, giommu_next);
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 613494d..185b95b 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -736,14 +736,20 @@ static void vhost_iommu_region_add(MemoryListener *listener,
>      struct vhost_dev *dev = container_of(listener, struct vhost_dev,
>                                           iommu_listener);
>      struct vhost_iommu *iommu;
> +    Int128 end;
>  
>      if (!memory_region_is_iommu(section->mr)) {
>          return;
>      }
>  
>      iommu = g_malloc0(sizeof(*iommu));
> -    iommu->n.notify = vhost_iommu_unmap_notify;
> -    iommu->n.notifier_flags = IOMMU_NOTIFIER_UNMAP;
> +    end = int128_add(int128_make64(section->offset_within_region),
> +                     section->size);
> +    end = int128_sub(end, int128_one());
> +    iommu_notifier_init(&iommu->n, vhost_iommu_unmap_notify,
> +                        IOMMU_NOTIFIER_UNMAP,
> +                        section->offset_within_region,
> +                        int128_get64(end));
>      iommu->mr = section->mr;
>      iommu->iommu_offset = section->offset_within_address_space -
>                            section->offset_within_region;
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index f20b191..0840c89 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -77,13 +77,30 @@ typedef enum {
>  
>  #define IOMMU_NOTIFIER_ALL (IOMMU_NOTIFIER_MAP | IOMMU_NOTIFIER_UNMAP)
>  
> +struct IOMMUNotifier;
> +typedef void (*IOMMUNotify)(struct IOMMUNotifier *notifier,
> +                            IOMMUTLBEntry *data);
> +
>  struct IOMMUNotifier {
> -    void (*notify)(struct IOMMUNotifier *notifier, IOMMUTLBEntry *data);
> +    IOMMUNotify notify;
>      IOMMUNotifierFlag notifier_flags;
> +    /* Notify for address space range start <= addr <= end */
> +    hwaddr start;
> +    hwaddr end;
>      QLIST_ENTRY(IOMMUNotifier) node;
>  };
>  typedef struct IOMMUNotifier IOMMUNotifier;
>  
> +static inline void iommu_notifier_init(IOMMUNotifier *n, IOMMUNotify fn,
> +                                       IOMMUNotifierFlag flags,
> +                                       hwaddr start, hwaddr end)
> +{
> +    n->notify = fn;
> +    n->notifier_flags = flags;
> +    n->start = start;
> +    n->end = end;
> +}
> +
>  /* New-style MMIO accessors can indicate that the transaction failed.
>   * A zero (MEMTX_OK) response means success; anything else is a failure
>   * of some kind. The memory subsystem will bitwise-OR together results
> diff --git a/memory.c b/memory.c
> index 4c95aaf..75ac595 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -1606,6 +1606,7 @@ void memory_region_register_iommu_notifier(MemoryRegion *mr,
>  
>      /* We need to register for at least one bitfield */
>      assert(n->notifier_flags != IOMMU_NOTIFIER_NONE);
> +    assert(n->start <= n->end);
>      QLIST_INSERT_HEAD(&mr->iommu_notify, n, node);
>      memory_region_update_iommu_notify_flags(mr);
>  }
> @@ -1667,6 +1668,14 @@ void memory_region_notify_iommu(MemoryRegion *mr,
>      }
>  
>      QLIST_FOREACH(iommu_notifier, &mr->iommu_notify, node) {
> +        /*
> +         * Skip the notification if the notification does not overlap
> +         * with registered range.
> +         */
> +        if (iommu_notifier->start > entry.iova + entry.addr_mask + 1 ||
> +            iommu_notifier->end < entry.iova) {
> +            continue;
> +        }
>          if (iommu_notifier->notifier_flags & request_flags) {
>              iommu_notifier->notify(iommu_notifier, &entry);
>          }

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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