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From:   Arnd Bergmann <arnd@kernel.org>
To:     Jani Nikula <jani.nikula@linux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        Zhenyu Wang <zhenyuw@linux.intel.com>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Alex Williamson <alex.williamson@redhat.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Cornelia Huck <cohuck@redhat.com>
Cc:     Arnd Bergmann <arnd@arndb.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH] vfio/gvt: fix DRM_I915_GVT dependency on VFIO_MDEV
Date:   Thu, 22 Apr 2021 15:35:33 +0200
Message-Id: <20210422133547.1861063-1-arnd@kernel.org>
MIME-Version: 1.0
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Precedence: bulk

From: Arnd Bergmann <arnd@arndb.de>

The Kconfig dependency is incomplete since DRM_I915_GVT is a 'bool'
symbol that depends on the 'tristate' VFIO_MDEV. This allows a
configuration with VFIO_MDEV=m, DRM_I915_GVT=y and DRM_I915=y that
causes a link failure:

x86_64-linux-ld: drivers/gpu/drm/i915/gvt/gvt.o: in function `available_instances_show':
gvt.c:(.text+0x67a): undefined reference to `mtype_get_parent_dev'
x86_64-linux-ld: gvt.c:(.text+0x6a5): undefined reference to `mtype_get_type_group_id'
x86_64-linux-ld: drivers/gpu/drm/i915/gvt/gvt.o: in function `description_show':
gvt.c:(.text+0x76e): undefined reference to `mtype_get_parent_dev'
x86_64-linux-ld: gvt.c:(.text+0x799): undefined reference to `mtype_get_type_group_id'

Clarify the dependency by specifically disallowing the broken
configuration. If VFIO_MDEV is built-in, it will work, but if
VFIO_MDEV=m, the i915 driver cannot be built-in here.

Fixes: 07e543f4f9d1 ("vfio/gvt: Make DRM_I915_GVT depend on VFIO_MDEV")
Fixes: 9169cff168ff ("vfio/mdev: Correct the function signatures for the mdev_type_attributes")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/gpu/drm/i915/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/Kconfig b/drivers/gpu/drm/i915/Kconfig
index 7a5b7a93d33e..791cc9556863 100644
--- a/drivers/gpu/drm/i915/Kconfig
+++ b/drivers/gpu/drm/i915/Kconfig
@@ -111,7 +111,7 @@ config DRM_I915_GVT
 	bool "Enable Intel GVT-g graphics virtualization host support"
 	depends on DRM_I915
 	depends on 64BIT
-	depends on VFIO_MDEV
+	depends on VFIO_MDEV=y || VFIO_MDEV=DRM_I915
 	default n
 	help
 	  Choose this option if you want to enable Intel GVT-g graphics
-- 
2.29.2