[PATCH 6.6.y 1/2] drm/fbdev-helper: Set and clear VGA switcheroo client from fb_info

[PATCH 6.6.y 1/2] drm/fbdev-helper: Set and clear VGA switcheroo client from fb_info

[Wenshan Lan]

From: Thomas Zimmermann <tzimmermann@suse.de>

[ Upstream commit 02257549daf7ff839e2be6d4f3cac975e522fd7a ]

Call vga_switcheroo_client_fb_set() with the PCI device from the
instance of struct fb_info. All fbdev clients now run these calls.
For non-PCI devices or drivers without vga-switcheroo, this does
nothing. For i915 and radeon, it allows these drivers to use a
common fbdev client.

The device is the same as the one stored in struct drm_client and
struct drm_fb_helper, so there is no difference in behavior. Some
NULL-pointer checks are being removed, where those pointers cannot
be NULL.

v4:
- clarify call semantics for drm_fb_helper_unregister_info() (Javier)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240924071734.98201-3-tzimmermann@suse.de
[ The variable 'dev' in the function drm_fb_helper_single_fb_probe() is
unused; remove it in v6.6. ]
Signed-off-by: Wenshan Lan <jetlan9@163.com>
---
 drivers/gpu/drm/drm_fb_helper.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index b507c1c008a3..eee7b56d441f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -567,7 +567,7 @@ EXPORT_SYMBOL(drm_fb_helper_release_info);
 
 /**
  * drm_fb_helper_unregister_info - unregister fb_info framebuffer device
- * @fb_helper: driver-allocated fbdev helper, can be NULL
+ * @fb_helper: driver-allocated fbdev helper, must not be NULL
  *
  * A wrapper around unregister_framebuffer, to release the fb_info
  * framebuffer device. This must be called before releasing all resources for
@@ -575,8 +575,12 @@ EXPORT_SYMBOL(drm_fb_helper_release_info);
  */
 void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper)
 {
-	if (fb_helper && fb_helper->info)
-		unregister_framebuffer(fb_helper->info);
+	struct fb_info *info = fb_helper->info;
+	struct device *dev = info->device;
+
+	if (dev_is_pci(dev))
+		vga_switcheroo_client_fb_set(to_pci_dev(dev), NULL);
+	unregister_framebuffer(fb_helper->info);
 }
 EXPORT_SYMBOL(drm_fb_helper_unregister_info);
 
@@ -1668,8 +1672,8 @@ static int drm_fb_helper_find_sizes(struct drm_fb_helper *fb_helper,
 static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 {
 	struct drm_client_dev *client = &fb_helper->client;
-	struct drm_device *dev = fb_helper->dev;
 	struct drm_fb_helper_surface_size sizes;
+	struct fb_info *info;
 	int ret;
 
 	ret = drm_fb_helper_find_sizes(fb_helper, &sizes);
@@ -1687,9 +1691,11 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 
 	strcpy(fb_helper->fb->comm, "[fbcon]");
 
+	info = fb_helper->info;
+
 	/* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */
-	if (dev_is_pci(dev->dev))
-		vga_switcheroo_client_fb_set(to_pci_dev(dev->dev), fb_helper->info);
+	if (dev_is_pci(info->device))
+		vga_switcheroo_client_fb_set(to_pci_dev(info->device), info);
 
 	return 0;
 }
-- 
2.43.0

[PATCH 6.6.y 2/2] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup

[Wenshan Lan]

From: Thomas Zimmermann <tzimmermann@suse.de>

[ Upstream commit eb76d0f5553575599561010f24c277cc5b31d003 ]

Protect vga_switcheroo_client_fb_set() with console lock. Avoids OOB
access in fbcon_remap_all(). Without holding the console lock the call
races with switching outputs.

VGA switcheroo calls fbcon_remap_all() when switching clients. The fbcon
function uses struct fb_info.node, which is set by register_framebuffer().
As the fb-helper code currently sets up VGA switcheroo before registering
the framebuffer, the value of node is -1 and therefore not a legal value.
For example, fbcon uses the value within set_con2fb_map() [1] as an index
into an array.

Moving vga_switcheroo_client_fb_set() after register_framebuffer() can
result in VGA switching that does not switch fbcon correctly.

Therefore move vga_switcheroo_client_fb_set() under fbcon_fb_registered(),
which already holds the console lock. Fbdev calls fbcon_fb_registered()
from within register_framebuffer(). Serializes the helper with VGA
switcheroo's call to fbcon_remap_all().

Although vga_switcheroo_client_fb_set() takes an instance of struct fb_info
as parameter, it really only needs the contained fbcon state. Moving the
call to fbcon initialization is therefore cleaner than before. Only amdgpu,
i915, nouveau and radeon support vga_switcheroo. For all other drivers,
this change does nothing.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://elixir.bootlin.com/linux/v6.17/source/drivers/video/fbdev/core/fbcon.c#L2942 # [1]
Fixes: 6a9ee8af344e ("vga_switcheroo: initial implementation (v15)")
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Cc: dri-devel@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: amd-gfx@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Cc: <stable@vger.kernel.org> # v2.6.34+
Link: https://patch.msgid.link/20251105161549.98836-1-tzimmermann@suse.de
[ Minor context conflict resolved. ]
Signed-off-by: Wenshan Lan <jetlan9@163.com>
---
 drivers/gpu/drm/drm_fb_helper.c  | 14 --------------
 drivers/video/fbdev/core/fbcon.c |  9 +++++++++
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index eee7b56d441f..9691c93f19a0 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -30,9 +30,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/console.h>
-#include <linux/pci.h>
 #include <linux/sysrq.h>
-#include <linux/vga_switcheroo.h>
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_drv.h>
@@ -575,11 +573,6 @@ EXPORT_SYMBOL(drm_fb_helper_release_info);
  */
 void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper)
 {
-	struct fb_info *info = fb_helper->info;
-	struct device *dev = info->device;
-
-	if (dev_is_pci(dev))
-		vga_switcheroo_client_fb_set(to_pci_dev(dev), NULL);
 	unregister_framebuffer(fb_helper->info);
 }
 EXPORT_SYMBOL(drm_fb_helper_unregister_info);
@@ -1673,7 +1666,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 {
 	struct drm_client_dev *client = &fb_helper->client;
 	struct drm_fb_helper_surface_size sizes;
-	struct fb_info *info;
 	int ret;
 
 	ret = drm_fb_helper_find_sizes(fb_helper, &sizes);
@@ -1691,12 +1683,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 
 	strcpy(fb_helper->fb->comm, "[fbcon]");
 
-	info = fb_helper->info;
-
-	/* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */
-	if (dev_is_pci(info->device))
-		vga_switcheroo_client_fb_set(to_pci_dev(info->device), info);
-
 	return 0;
 }
 
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 703c4e851612..d1ac4e45eea6 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -64,6 +64,7 @@
 #include <linux/console.h>
 #include <linux/string.h>
 #include <linux/kd.h>
+#include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/fb.h>
 #include <linux/fbcon.h>
@@ -75,6 +76,7 @@
 #include <linux/interrupt.h>
 #include <linux/crc32.h> /* For counting font checksums */
 #include <linux/uaccess.h>
+#include <linux/vga_switcheroo.h>
 #include <asm/irq.h>
 
 #include "fbcon.h"
@@ -2914,6 +2916,9 @@ void fbcon_fb_unregistered(struct fb_info *info)
 
 	console_lock();
 
+	if (info->device && dev_is_pci(info->device))
+		vga_switcheroo_client_fb_set(to_pci_dev(info->device), NULL);
+
 	fbcon_registered_fb[info->node] = NULL;
 	fbcon_num_registered_fb--;
 
@@ -3047,6 +3052,10 @@ static int do_fb_registered(struct fb_info *info)
 		}
 	}
 
+	/* Set the fb info for vga_switcheroo clients. Does nothing otherwise. */
+	if (info->device && dev_is_pci(info->device))
+		vga_switcheroo_client_fb_set(to_pci_dev(info->device), info);
+
 	return ret;
 }
 
-- 
2.43.0

[PATCH 6.6.y 2/2] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup

[Wenshan Lan]

From: Thomas Zimmermann <tzimmermann@suse.de>

[ Upstream commit eb76d0f5553575599561010f24c277cc5b31d003 ]

Protect vga_switcheroo_client_fb_set() with console lock. Avoids OOB
access in fbcon_remap_all(). Without holding the console lock the call
races with switching outputs.

VGA switcheroo calls fbcon_remap_all() when switching clients. The fbcon
function uses struct fb_info.node, which is set by register_framebuffer().
As the fb-helper code currently sets up VGA switcheroo before registering
the framebuffer, the value of node is -1 and therefore not a legal value.
For example, fbcon uses the value within set_con2fb_map() [1] as an index
into an array.

Moving vga_switcheroo_client_fb_set() after register_framebuffer() can
result in VGA switching that does not switch fbcon correctly.

Therefore move vga_switcheroo_client_fb_set() under fbcon_fb_registered(),
which already holds the console lock. Fbdev calls fbcon_fb_registered()
from within register_framebuffer(). Serializes the helper with VGA
switcheroo's call to fbcon_remap_all().

Although vga_switcheroo_client_fb_set() takes an instance of struct fb_info
as parameter, it really only needs the contained fbcon state. Moving the
call to fbcon initialization is therefore cleaner than before. Only amdgpu,
i915, nouveau and radeon support vga_switcheroo. For all other drivers,
this change does nothing.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://elixir.bootlin.com/linux/v6.17/source/drivers/video/fbdev/core/fbcon.c#L2942 # [1]
Fixes: 6a9ee8af344e ("vga_switcheroo: initial implementation (v15)")
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Cc: dri-devel@lists.freedesktop.org
Cc: nouveau@lists.freedesktop.org
Cc: amd-gfx@lists.freedesktop.org
Cc: linux-fbdev@vger.kernel.org
Cc: <stable@vger.kernel.org> # v2.6.34+
Link: https://patch.msgid.link/20251105161549.98836-1-tzimmermann@suse.de
[ Minor context conflict resolved. ]
Signed-off-by: Wenshan Lan <jetlan9@163.com>
---
 drivers/gpu/drm/drm_fb_helper.c  | 14 --------------
 drivers/video/fbdev/core/fbcon.c |  9 +++++++++
 2 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index eee7b56d441f..9691c93f19a0 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -30,9 +30,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <linux/console.h>
-#include <linux/pci.h>
 #include <linux/sysrq.h>
-#include <linux/vga_switcheroo.h>
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_drv.h>
@@ -575,11 +573,6 @@ EXPORT_SYMBOL(drm_fb_helper_release_info);
  */
 void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper)
 {
-	struct fb_info *info = fb_helper->info;
-	struct device *dev = info->device;
-
-	if (dev_is_pci(dev))
-		vga_switcheroo_client_fb_set(to_pci_dev(dev), NULL);
 	unregister_framebuffer(fb_helper->info);
 }
 EXPORT_SYMBOL(drm_fb_helper_unregister_info);
@@ -1673,7 +1666,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 {
 	struct drm_client_dev *client = &fb_helper->client;
 	struct drm_fb_helper_surface_size sizes;
-	struct fb_info *info;
 	int ret;
 
 	ret = drm_fb_helper_find_sizes(fb_helper, &sizes);
@@ -1691,12 +1683,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 
 	strcpy(fb_helper->fb->comm, "[fbcon]");
 
-	info = fb_helper->info;
-
-	/* Set the fb info for vgaswitcheroo clients. Does nothing otherwise. */
-	if (dev_is_pci(info->device))
-		vga_switcheroo_client_fb_set(to_pci_dev(info->device), info);
-
 	return 0;
 }
 
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 703c4e851612..d1ac4e45eea6 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -64,6 +64,7 @@
 #include <linux/console.h>
 #include <linux/string.h>
 #include <linux/kd.h>
+#include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/fb.h>
 #include <linux/fbcon.h>
@@ -75,6 +76,7 @@
 #include <linux/interrupt.h>
 #include <linux/crc32.h> /* For counting font checksums */
 #include <linux/uaccess.h>
+#include <linux/vga_switcheroo.h>
 #include <asm/irq.h>
 
 #include "fbcon.h"
@@ -2914,6 +2916,9 @@ void fbcon_fb_unregistered(struct fb_info *info)
 
 	console_lock();
 
+	if (info->device && dev_is_pci(info->device))
+		vga_switcheroo_client_fb_set(to_pci_dev(info->device), NULL);
+
 	fbcon_registered_fb[info->node] = NULL;
 	fbcon_num_registered_fb--;
 
@@ -3047,6 +3052,10 @@ static int do_fb_registered(struct fb_info *info)
 		}
 	}
 
+	/* Set the fb info for vga_switcheroo clients. Does nothing otherwise. */
+	if (info->device && dev_is_pci(info->device))
+		vga_switcheroo_client_fb_set(to_pci_dev(info->device), info);
+
 	return ret;
 }
 
-- 
2.43.0

Re: [PATCH 6.6.y 1/2] drm/fbdev-helper: Set and clear VGA switcheroo client from fb_info

[Sasha Levin]

Queued for 6.6.y, thanks.

-- 
Thanks,
Sasha