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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Boris Brezillon <boris.brezillon@collabora.com>,
        Steven Price <steven.price@arm.com>
Subject: [PATCH 5.4 040/244] drm/panfrost: Dont try to map pages that are already mapped
Date:   Wed, 12 May 2021 16:46:51 +0200
Message-Id: <20210512144744.334442699@linuxfoundation.org>
In-Reply-To: <20210512144743.039977287@linuxfoundation.org>
References: <20210512144743.039977287@linuxfoundation.org>
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From: Boris Brezillon <boris.brezillon@collabora.com>

commit f45da8204ff1707c529a8769f5467ff16f504b26 upstream.

We allocate 2MB chunks at a time, so it might appear that a page fault
has already been handled by a previous page fault when we reach
panfrost_mmu_map_fault_addr(). Bail out in that case to avoid mapping the
same area twice.

Cc: <stable@vger.kernel.org>
Fixes: 187d2929206e ("drm/panfrost: Add support for GPU heap allocations")
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210205111757.585248-3-boris.brezillon@collabora.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/panfrost/panfrost_mmu.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
+++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
@@ -494,8 +494,14 @@ static int panfrost_mmu_map_fault_addr(s
 		}
 		bo->base.pages = pages;
 		bo->base.pages_use_count = 1;
-	} else
+	} else {
 		pages = bo->base.pages;
+		if (pages[page_offset]) {
+			/* Pages are already mapped, bail out. */
+			mutex_unlock(&bo->base.pages_lock);
+			goto out;
+		}
+	}
 
 	mapping = bo->base.base.filp->f_mapping;
 	mapping_set_unevictable(mapping);
@@ -529,6 +535,7 @@ static int panfrost_mmu_map_fault_addr(s
 
 	dev_dbg(pfdev->dev, "mapped page fault @ AS%d %llx", as, addr);
 
+out:
 	panfrost_gem_mapping_put(bomapping);
 
 	return 0;