From aef93b36e3df3d7bfab81c21f0270e1c6e694085 Mon Sep 17 00:00:00 2001
From: riastradh <riastradh@NetBSD.org>
Date: Fri, 19 Jan 2024 22:24:38 +0000
Subject: [PATCH] i915_gem_stolen: Fill sg_pgs, with size/PAGE_SIZE entries.

Use sg_alloc_table_from_bus_dmamem to do this.

i915_gem_mman.c vm_fault_cpu and i915_gem_object_release_mmap_offset
both rely on sg_pgs to be a page array, so providing a table with
only one entry doesn't work (except by accident, if the object is
page-sized anyway).  And they rely on the sg_pgs entries to be
initialized, which we weren't doing before, and which
sg_alloc_table_from_bus_dmamem does for us.

Related to PR kern/57833.

XXX pullup-10
---
 .../drm2/dist/drm/i915/gem/i915_gem_stolen.c  | 33 +++++++++++++------
 1 file changed, 23 insertions(+), 10 deletions(-)

diff --git a/sys/external/bsd/drm2/dist/drm/i915/gem/i915_gem_stolen.c b/sys/external/bsd/drm2/dist/drm/i915/gem/i915_gem_stolen.c
index bb96d4e22848..4f06e3360989 100644
--- a/sys/external/bsd/drm2/dist/drm/i915/gem/i915_gem_stolen.c
+++ b/sys/external/bsd/drm2/dist/drm/i915/gem/i915_gem_stolen.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: i915_gem_stolen.c,v 1.6 2024/01/19 22:24:27 riastradh Exp $	*/
+/*	$NetBSD: i915_gem_stolen.c,v 1.7 2024/01/19 22:24:38 riastradh Exp $	*/
 
 /*
  * SPDX-License-Identifier: MIT
@@ -7,7 +7,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: i915_gem_stolen.c,v 1.6 2024/01/19 22:24:27 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: i915_gem_stolen.c,v 1.7 2024/01/19 22:24:38 riastradh Exp $");
 
 #include <linux/errno.h>
 #include <linux/mutex.h>
@@ -506,14 +506,13 @@ i915_pages_create_for_stolen(struct drm_device *dev,
 {
 	struct drm_i915_private *i915 = to_i915(dev);
 	struct sg_table *st;
+	struct scatterlist *sg;
 #ifdef __NetBSD__
 	bus_dma_tag_t dmat = i915->drm.dmat;
 	bus_dma_segment_t *seg = NULL;
 	int nseg = 0, i;
 	bool loaded = false;
 	int ret;
-#else
-	struct scatterlist *sg;
 #endif
 
 	GEM_BUG_ON(range_overflows(offset, size, resource_size(&i915->dsm)));
@@ -527,11 +526,6 @@ i915_pages_create_for_stolen(struct drm_device *dev,
 	if (st == NULL)
 		return ERR_PTR(-ENOMEM);
 
-	if (sg_alloc_table(st, 1, GFP_KERNEL)) {
-		kfree(st);
-		return ERR_PTR(-ENOMEM);
-	}
-
 #ifdef __NetBSD__
 	KASSERT((size % PAGE_SIZE) == 0);
 	nseg = size / PAGE_SIZE;
@@ -548,6 +542,17 @@ i915_pages_create_for_stolen(struct drm_device *dev,
 		seg[i].ds_len = PAGE_SIZE;
 	}
 
+	sg = NULL;
+
+	ret = sg_alloc_table_from_bus_dmamem(st, dmat, seg, nseg, GFP_KERNEL);
+	if (ret) {
+		DRM_ERROR("failed to alloc sg table for stolen object: %d\n",
+		    ret);
+		ret = -ENOMEM;
+		goto out;
+	}
+	sg = st->sgl;
+
 	/* XXX errno NetBSD->Linux */
 	ret = -bus_dmamap_create(dmat, size, nseg, PAGE_SIZE, 0,
 	    BUS_DMA_WAITOK, &st->sgl->sg_dmamap);
@@ -573,11 +578,19 @@ out:	kmem_free(seg, nseg * sizeof(seg[0]));
 	if (ret) {
 		if (loaded)
 			bus_dmamap_unload(dmat, st->sgl->sg_dmamap);
-		sg_free_table(st);
+		if (sg && sg->sg_dmamap)
+			bus_dmamap_destroy(dmat, sg->sg_dmamap);
+		if (sg)
+			sg_free_table(st);
 		kfree(st);
 		return ERR_PTR(ret);
 	}
 #else
+	if (sg_alloc_table(st, 1, GFP_KERNEL)) {
+		kfree(st);
+		return ERR_PTR(-ENOMEM);
+	}
+
 	sg = st->sgl;
 	sg->offset = 0;
 	sg->length = size;