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FAILED: patch "[PATCH] drm/i915/gt: Fill all the unused space in the GGTT" failed to apply to 5.6-stable tree

PATCH [email protected] 2 participants 2 messages Apr 15, 2020 – Apr 16, 2020

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#0 lore raw

The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0b72a251bf92ca2378530fa1f9b35a71830ab51c Mon Sep 17 00:00:00 2001
From: Chris Wilson <[email protected]>
Date: Tue, 31 Mar 2020 16:23:48 +0100
Subject: [PATCH] drm/i915/gt: Fill all the unused space in the GGTT

When we allocate space in the GGTT we may have to allocate a larger region than will be populated by the object to accommodate fencing. Make sure that this space beyond the end of the buffer points safely into scratch space, in case the HW tries to access it anyway (e.g. fenced access to the last tile row).

v2: Preemptively / conservatively guard gen6 ggtt as well.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/1554

drivers/gpu/drm/i915/gt/intel_ggtt.c +27 -10
index aed498a0d032..4c5a209cb669 100644
@@ -191,10 +191,11 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm,
 				     enum i915_cache_level level,
 				     u32 flags)
 {
-	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
-	struct sgt_iter sgt_iter;
-	gen8_pte_t __iomem *gtt_entries;
 	const gen8_pte_t pte_encode = gen8_ggtt_pte_encode(0, level, 0);
+	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
+	gen8_pte_t __iomem *gte;
+	gen8_pte_t __iomem *end;
+	struct sgt_iter iter;
 	dma_addr_t addr;
 
 	/*
@@ -202,10 +203,17 @@ static void gen8_ggtt_insert_entries(struct i915_address_space *vm,
 	 * not to allow the user to override access to a read only page.
 	 */
 
-	gtt_entries = (gen8_pte_t __iomem *)ggtt->gsm;
-	gtt_entries += vma->node.start / I915_GTT_PAGE_SIZE;
-	for_each_sgt_daddr(addr, sgt_iter, vma->pages)
-		gen8_set_pte(gtt_entries++, pte_encode | addr);
+	gte = (gen8_pte_t __iomem *)ggtt->gsm;
+	gte += vma->node.start / I915_GTT_PAGE_SIZE;
+	end = gte + vma->node.size / I915_GTT_PAGE_SIZE;
+
+	for_each_sgt_daddr(addr, iter, vma->pages)
+		gen8_set_pte(gte++, pte_encode | addr);
+	GEM_BUG_ON(gte > end);
+
+	/* Fill the allocated but "unused" space beyond the end of the buffer */
+	while (gte < end)
+		gen8_set_pte(gte++, vm->scratch[0].encode);
 
 	/*
 	 * We want to flush the TLBs only after we're certain all the PTE
@@ -241,13 +249,22 @@ static void gen6_ggtt_insert_entries(struct i915_address_space *vm,
 				     u32 flags)
 {
 	struct i915_ggtt *ggtt = i915_vm_to_ggtt(vm);
-	gen6_pte_t __iomem *entries = (gen6_pte_t __iomem *)ggtt->gsm;
-	unsigned int i = vma->node.start / I915_GTT_PAGE_SIZE;
+	gen6_pte_t __iomem *gte;
+	gen6_pte_t __iomem *end;
 	struct sgt_iter iter;
 	dma_addr_t addr;
 
+	gte = (gen6_pte_t __iomem *)ggtt->gsm;
+	gte += vma->node.start / I915_GTT_PAGE_SIZE;
+	end = gte + vma->node.size / I915_GTT_PAGE_SIZE;
+
 	for_each_sgt_daddr(addr, iter, vma->pages)
-		iowrite32(vm->pte_encode(addr, level, flags), &entries[i++]);
+		iowrite32(vm->pte_encode(addr, level, flags), gte++);
+	GEM_BUG_ON(gte > end);
+
+	/* Fill the allocated but "unused" space beyond the end of the buffer */
+	while (gte < end)
+		iowrite32(vm->scratch[0].encode, gte++);
 
 	/*
 	 * We want to flush the TLBs only after we're certain all the PTE
maintainer
#1 lore raw
Quoted 27 lines · On Wed, Apr 15, 2020 at 01:35:39PM +0200, [email protected] wrote:

The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 0b72a251bf92ca2378530fa1f9b35a71830ab51c Mon Sep 17 00:00:00 2001
From: Chris Wilson <[email protected]>
Date: Tue, 31 Mar 2020 16:23:48 +0100
Subject: [PATCH] drm/i915/gt: Fill all the unused space in the GGTT

When we allocate space in the GGTT we may have to allocate a larger region than will be populated by the object to accommodate fencing. Make sure that this space beyond the end of the buffer points safely into scratch space, in case the HW tries to access it anyway (e.g. fenced access to the last tile row).

v2: Preemptively / conservatively guard gen6 ggtt as well.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/1554

Quoted 9 lines

I've also grabbed 69edc390a542 ("drm/i915/ggtt: do not set bits 1-11 in gen12 ptes").

Signature · 2 lines
Thanks,
Sasha