On Wed, Jun 12, 2024 at 09:22:43AM +0000, Srujana Challa wrote: > > > Subject: Re: [EXTERNAL] Re: [PATCH] vdpa: Add support for no-IOMMU mode > > > > On Tue, Jun 4, 2024 at 5:29 PM Srujana Challa <schalla@xxxxxxxxxxx> wrote: > > > > > > > Subject: [EXTERNAL] Re: [PATCH] vdpa: Add support for no-IOMMU mode > > > > > > > > Prioritize security for external emails: Confirm sender and content > > > > safety before clicking links or opening attachments > > > > > > > > -------------------------------------------------------------------- > > > > -- On Thu, May 30, 2024 at 6:18 PM Srujana Challa > > > > <schalla@xxxxxxxxxxx> > > > > wrote: > > > > > > > > > > This commit introduces support for an UNSAFE, no-IOMMU mode in the > > > > > vhost-vdpa driver. When enabled, this mode provides no device > > > > > isolation, no DMA translation, no host kernel protection, and > > > > > cannot be used for device assignment to virtual machines. It > > > > > requires RAWIO permissions and will taint the kernel. > > > > > This mode requires enabling the > > > > "enable_vhost_vdpa_unsafe_noiommu_mode" > > > > > option on the vhost-vdpa driver. This mode would be useful to get > > > > > better performance on specifice low end machines and can be > > > > > leveraged by embedded platforms where applications run in controlled > > environment. > > > > > > > > I wonder if it's better to do it per driver: > > > > > > > > 1) we have device that use its own IOMMU, one example is the mlx5 > > > > vDPA device > > > > 2) we have software devices which doesn't require IOMMU at all (but > > > > still with > > > > protection) > > > > > > If I understand correctly, you’re suggesting that we create a module > > > parameter specific to the vdpa driver. Then, we can add a flag to the ‘struct > > vdpa_device’ > > > and set that flag within the vdpa driver based on the module parameter. > > > Finally, we would use this flag to taint the kernel and go in no-iommu > > > path in the vhost-vdpa driver? > > > > If it's possible, I would like to avoid changing the vDPA core. > > > > Thanks > According to my understanding of the discussion at the > https://lore.kernel.org/all/20240422164108-mutt-send-email-mst@xxxxxxxxxx, > Michael has suggested focusing on implementing a no-IOMMU mode in vdpa. > Michael, could you please confirm if it's fine to transfer all these relevant > modifications to Marvell's vdpa driver? > > Thanks. All I said is that octeon driver can be merged without this support. Then work on no-iommu can start separately. Whether this belongs in the driver or the core would depend on what the use-case is. I have not figured it out yet. What you describe seems generic not card-specific though. Jason why do you want this in the driver? > > > > > > > > > > Thanks > > > > > > > > > > > > > > Signed-off-by: Srujana Challa <schalla@xxxxxxxxxxx> > > > > > --- > > > > > drivers/vhost/vdpa.c | 23 +++++++++++++++++++++++ > > > > > 1 file changed, 23 insertions(+) > > > > > > > > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index > > > > > bc4a51e4638b..d071c30125aa 100644 > > > > > --- a/drivers/vhost/vdpa.c > > > > > +++ b/drivers/vhost/vdpa.c > > > > > @@ -36,6 +36,11 @@ enum { > > > > > > > > > > #define VHOST_VDPA_IOTLB_BUCKETS 16 > > > > > > > > > > +bool vhost_vdpa_noiommu; > > > > > +module_param_named(enable_vhost_vdpa_unsafe_noiommu_mode, > > > > > + vhost_vdpa_noiommu, bool, 0644); > > > > > +MODULE_PARM_DESC(enable_vhost_vdpa_unsafe_noiommu_mode, > > > > "Enable > > > > > +UNSAFE, no-IOMMU mode. This mode provides no device isolation, > > > > > +no DMA translation, no host kernel protection, cannot be used for > > > > > +device assignment to virtual machines, requires RAWIO > > > > > +permissions, and will taint the kernel. If you do not know what this is > > for, step away. > > > > > +(default: false)"); > > > > > + > > > > > struct vhost_vdpa_as { > > > > > struct hlist_node hash_link; > > > > > struct vhost_iotlb iotlb; > > > > > @@ -60,6 +65,7 @@ struct vhost_vdpa { > > > > > struct vdpa_iova_range range; > > > > > u32 batch_asid; > > > > > bool suspended; > > > > > + bool noiommu_en; > > > > > }; > > > > > > > > > > static DEFINE_IDA(vhost_vdpa_ida); @@ -887,6 +893,10 @@ static > > > > > void vhost_vdpa_general_unmap(struct vhost_vdpa *v, { > > > > > struct vdpa_device *vdpa = v->vdpa; > > > > > const struct vdpa_config_ops *ops = vdpa->config; > > > > > + > > > > > + if (v->noiommu_en) > > > > > + return; > > > > > + > > > > > if (ops->dma_map) { > > > > > ops->dma_unmap(vdpa, asid, map->start, map->size); > > > > > } else if (ops->set_map == NULL) { @@ -980,6 +990,9 @@ > > > > > static int vhost_vdpa_map(struct vhost_vdpa *v, struct vhost_iotlb > > *iotlb, > > > > > if (r) > > > > > return r; > > > > > > > > > > + if (v->noiommu_en) > > > > > + goto skip_map; > > > > > + > > > > > if (ops->dma_map) { > > > > > r = ops->dma_map(vdpa, asid, iova, size, pa, perm, opaque); > > > > > } else if (ops->set_map) { @@ -995,6 +1008,7 @@ static int > > > > > vhost_vdpa_map(struct vhost_vdpa *v, > > > > struct vhost_iotlb *iotlb, > > > > > return r; > > > > > } > > > > > > > > > > +skip_map: > > > > > if (!vdpa->use_va) > > > > > atomic64_add(PFN_DOWN(size), &dev->mm->pinned_vm); > > > > > > > > > > @@ -1298,6 +1312,7 @@ static int vhost_vdpa_alloc_domain(struct > > > > vhost_vdpa *v) > > > > > struct vdpa_device *vdpa = v->vdpa; > > > > > const struct vdpa_config_ops *ops = vdpa->config; > > > > > struct device *dma_dev = vdpa_get_dma_dev(vdpa); > > > > > + struct iommu_domain *domain; > > > > > const struct bus_type *bus; > > > > > int ret; > > > > > > > > > > @@ -1305,6 +1320,14 @@ static int vhost_vdpa_alloc_domain(struct > > > > vhost_vdpa *v) > > > > > if (ops->set_map || ops->dma_map) > > > > > return 0; > > > > > > > > > > + domain = iommu_get_domain_for_dev(dma_dev); > > > > > + if ((!domain || domain->type == IOMMU_DOMAIN_IDENTITY) && > > > > > + vhost_vdpa_noiommu && capable(CAP_SYS_RAWIO)) { > > > > > + add_taint(TAINT_USER, LOCKDEP_STILL_OK); > > > > > + dev_warn(&v->dev, "Adding kernel taint for noiommu > > > > > + on > > > > device\n"); > > > > > + v->noiommu_en = true; > > > > > + return 0; > > > > > + } > > > > > bus = dma_dev->bus; > > > > > if (!bus) > > > > > return -EFAULT; > > > > > -- > > > > > 2.25.1 > > > > > > > > >
