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

From: Jason Wang
Date: Sat Apr 06 2024 - 23:38:41 EST

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On Fri, Mar 29, 2024 at 6:42 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Fri, Mar 29, 2024 at 06:39:33PM +0800, Jason Wang wrote:
> > On Fri, Mar 29, 2024 at 5:13 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> > >
> > > On Wed, Mar 27, 2024 at 05:08:57PM +0800, Jason Wang wrote:
> > > > 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.
> > >
> > > You mean VFIO migrated to IOMMUFD but of course they keep supporting
> > > their old UAPI?
> >
> > I meant VFIO support software managed MSI before IOMMUFD.
>
> And then they switched over and stopped adding new IOMMU
> related features. And so should vdpa?

For some cloud vendors, it means vDPA can't be used until

1) IOMMUFD support for vDPA is supported by upstream
2) IOMMUFD is backported

1) might be fine but 2) might be impossible.

Assuming IOMMUFD hasn't been done for vDPA. Adding small features like
this seems reasonable (especially considering it is supported by the
"legacy" VFIO container).

Thanks

>
>
> > > OK and point being?
> > >
> > > > This patch
> > > > makes vDPA run without a backporting of full IOMMUFD in the production
> > > > environment. I think it's worth.
> > >
> > > Where do we stop? saying no to features is the only tool maintainers
> > > have to make cleanups happen, otherwise people will just keep piling
> > > stuff up.
> >
> > I think we should not have more features than VFIO without IOMMUFD.
> >
> > Thanks
> >
> > >
> > > > 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
> > > > > >
> > > > >
> > >
>

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