Re: [PATCH] vdpa: do not save failed dma maps in SVQ iova tree

[Eugenio Perez Martin]

On Thu, Aug 4, 2022 at 6:51 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2022/8/3 16:12, Eugenio Perez Martin 写道:
> > On Wed, Aug 3, 2022 at 10:09 AM Jason Wang <jasowang@redhat.com> wrote:
> >> On Tue, Aug 2, 2022 at 10:39 PM Eugenio Pérez <eperezma@redhat.com> wrote:
> >>> If a map fails for whatever reason, it must not be saved in the tree.
> >>> Otherwise, qemu will try to unmap it in cleanup, leaving to more errors.
> >>>
> >>> Fixes: 34e3c94eda ("vdpa: Add custom IOTLB translations to SVQ")
> >>> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> >>> ---
> >>>   hw/virtio/vhost-vdpa.c | 20 +++++++++++++-------
> >>>   1 file changed, 13 insertions(+), 7 deletions(-)
> >>>
> >>> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> >>> index 3ff9ce3501..e44c23dce5 100644
> >>> --- a/hw/virtio/vhost-vdpa.c
> >>> +++ b/hw/virtio/vhost-vdpa.c
> >>> @@ -176,6 +176,7 @@ static void vhost_vdpa_listener_commit(MemoryListener 
> >>> *listener)
> >>>   static void vhost_vdpa_listener_region_add(MemoryListener *listener,
> >>>                                              MemoryRegionSection *section)
> >>>   {
> >>> +    DMAMap mem_region = {};
> >>>       struct vhost_vdpa *v = container_of(listener, struct vhost_vdpa, 
> >>> listener);
> >>>       hwaddr iova;
> >>>       Int128 llend, llsize;
> >>> @@ -212,13 +213,13 @@ static void 
> >>> vhost_vdpa_listener_region_add(MemoryListener *listener,
> >>>
> >>>       llsize = int128_sub(llend, int128_make64(iova));
> >>>       if (v->shadow_vqs_enabled) {
> >>> -        DMAMap mem_region = {
> >>> -            .translated_addr = (hwaddr)(uintptr_t)vaddr,
> >>> -            .size = int128_get64(llsize) - 1,
> >>> -            .perm = IOMMU_ACCESS_FLAG(true, section->readonly),
> >>> -        };
> >> Nit: can we keep this part unchanged?
> >>
> > We can, but that implies we should look for iova again at fail_map
> > tag. If you are ok with that I'm fine to perform the search again.
>
>
> I meant something like:
>
> diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> index 9a2daef7e3..edf40868e3 100644
> --- a/hw/virtio/vhost-vdpa.c
> +++ b/hw/virtio/vhost-vdpa.c
> @@ -232,11 +232,15 @@ static void
> vhost_vdpa_listener_region_add(MemoryListener *listener,
>                                vaddr, section->readonly);
>       if (ret) {
>           error_report("vhost vdpa map fail!");
> -        goto fail;
> +        goto fail_unmap;
>       }
>
>       return;
>
> +fail_unmap:
> +    if (v->shadow_vqs_enabled) {
> +        vhost_iova_tree_remove(v->iova_tree, &mem_region);
> +    }
>   fail:
>       /*
>        * On the initfn path, store the first error in the container so we
>

Sorry, still not following.

mem_region does not exist in the error path, since it's declared in
the if (v->shadow_vqs_enabled){} block. We can left first part
unchanged if we do a lookup for the mem region, based on the
translated addr.

Thanks!

> Thanks
>
>
> >
> >> Thanks
> >>
> >>> +        int r;
> >>>
> >>> -        int r = vhost_iova_tree_map_alloc(v->iova_tree, &mem_region);
> >>> +        mem_region.translated_addr = (hwaddr)(uintptr_t)vaddr,
> >>> +        mem_region.size = int128_get64(llsize) - 1,
> >>> +        mem_region.perm = IOMMU_ACCESS_FLAG(true, section->readonly),
> >>> +
> >>> +        r = vhost_iova_tree_map_alloc(v->iova_tree, &mem_region);
> >>>           if (unlikely(r != IOVA_OK)) {
> >>>               error_report("Can't allocate a mapping (%d)", r);
> >>>               goto fail;
> >>> @@ -232,11 +233,16 @@ static void 
> >>> vhost_vdpa_listener_region_add(MemoryListener *listener,
> >>>                                vaddr, section->readonly);
> >>>       if (ret) {
> >>>           error_report("vhost vdpa map fail!");
> >>> -        goto fail;
> >>> +        goto fail_map;
> >>>       }
> >>>
> >>>       return;
> >>>
> >>> +fail_map:
> >>> +    if (v->shadow_vqs_enabled) {
> >>> +        vhost_iova_tree_remove(v->iova_tree, &mem_region);
> >>> +    }
> >>> +
> >>>   fail:
> >>>       /*
> >>>        * On the initfn path, store the first error in the container so we
> >>> --
> >>> 2.31.1
> >>>
>