linux-kernel - [PATCH] drm/vmwgfx: Fix guests running with TDX/SEV

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Message-ID: <20250618192926.1092450-1-zack.rusin@broadcom.com>
Date: Wed, 18 Jun 2025 15:29:26 -0400
From: Zack Rusin <zack.rusin@...adcom.com>
To: dri-devel@...ts.freedesktop.org
Cc: Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	ian.forbes@...adcom.com,
	martin.krastev@...adcom.com,
	maaz.mombasawala@...adcom.com,
	Marko Kiiskila <marko.kiiskila@...adcom.com>,
	Zack Rusin <zack.rusin@...adcom.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] drm/vmwgfx: Fix guests running with TDX/SEV

From: Marko Kiiskila <marko.kiiskila@...adcom.com>

Commit 81256a50aa0f ("x86/mm: Make memremap(MEMREMAP_WB) map memory as
encrypted by default") changed the default behavior of
memremap(MEMREMAP_WB) and started mapping memory as encrypted.
The driver requires the fifo memory to be decrypted to communicate with
the host but was relaying on the old default behavior of
memremap(MEMREMAP_WB) and thus broke.

Fix it by explicitly specifying the desired behavior and passing
MEMREMAP_DEC to memremap.

Fixes: 81256a50aa0f ("x86/mm: Make memremap(MEMREMAP_WB) map memory as encrypted by default")
Signed-off-by: Marko Kiiskila <marko.kiiskila@...adcom.com>
Signed-off-by: Zack Rusin <zack.rusin@...adcom.com>
Cc: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: linux-mm@...ck.org
Cc: linux-kernel@...r.kernel.org
---
 drivers/gpu/drm/vmwgfx/vmwgfx_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
index bc0342c58b4b..8ff958d119be 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.c
@@ -750,7 +750,7 @@ static int vmw_setup_pci_resources(struct vmw_private *dev,
 		dev->fifo_mem = devm_memremap(dev->drm.dev,
 					      fifo_start,
 					      fifo_size,
-					      MEMREMAP_WB);
+					      MEMREMAP_WB | MEMREMAP_DEC);
 
 		if (IS_ERR(dev->fifo_mem)) {
 			drm_err(&dev->drm,
-- 
2.48.1