linux-kernel - [PATCH 1/2] drm/gpuvm: Send in-place re-maps to the driver as remap

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Message-ID: <20250723221213.36325-2-robin.clark@oss.qualcomm.com>
Date: Wed, 23 Jul 2025 15:12:11 -0700
From: Rob Clark <robin.clark@....qualcomm.com>
To: dri-devel@...ts.freedesktop.org
Cc: linux-arm-msm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        Danilo Krummrich <dakr@...hat.com>,
        Connor Abbott <cwabbott0@...il.com>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Lyude Paul <lyude@...hat.com>, Danilo Krummrich <dakr@...nel.org>,
        linux-kernel@...r.kernel.org (open list),
        nouveau@...ts.freedesktop.org (open list:DRM DRIVER FOR NVIDIA GEFORCE/QUADRO GPUS)
Subject: [PATCH 1/2] drm/gpuvm: Send in-place re-maps to the driver as remap

The 'keep' hint on the unmap is only half useful, without being able to
link it to a map cb.  Instead combine the two ops into a remap op to
give the driver a chance to figure things out.

Signed-off-by: Rob Clark <robin.clark@....qualcomm.com>
---
In theory, drivers should treat an unmap+map combined in a remap step
the same as discreet unmap+map steps.

AFAICT nouveau is only driver using the keep hint, and this was missing
for the remap callback.  So I've added that.

But this is only tested on msm.

 drivers/gpu/drm/drm_gpuvm.c            | 21 +++++++++++++++++++++
 drivers/gpu/drm/nouveau/nouveau_uvmm.c |  3 ++-
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
index bbc7fecb6f4a..e21782a97fbe 100644
--- a/drivers/gpu/drm/drm_gpuvm.c
+++ b/drivers/gpu/drm/drm_gpuvm.c
@@ -2125,6 +2125,27 @@ __drm_gpuvm_sm_map(struct drm_gpuvm *gpuvm,
 				 offset == req_offset;
 
 			if (end == req_end) {
+				if (merge) {
+					/*
+					 * This is an exact remap of the existing
+					 * VA (potentially flags change)?  Pass
+					 * this to the driver as a remap so it can
+					 * do an in-place update:
+					 */
+					struct drm_gpuva_op_map n = {
+						.va.addr = va->va.addr,
+						.va.range = va->va.range,
+						.gem.obj = va->gem.obj,
+						.gem.offset = va->gem.offset,
+					};
+					struct drm_gpuva_op_unmap u = {
+						.va = va,
+						.keep = true,
+					};
+
+					return op_remap_cb(ops, priv, NULL, &n, &u);
+				}
+
 				ret = op_unmap_cb(ops, priv, va, merge);
 				if (ret)
 					return ret;
diff --git a/drivers/gpu/drm/nouveau/nouveau_uvmm.c b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
index 48f105239f42..c3e3a15eb3c8 100644
--- a/drivers/gpu/drm/nouveau/nouveau_uvmm.c
+++ b/drivers/gpu/drm/nouveau/nouveau_uvmm.c
@@ -820,7 +820,8 @@ op_remap(struct drm_gpuva_op_remap *r,
 	if (r->next)
 		end = r->next->va.addr;
 
-	op_unmap_range(u, addr, end - addr);
+	if (!u->keep)
+		op_unmap_range(u, addr, end - addr);
 }
 
 static int
-- 
2.50.1