drm/etnaviv: implement softpinetnaviv/experimental

With softpin we allow the userspace to take control over the GPU virtual
address space. The new capability is relected by a bump of the minor DRM
version. There are a few restrictions for userspace to take into
account:

1. The kernel reserves a bit of the address space to implement zero page
faulting and mapping of the kernel internal ring buffer. Userspace can
query the kernel for the first usable GPU VM address via
ETNAVIV_PARAM_SOFTPIN_START_ADDR.

2. We only allow softpin on GPUs, which implement proper process
separation via PPAS. If softpin is not available the softpin start
address will be set to ~0.

3. Softpin is all or nothing. A submit using softpin must not use any
address fixups via relocs.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
---
v2: Extend 'presumed' field description to match its softpin use.

1 files changed, 25 insertions, 1 deletions

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
index 63a1206492d2..75afce42921b 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_gem_submit.c
@@ -72,6 +72,14 @@ static int submit_lookup_objects(struct etnaviv_gem_submit *submit,
 		}
 
 		submit->bos[i].flags = bo->flags;
+		if (submit->flags & ETNA_SUBMIT_SOFTPIN) {
+			if (bo->presumed < ETNAVIV_SOFTPIN_START_ADDRESS) {
+				DRM_ERROR("invalid softpin address\n");
+				ret = -EINVAL;
+				goto out_unlock;
+			}
+			submit->bos[i].va = bo->presumed;
+		}
 
 		/* normally use drm_gem_object_lookup(), but for bulk lookup
 		 * all under single table_lock just hit object_idr directly:
@@ -224,11 +232,17 @@ static int submit_pin_objects(struct etnaviv_gem_submit *submit)
 		struct etnaviv_vram_mapping *mapping;
 
 		mapping = etnaviv_gem_mapping_get(&etnaviv_obj->base,
-						  submit->mmu_context);
+						  submit->mmu_context,
+						  submit->bos[i].va);
 		if (IS_ERR(mapping)) {
 			ret = PTR_ERR(mapping);
 			break;
 		}
+
+		if ((submit->flags & ETNA_SUBMIT_SOFTPIN) &&
+		     submit->bos[i].va != mapping->iova)
+			return -EINVAL;
+
 		atomic_inc(&etnaviv_obj->gpu_active);
 
 		submit->bos[i].flags |= BO_PINNED;
@@ -261,6 +275,10 @@ static int submit_reloc(struct etnaviv_gem_submit *submit, void *stream,
 	u32 *ptr = stream;
 	int ret;
 
+	/* Submits using softpin don't blend with relocs */
+	if ((submit->flags & ETNA_SUBMIT_SOFTPIN) && nr_relocs != 0)
+		return -EINVAL;
+
 	for (i = 0; i < nr_relocs; i++) {
 		const struct drm_etnaviv_gem_submit_reloc *r = relocs + i;
 		struct etnaviv_gem_submit_bo *bo;
@@ -445,6 +463,12 @@ int etnaviv_ioctl_gem_submit(struct drm_device *dev, void *data,
 		return -EINVAL;
 	}
 
+	if ((args->flags & ETNA_SUBMIT_SOFTPIN) &&
+	    priv->mmu_global->version != ETNAVIV_IOMMU_V2) {
+		DRM_ERROR("softpin requested on incompatible MMU\n");
+		return -EINVAL;
+	}
+
 	/*
 	 * Copy the command submission and bo array to kernel space in
 	 * one go, and do this outside of any locks.