Re: [PATCH v3] vhost/vdpa: Add MSI translation tables to iommu for software-managed MSI

[Jason Wang]

On Thu, Mar 21, 2024 at 3:00 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Wed, Mar 20, 2024 at 06:19:12PM +0800, Wang Rong wrote:
> > From: Rong Wang <w_angrong@xxxxxxx>
> >
> > Once enable iommu domain for one device, the MSI
> > translation tables have to be there for software-managed MSI.
> > Otherwise, platform with software-managed MSI without an
> > irq bypass function, can not get a correct memory write event
> > from pcie, will not get irqs.
> > The solution is to obtain the MSI phy base address from
> > iommu reserved region, and set it to iommu MSI cookie,
> > then translation tables will be created while request irq.
> >
> > Change log
> > ----------
> >
> > v1->v2:
> > - add resv iotlb to avoid overlap mapping.
> > v2->v3:
> > - there is no need to export the iommu symbol anymore.
> >
> > Signed-off-by: Rong Wang <w_angrong@xxxxxxx>
>
> There's in interest to keep extending vhost iotlb -
> we should just switch over to iommufd which supports
> this already.

IOMMUFD is good but VFIO supports this before IOMMUFD. This patch
makes vDPA run without a backporting of full IOMMUFD in the production
environment. I think it's worth.

If you worry about the extension, we can just use the vhost iotlb
existing facility to do this.

Thanks

>
> > ---
> >  drivers/vhost/vdpa.c | 59 +++++++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 56 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > index ba52d128aeb7..28b56b10372b 100644
> > --- a/drivers/vhost/vdpa.c
> > +++ b/drivers/vhost/vdpa.c
> > @@ -49,6 +49,7 @@ struct vhost_vdpa {
> >       struct completion completion;
> >       struct vdpa_device *vdpa;
> >       struct hlist_head as[VHOST_VDPA_IOTLB_BUCKETS];
> > +     struct vhost_iotlb resv_iotlb;
> >       struct device dev;
> >       struct cdev cdev;
> >       atomic_t opened;
> > @@ -247,6 +248,7 @@ static int _compat_vdpa_reset(struct vhost_vdpa *v)
> >  static int vhost_vdpa_reset(struct vhost_vdpa *v)
> >  {
> >       v->in_batch = 0;
> > +     vhost_iotlb_reset(&v->resv_iotlb);
> >       return _compat_vdpa_reset(v);
> >  }
> >
> > @@ -1219,10 +1221,15 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
> >           msg->iova + msg->size - 1 > v->range.last)
> >               return -EINVAL;
> >
> > +     if (vhost_iotlb_itree_first(&v->resv_iotlb, msg->iova,
> > +                                     msg->iova + msg->size - 1))
> > +             return -EINVAL;
> > +
> >       if (vhost_iotlb_itree_first(iotlb, msg->iova,
> >                                   msg->iova + msg->size - 1))
> >               return -EEXIST;
> >
> > +
> >       if (vdpa->use_va)
> >               return vhost_vdpa_va_map(v, iotlb, msg->iova, msg->size,
> >                                        msg->uaddr, msg->perm);
> > @@ -1307,6 +1314,45 @@ static ssize_t vhost_vdpa_chr_write_iter(struct kiocb *iocb,
> >       return vhost_chr_write_iter(dev, from);
> >  }
> >
> > +static int vhost_vdpa_resv_iommu_region(struct iommu_domain *domain, struct device *dma_dev,
> > +     struct vhost_iotlb *resv_iotlb)
> > +{
> > +     struct list_head dev_resv_regions;
> > +     phys_addr_t resv_msi_base = 0;
> > +     struct iommu_resv_region *region;
> > +     int ret = 0;
> > +     bool with_sw_msi = false;
> > +     bool with_hw_msi = false;
> > +
> > +     INIT_LIST_HEAD(&dev_resv_regions);
> > +     iommu_get_resv_regions(dma_dev, &dev_resv_regions);
> > +
> > +     list_for_each_entry(region, &dev_resv_regions, list) {
> > +             ret = vhost_iotlb_add_range_ctx(resv_iotlb, region->start,
> > +                             region->start + region->length - 1,
> > +                             0, 0, NULL);
> > +             if (ret) {
> > +                     vhost_iotlb_reset(resv_iotlb);
> > +                     break;
> > +             }
> > +
> > +             if (region->type == IOMMU_RESV_MSI)
> > +                     with_hw_msi = true;
> > +
> > +             if (region->type == IOMMU_RESV_SW_MSI) {
> > +                     resv_msi_base = region->start;
> > +                     with_sw_msi = true;
> > +             }
> > +     }
> > +
> > +     if (!ret && !with_hw_msi && with_sw_msi)
> > +             ret = iommu_get_msi_cookie(domain, resv_msi_base);
> > +
> > +     iommu_put_resv_regions(dma_dev, &dev_resv_regions);
> > +
> > +     return ret;
> > +}
> > +
> >  static int vhost_vdpa_alloc_domain(struct vhost_vdpa *v)
> >  {
> >       struct vdpa_device *vdpa = v->vdpa;
> > @@ -1335,11 +1381,16 @@ static int vhost_vdpa_alloc_domain(struct vhost_vdpa *v)
> >
> >       ret = iommu_attach_device(v->domain, dma_dev);
> >       if (ret)
> > -             goto err_attach;
> > +             goto err_alloc_domain;
> >
> > -     return 0;
> > +     ret = vhost_vdpa_resv_iommu_region(v->domain, dma_dev, &v->resv_iotlb);
> > +     if (ret)
> > +             goto err_attach_device;
> >
> > -err_attach:
> > +     return 0;
> > +err_attach_device:
> > +     iommu_detach_device(v->domain, dma_dev);
> > +err_alloc_domain:
> >       iommu_domain_free(v->domain);
> >       v->domain = NULL;
> >       return ret;
> > @@ -1595,6 +1646,8 @@ static int vhost_vdpa_probe(struct vdpa_device *vdpa)
> >               goto err;
> >       }
> >
> > +     vhost_iotlb_init(&v->resv_iotlb, 0, 0);
> > +
> >       r = dev_set_name(&v->dev, "vhost-vdpa-%u", minor);
> >       if (r)
> >               goto err;
> > --
> > 2.27.0
> >
>