FAILED: patch "[PATCH] drm/i915/migrate: Account for the reserved_space" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-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]>.

Possible dependencies:

31a2e6cbe8a4 ("drm/i915/migrate: Account for the reserved_space") 00e27ad85bc9 ("drm/i915/migrate: add acceleration support for DG2") 31d70749bfe1 ("drm/i915/migrate: fix length calculation") 08c7c122ad90 ("drm/i915/migrate: fix offset calculation") 8eb7fcce34d1 ("drm/i915/migrate: don't check the scratch page")

thanks,

greg k-h

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

From 31a2e6cbe8a4eb0d1650fff4b77872b744e14a62 Mon Sep 17 00:00:00 2001
From: Chris Wilson <[email protected]>
Date: Fri, 2 Dec 2022 12:28:42 +0000
Subject: [PATCH] drm/i915/migrate: Account for the reserved_space

If the ring is nearly full when calling into emit_pte(), we might incorrectly trample the reserved_space when constructing the packet to emit the PTEs. This then triggers the GEM_BUG_ON(rq->reserved_space > ring->space) when later submitting the request, since the request itself doesn't have enough space left in the ring to emit things like workarounds, breadcrumbs etc.

v2: Fix the whitespace errors

Testcase: igt@i915_selftests@live_emit_pte_full_ring

index b405a04135ca..b783f6f740c8 100644
@@ -342,6 +342,16 @@ static int emit_no_arbitration(struct i915_request *rq)
 	return 0;
 }
 
+static int max_pte_pkt_size(struct i915_request *rq, int pkt)
+{
+	struct intel_ring *ring = rq->ring;
+
+	pkt = min_t(int, pkt, (ring->space - rq->reserved_space) / sizeof(u32) + 5);
+	pkt = min_t(int, pkt, (ring->size - ring->emit) / sizeof(u32) + 5);
+
+	return pkt;
+}
+
 static int emit_pte(struct i915_request *rq,
 		    struct sgt_dma *it,
 		    enum i915_cache_level cache_level,

@@ -388,8 +398,7 @@ static int emit_pte(struct i915_request *rq,
 		return PTR_ERR(cs);
 
 	/* Pack as many PTE updates as possible into a single MI command */
-	pkt = min_t(int, dword_length, ring->space / sizeof(u32) + 5);
-	pkt = min_t(int, pkt, (ring->size - ring->emit) / sizeof(u32) + 5);
+	pkt = max_pte_pkt_size(rq, dword_length);
 
 	hdr = cs;
 	*cs++ = MI_STORE_DATA_IMM | REG_BIT(21); /* as qword elements */

@@ -422,8 +431,7 @@ static int emit_pte(struct i915_request *rq,
 				}
 			}
 
-			pkt = min_t(int, dword_rem, ring->space / sizeof(u32) + 5);
-			pkt = min_t(int, pkt, (ring->size - ring->emit) / sizeof(u32) + 5);
+			pkt = max_pte_pkt_size(rq, dword_rem);
 
 			hdr = cs;
 			*cs++ = MI_STORE_DATA_IMM | REG_BIT(21);