From: jsg <jsg@openbsd.org>
Date: Thu, 4 Apr 2024 07:33:22 +0000 (+0000)
Subject: drm/ttm: Make sure the mapped tt pages are decrypted when needed
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=5f11f933c5ae87a097d91f5392d8ec51e9b66d3e;p=openbsd

drm/ttm: Make sure the mapped tt pages are decrypted when needed

From Zack Rusin
de125efb3bae7720d10364a9ab6785466e4e2461 in linux-6.6.y/6.6.24
71ce046327cfd3aef3f93d1c44e091395eb03f8f in mainline linux
---

diff --git a/sys/dev/pci/drm/include/drm/ttm/ttm_tt.h b/sys/dev/pci/drm/include/drm/ttm/ttm_tt.h
index ce22c3f28b3..c44421a3fce 100644
--- a/sys/dev/pci/drm/include/drm/ttm/ttm_tt.h
+++ b/sys/dev/pci/drm/include/drm/ttm/ttm_tt.h
@@ -81,6 +81,12 @@ struct ttm_tt {
 	 *   page_flags = TTM_TT_FLAG_EXTERNAL |
 	 *		  TTM_TT_FLAG_EXTERNAL_MAPPABLE;
 	 *
+	 * TTM_TT_FLAG_DECRYPTED: The mapped ttm pages should be marked as
+	 * not encrypted. The framework will try to match what the dma layer
+	 * is doing, but note that it is a little fragile because ttm page
+	 * fault handling abuses the DMA api a bit and dma_map_attrs can't be
+	 * used to assure pgprot always matches.
+	 *
 	 * TTM_TT_FLAG_PRIV_POPULATED: TTM internal only. DO NOT USE. This is
 	 * set by TTM after ttm_tt_populate() has successfully returned, and is
 	 * then unset when TTM calls ttm_tt_unpopulate().
@@ -89,8 +95,9 @@ struct ttm_tt {
 #define TTM_TT_FLAG_ZERO_ALLOC		BIT(1)
 #define TTM_TT_FLAG_EXTERNAL		BIT(2)
 #define TTM_TT_FLAG_EXTERNAL_MAPPABLE	BIT(3)
+#define TTM_TT_FLAG_DECRYPTED		BIT(4)
 
-#define TTM_TT_FLAG_PRIV_POPULATED	BIT(4)
+#define TTM_TT_FLAG_PRIV_POPULATED	BIT(5)
 	uint32_t page_flags;
 	/** @num_pages: Number of pages in the page array. */
 	uint32_t num_pages;
diff --git a/sys/dev/pci/drm/ttm/ttm_bo_util.c b/sys/dev/pci/drm/ttm/ttm_bo_util.c
index d202b1ddf3b..a6cb1a86266 100644
--- a/sys/dev/pci/drm/ttm/ttm_bo_util.c
+++ b/sys/dev/pci/drm/ttm/ttm_bo_util.c
@@ -296,7 +296,13 @@ pgprot_t ttm_io_prot(struct ttm_buffer_object *bo, struct ttm_resource *res,
 	enum ttm_caching caching;
 
 	man = ttm_manager_type(bo->bdev, res->mem_type);
-	caching = man->use_tt ? bo->ttm->caching : res->bus.caching;
+	if (man->use_tt) {
+		caching = bo->ttm->caching;
+		if (bo->ttm->page_flags & TTM_TT_FLAG_DECRYPTED)
+			tmp = pgprot_decrypted(tmp);
+	} else  {
+		caching = res->bus.caching;
+	}
 
 	return ttm_prot_from_caching(caching, tmp);
 }
@@ -348,6 +354,8 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 		.no_wait_gpu = false
 	};
 	struct ttm_tt *ttm = bo->ttm;
+	struct ttm_resource_manager *man =
+			ttm_manager_type(bo->bdev, bo->resource->mem_type);
 	pgprot_t prot;
 	int ret;
 
@@ -357,7 +365,8 @@ static int ttm_bo_kmap_ttm(struct ttm_buffer_object *bo,
 	if (ret)
 		return ret;
 
-	if (num_pages == 1 && ttm->caching == ttm_cached) {
+	if (num_pages == 1 && ttm->caching == ttm_cached &&
+	    !(man->use_tt && (ttm->page_flags & TTM_TT_FLAG_DECRYPTED))) {
 		/*
 		 * We're mapping a single page, and the desired
 		 * page protection is consistent with the bo.
diff --git a/sys/dev/pci/drm/ttm/ttm_tt.c b/sys/dev/pci/drm/ttm/ttm_tt.c
index 21d1d9cfe70..0eee929b31d 100644
--- a/sys/dev/pci/drm/ttm/ttm_tt.c
+++ b/sys/dev/pci/drm/ttm/ttm_tt.c
@@ -31,11 +31,14 @@
 
 #define pr_fmt(fmt) "[TTM] " fmt
 
+#include <linux/cc_platform.h>
 #include <linux/sched.h>
 #include <linux/shmem_fs.h>
 #include <linux/file.h>
 #include <linux/module.h>
 #include <drm/drm_cache.h>
+#include <drm/drm_device.h>
+#include <drm/drm_util.h>
 #include <drm/ttm/ttm_bo.h>
 #include <drm/ttm/ttm_tt.h>
 
@@ -60,6 +63,7 @@ static atomic_long_t ttm_dma32_pages_allocated;
 int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc)
 {
 	struct ttm_device *bdev = bo->bdev;
+	struct drm_device *ddev = bo->base.dev;
 	uint32_t page_flags = 0;
 
 	dma_resv_assert_held(bo->base.resv);
@@ -81,6 +85,15 @@ int ttm_tt_create(struct ttm_buffer_object *bo, bool zero_alloc)
 		pr_err("Illegal buffer object type\n");
 		return -EINVAL;
 	}
+	/*
+	 * When using dma_alloc_coherent with memory encryption the
+	 * mapped TT pages need to be decrypted or otherwise the drivers
+	 * will end up sending encrypted mem to the gpu.
+	 */
+	if (bdev->pool.use_dma_alloc && cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
+		page_flags |= TTM_TT_FLAG_DECRYPTED;
+		drm_info(ddev, "TT memory decryption enabled.");
+	}
 
 	bo->ttm = bdev->funcs->ttm_tt_create(bo, page_flags);
 	if (unlikely(bo->ttm == NULL))