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* [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup
       [not found] <2025120119-edgy-recycled-bcfe@gregkh>
@ 2025-12-01 22:10 ` Sasha Levin
  2025-12-02  7:40   ` Thomas Zimmermann
  2025-12-02 20:23 ` Sasha Levin
  1 sibling, 1 reply; 5+ messages in thread
From: Sasha Levin @ 2025-12-01 22:10 UTC (permalink / raw)
  To: stable
  Cc: Thomas Zimmermann, Javier Martinez Canillas, Alex Deucher,
	dri-devel, nouveau, amd-gfx, linux-fbdev, Sasha Levin

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
[ adapted dev->dev variable access ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/drm_fb_helper.c  | 6 ------
 drivers/video/fbdev/core/fbcon.c | 9 +++++++++
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index b15ddbd65e7b5..a8971c4eb9f05 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>
@@ -1637,10 +1635,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 
 	strcpy(fb_helper->fb->comm, "[fbcon]");
 
-	/* 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);
-
 	return 0;
 }
 
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 1fc1e47ae2b49..e681066736dea 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -65,6 +65,7 @@
 #include <linux/string.h>
 #include <linux/kd.h>
 #include <linux/panic.h>
+#include <linux/pci.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
 #include <linux/fb.h>
@@ -77,6 +78,7 @@
 #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"
@@ -2894,6 +2896,9 @@ 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--;
 
@@ -3027,6 +3032,10 @@ 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;
 }
 
-- 
2.51.0


^ permalink raw reply related	[flat|nested] 5+ messages in thread

* Re: [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup
  2025-12-01 22:10 ` [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup Sasha Levin
@ 2025-12-02  7:40   ` Thomas Zimmermann
  2025-12-02 15:52     ` Greg KH
  0 siblings, 1 reply; 5+ messages in thread
From: Thomas Zimmermann @ 2025-12-02  7:40 UTC (permalink / raw)
  To: Sasha Levin, stable
  Cc: Javier Martinez Canillas, Alex Deucher, dri-devel, nouveau,
	amd-gfx, linux-fbdev

Hi,

thanks for backporting.

You also have to remove the calls to vga_switcheroo_client_fb_set() from 
these files

https://elixir.bootlin.com/linux/v6.12/source/drivers/gpu/drm/i915/display/intel_fbdev.c
https://elixir.bootlin.com/linux/v6.12/source/drivers/gpu/drm/radeon/radeon_fbdev.c

Best regards
Thomas

Am 01.12.25 um 23:10 schrieb Sasha Levin:
> 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
> [ adapted dev->dev variable access ]
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>   drivers/gpu/drm/drm_fb_helper.c  | 6 ------
>   drivers/video/fbdev/core/fbcon.c | 9 +++++++++
>   2 files changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index b15ddbd65e7b5..a8971c4eb9f05 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>
> @@ -1637,10 +1635,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
>   
>   	strcpy(fb_helper->fb->comm, "[fbcon]");
>   
> -	/* 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);
> -
>   	return 0;
>   }
>   
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index 1fc1e47ae2b49..e681066736dea 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -65,6 +65,7 @@
>   #include <linux/string.h>
>   #include <linux/kd.h>
>   #include <linux/panic.h>
> +#include <linux/pci.h>
>   #include <linux/printk.h>
>   #include <linux/slab.h>
>   #include <linux/fb.h>
> @@ -77,6 +78,7 @@
>   #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"
> @@ -2894,6 +2896,9 @@ 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--;
>   
> @@ -3027,6 +3032,10 @@ 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;
>   }
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)



^ permalink raw reply	[flat|nested] 5+ messages in thread

* Re: [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup
  2025-12-02  7:40   ` Thomas Zimmermann
@ 2025-12-02 15:52     ` Greg KH
  0 siblings, 0 replies; 5+ messages in thread
From: Greg KH @ 2025-12-02 15:52 UTC (permalink / raw)
  To: Thomas Zimmermann
  Cc: Sasha Levin, stable, Javier Martinez Canillas, Alex Deucher,
	dri-devel, nouveau, amd-gfx, linux-fbdev

On Tue, Dec 02, 2025 at 08:40:43AM +0100, Thomas Zimmermann wrote:
> Hi,
> 
> thanks for backporting.
> 
> You also have to remove the calls to vga_switcheroo_client_fb_set() from
> these files
> 
> https://elixir.bootlin.com/linux/v6.12/source/drivers/gpu/drm/i915/display/intel_fbdev.c
> https://elixir.bootlin.com/linux/v6.12/source/drivers/gpu/drm/radeon/radeon_fbdev.c

Can you send a fixed up patch instead?

thanks,

greg k-h

^ permalink raw reply	[flat|nested] 5+ messages in thread

* [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup
       [not found] <2025120119-edgy-recycled-bcfe@gregkh>
  2025-12-01 22:10 ` [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup Sasha Levin
@ 2025-12-02 20:23 ` Sasha Levin
  2025-12-03 16:50   ` Thomas Zimmermann
  1 sibling, 1 reply; 5+ messages in thread
From: Sasha Levin @ 2025-12-02 20:23 UTC (permalink / raw)
  To: stable
  Cc: Thomas Zimmermann, Javier Martinez Canillas, Alex Deucher,
	dri-devel, nouveau, amd-gfx, linux-fbdev, Sasha Levin

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
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/gpu/drm/drm_fb_helper.c            | 6 ------
 drivers/gpu/drm/i915/display/intel_fbdev.c | 6 ------
 drivers/gpu/drm/radeon/radeon_fbdev.c      | 5 -----
 drivers/video/fbdev/core/fbcon.c           | 9 +++++++++
 4 files changed, 9 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index b15ddbd65e7b5..a8971c4eb9f05 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>
@@ -1637,10 +1635,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
 
 	strcpy(fb_helper->fb->comm, "[fbcon]");
 
-	/* 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);
-
 	return 0;
 }
 
diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
index 49a1ac4f54919..337cc9fc31b19 100644
--- a/drivers/gpu/drm/i915/display/intel_fbdev.c
+++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
@@ -589,11 +589,8 @@ static int intel_fbdev_restore_mode(struct drm_i915_private *dev_priv)
 static void intel_fbdev_client_unregister(struct drm_client_dev *client)
 {
 	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
-	struct drm_device *dev = fb_helper->dev;
-	struct pci_dev *pdev = to_pci_dev(dev->dev);
 
 	if (fb_helper->info) {
-		vga_switcheroo_client_fb_set(pdev, NULL);
 		drm_fb_helper_unregister_info(fb_helper);
 	} else {
 		drm_fb_helper_unprepare(fb_helper);
@@ -620,7 +617,6 @@ static int intel_fbdev_client_hotplug(struct drm_client_dev *client)
 {
 	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
 	struct drm_device *dev = client->dev;
-	struct pci_dev *pdev = to_pci_dev(dev->dev);
 	int ret;
 
 	if (dev->fb_helper)
@@ -634,8 +630,6 @@ static int intel_fbdev_client_hotplug(struct drm_client_dev *client)
 	if (ret)
 		goto err_drm_fb_helper_fini;
 
-	vga_switcheroo_client_fb_set(pdev, fb_helper->info);
-
 	return 0;
 
 err_drm_fb_helper_fini:
diff --git a/drivers/gpu/drm/radeon/radeon_fbdev.c b/drivers/gpu/drm/radeon/radeon_fbdev.c
index fb70de29545c6..a197ba2f2717b 100644
--- a/drivers/gpu/drm/radeon/radeon_fbdev.c
+++ b/drivers/gpu/drm/radeon/radeon_fbdev.c
@@ -300,10 +300,8 @@ static void radeon_fbdev_client_unregister(struct drm_client_dev *client)
 {
 	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
 	struct drm_device *dev = fb_helper->dev;
-	struct radeon_device *rdev = dev->dev_private;
 
 	if (fb_helper->info) {
-		vga_switcheroo_client_fb_set(rdev->pdev, NULL);
 		drm_helper_force_disable_all(dev);
 		drm_fb_helper_unregister_info(fb_helper);
 	} else {
@@ -325,7 +323,6 @@ static int radeon_fbdev_client_hotplug(struct drm_client_dev *client)
 {
 	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
 	struct drm_device *dev = client->dev;
-	struct radeon_device *rdev = dev->dev_private;
 	int ret;
 
 	if (dev->fb_helper)
@@ -342,8 +339,6 @@ static int radeon_fbdev_client_hotplug(struct drm_client_dev *client)
 	if (ret)
 		goto err_drm_fb_helper_fini;
 
-	vga_switcheroo_client_fb_set(rdev->pdev, fb_helper->info);
-
 	return 0;
 
 err_drm_fb_helper_fini:
diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 1fc1e47ae2b49..e681066736dea 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -65,6 +65,7 @@
 #include <linux/string.h>
 #include <linux/kd.h>
 #include <linux/panic.h>
+#include <linux/pci.h>
 #include <linux/printk.h>
 #include <linux/slab.h>
 #include <linux/fb.h>
@@ -77,6 +78,7 @@
 #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"
@@ -2894,6 +2896,9 @@ 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--;
 
@@ -3027,6 +3032,10 @@ 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;
 }
 
-- 
2.51.0


^ permalink raw reply related	[flat|nested] 5+ messages in thread

* Re: [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup
  2025-12-02 20:23 ` Sasha Levin
@ 2025-12-03 16:50   ` Thomas Zimmermann
  0 siblings, 0 replies; 5+ messages in thread
From: Thomas Zimmermann @ 2025-12-03 16:50 UTC (permalink / raw)
  To: Sasha Levin, stable
  Cc: Javier Martinez Canillas, Alex Deucher, dri-devel, nouveau,
	amd-gfx, linux-fbdev

Hi,

thank you for providing an updated patch.

Am 02.12.25 um 21:23 schrieb Sasha Levin:
> 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
> Signed-off-by: Sasha Levin <sashal@kernel.org>

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

> ---
>   drivers/gpu/drm/drm_fb_helper.c            | 6 ------
>   drivers/gpu/drm/i915/display/intel_fbdev.c | 6 ------
>   drivers/gpu/drm/radeon/radeon_fbdev.c      | 5 -----
>   drivers/video/fbdev/core/fbcon.c           | 9 +++++++++
>   4 files changed, 9 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index b15ddbd65e7b5..a8971c4eb9f05 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>
> @@ -1637,10 +1635,6 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper)
>   
>   	strcpy(fb_helper->fb->comm, "[fbcon]");
>   
> -	/* 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);
> -
>   	return 0;
>   }
>   
> diff --git a/drivers/gpu/drm/i915/display/intel_fbdev.c b/drivers/gpu/drm/i915/display/intel_fbdev.c
> index 49a1ac4f54919..337cc9fc31b19 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbdev.c
> @@ -589,11 +589,8 @@ static int intel_fbdev_restore_mode(struct drm_i915_private *dev_priv)
>   static void intel_fbdev_client_unregister(struct drm_client_dev *client)
>   {
>   	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
> -	struct drm_device *dev = fb_helper->dev;
> -	struct pci_dev *pdev = to_pci_dev(dev->dev);
>   
>   	if (fb_helper->info) {
> -		vga_switcheroo_client_fb_set(pdev, NULL);
>   		drm_fb_helper_unregister_info(fb_helper);
>   	} else {
>   		drm_fb_helper_unprepare(fb_helper);
> @@ -620,7 +617,6 @@ static int intel_fbdev_client_hotplug(struct drm_client_dev *client)
>   {
>   	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
>   	struct drm_device *dev = client->dev;
> -	struct pci_dev *pdev = to_pci_dev(dev->dev);
>   	int ret;
>   
>   	if (dev->fb_helper)
> @@ -634,8 +630,6 @@ static int intel_fbdev_client_hotplug(struct drm_client_dev *client)
>   	if (ret)
>   		goto err_drm_fb_helper_fini;
>   
> -	vga_switcheroo_client_fb_set(pdev, fb_helper->info);
> -
>   	return 0;
>   
>   err_drm_fb_helper_fini:
> diff --git a/drivers/gpu/drm/radeon/radeon_fbdev.c b/drivers/gpu/drm/radeon/radeon_fbdev.c
> index fb70de29545c6..a197ba2f2717b 100644
> --- a/drivers/gpu/drm/radeon/radeon_fbdev.c
> +++ b/drivers/gpu/drm/radeon/radeon_fbdev.c
> @@ -300,10 +300,8 @@ static void radeon_fbdev_client_unregister(struct drm_client_dev *client)
>   {
>   	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
>   	struct drm_device *dev = fb_helper->dev;
> -	struct radeon_device *rdev = dev->dev_private;
>   
>   	if (fb_helper->info) {
> -		vga_switcheroo_client_fb_set(rdev->pdev, NULL);
>   		drm_helper_force_disable_all(dev);
>   		drm_fb_helper_unregister_info(fb_helper);
>   	} else {
> @@ -325,7 +323,6 @@ static int radeon_fbdev_client_hotplug(struct drm_client_dev *client)
>   {
>   	struct drm_fb_helper *fb_helper = drm_fb_helper_from_client(client);
>   	struct drm_device *dev = client->dev;
> -	struct radeon_device *rdev = dev->dev_private;
>   	int ret;
>   
>   	if (dev->fb_helper)
> @@ -342,8 +339,6 @@ static int radeon_fbdev_client_hotplug(struct drm_client_dev *client)
>   	if (ret)
>   		goto err_drm_fb_helper_fini;
>   
> -	vga_switcheroo_client_fb_set(rdev->pdev, fb_helper->info);
> -
>   	return 0;
>   
>   err_drm_fb_helper_fini:
> diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> index 1fc1e47ae2b49..e681066736dea 100644
> --- a/drivers/video/fbdev/core/fbcon.c
> +++ b/drivers/video/fbdev/core/fbcon.c
> @@ -65,6 +65,7 @@
>   #include <linux/string.h>
>   #include <linux/kd.h>
>   #include <linux/panic.h>
> +#include <linux/pci.h>
>   #include <linux/printk.h>
>   #include <linux/slab.h>
>   #include <linux/fb.h>
> @@ -77,6 +78,7 @@
>   #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"
> @@ -2894,6 +2896,9 @@ 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--;
>   
> @@ -3027,6 +3032,10 @@ 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;
>   }
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)



^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2025-12-03 16:50 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
     [not found] <2025120119-edgy-recycled-bcfe@gregkh>
2025-12-01 22:10 ` [PATCH 6.12.y] drm, fbcon, vga_switcheroo: Avoid race condition in fbcon setup Sasha Levin
2025-12-02  7:40   ` Thomas Zimmermann
2025-12-02 15:52     ` Greg KH
2025-12-02 20:23 ` Sasha Levin
2025-12-03 16:50   ` Thomas Zimmermann

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