[PATCH drm-misc-next v6 5/6] drm/nouveau: make use of the GPUVM's shared dma-resv

From: Danilo Krummrich
Date: Sun Oct 08 2023 - 19:33:47 EST


DRM GEM objects private to a single GPUVM can use a shared dma-resv.
Make use of the shared dma-resv of GPUVM rather than a driver specific
one.

The shared dma-resv originates from a "root" GEM object serving as
container for the dma-resv to make it compatible with drm_exec.

In order to make sure the object proving the shared dma-resv can't be
freed up before the objects making use of it, let every such GEM object
take a reference on it.

Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
drivers/gpu/drm/nouveau/nouveau_bo.c | 11 +++++++++--
drivers/gpu/drm/nouveau/nouveau_bo.h | 5 +++++
drivers/gpu/drm/nouveau/nouveau_gem.c | 10 ++++++++--
drivers/gpu/drm/nouveau/nouveau_uvmm.c | 7 ++-----
drivers/gpu/drm/nouveau/nouveau_uvmm.h | 1 -
5 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 19cab37ac69c..dbb3facfd23d 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -148,10 +148,17 @@ nouveau_bo_del_ttm(struct ttm_buffer_object *bo)
* If nouveau_bo_new() allocated this buffer, the GEM object was never
* initialized, so don't attempt to release it.
*/
- if (bo->base.dev)
+ if (bo->base.dev) {
+ /* Gem objects not being shared with other VMs get their
+ * dma_resv from a root GEM object.
+ */
+ if (nvbo->no_share)
+ drm_gem_object_put(nvbo->r_obj);
+
drm_gem_object_release(&bo->base);
- else
+ } else {
dma_resv_fini(&bo->base._resv);
+ }

kfree(nvbo);
}
diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.h b/drivers/gpu/drm/nouveau/nouveau_bo.h
index 07f671cf895e..70c551921a9e 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.h
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.h
@@ -26,6 +26,11 @@ struct nouveau_bo {
struct list_head entry;
int pbbo_index;
bool validate_mapped;
+
+ /* Root GEM object we derive the dma_resv of in case this BO is not
+ * shared between VMs.
+ */
+ struct drm_gem_object *r_obj;
bool no_share;

/* GPU address space is independent of CPU word size */
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index c0b10d8d3d03..7715baf85c7e 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -111,7 +111,8 @@ nouveau_gem_object_open(struct drm_gem_object *gem, struct drm_file *file_priv)
if (vmm->vmm.object.oclass < NVIF_CLASS_VMM_NV50)
return 0;

- if (nvbo->no_share && uvmm && &uvmm->resv != nvbo->bo.base.resv)
+ if (nvbo->no_share && uvmm &&
+ drm_gpuvm_resv(&uvmm->base) != nvbo->bo.base.resv)
return -EPERM;

ret = ttm_bo_reserve(&nvbo->bo, false, false, NULL);
@@ -245,7 +246,7 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int align, uint32_t domain,
if (unlikely(!uvmm))
return -EINVAL;

- resv = &uvmm->resv;
+ resv = drm_gpuvm_resv(&uvmm->base);
}

if (!(domain & (NOUVEAU_GEM_DOMAIN_VRAM | NOUVEAU_GEM_DOMAIN_GART)))
@@ -288,6 +289,11 @@ nouveau_gem_new(struct nouveau_cli *cli, u64 size, int align, uint32_t domain,
if (drm->client.device.info.family >= NV_DEVICE_INFO_V0_TESLA)
nvbo->valid_domains &= domain;

+ if (nvbo->no_share) {
+ nvbo->r_obj = drm_gpuvm_resv_obj(&uvmm->base);
+ drm_gem_object_get(nvbo->r_obj);
+ }
+
*pnvbo = nvbo;
return 0;
}
diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
index 4e46f850e65f..436b0ac74ffe 100644
--- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
@@ -1841,7 +1841,6 @@ nouveau_uvmm_init(struct nouveau_uvmm *uvmm, struct nouveau_cli *cli,
int ret;

mutex_init(&uvmm->mutex);
- dma_resv_init(&uvmm->resv);
mt_init_flags(&uvmm->region_mt, MT_FLAGS_LOCK_EXTERN);
mt_set_external_lock(&uvmm->region_mt, &uvmm->mutex);

@@ -1884,14 +1883,14 @@ nouveau_uvmm_init(struct nouveau_uvmm *uvmm, struct nouveau_cli *cli,
kernel_managed_addr, kernel_managed_size,
NULL, 0, &cli->uvmm.vmm.vmm);
if (ret)
- goto out_free_gpuva_mgr;
+ goto out_gpuvm_fini;

cli->uvmm.vmm.cli = cli;
mutex_unlock(&cli->mutex);

return 0;

-out_free_gpuva_mgr:
+out_gpuvm_fini:
drm_gpuvm_destroy(&uvmm->base);
out_unlock:
mutex_unlock(&cli->mutex);
@@ -1949,6 +1948,4 @@ nouveau_uvmm_fini(struct nouveau_uvmm *uvmm)
nouveau_vmm_fini(&uvmm->vmm);
drm_gpuvm_destroy(&uvmm->base);
mutex_unlock(&cli->mutex);
-
- dma_resv_fini(&uvmm->resv);
}
diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.h b/drivers/gpu/drm/nouveau/nouveau_uvmm.h
index a308c59760a5..878cc7958483 100644
--- a/drivers/gpu/drm/nouveau/nouveau_uvmm.h
+++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.h
@@ -12,7 +12,6 @@ struct nouveau_uvmm {
struct nouveau_vmm vmm;
struct maple_tree region_mt;
struct mutex mutex;
- struct dma_resv resv;

u64 kernel_managed_addr;
u64 kernel_managed_size;
--
2.41.0