Nouveau - Jun 2023 - [PATCH v7 6/8] PCI/VGA: Introduce is_boot_device function callback to vga_client_register

From: Sui Jingfeng <suijingfeng at loongson.cn>

The vga_is_firmware_default() function is arch-dependent, it's probably
wrong if we simply remove the arch guard. As the VRAM BAR which contains
firmware framebuffer may move, while the lfb_base and lfb_size members of
the screen_info does not change accordingly. In short, it should take the
re-allocation of the PCI BAR into consideration.

With the observation that device drivers or video aperture helpers may
have better knowledge about which PCI bar contains the firmware fb,
which could avoid the need to iterate all of the PCI BARs. But as a PCI
function at pci/vgaarb.c, vga_is_firmware_default() is not suitable to
make such an optimization since it is loaded too early.

There are PCI display controllers that don't have a dedicated VRAM bar,
this function will lose its effectiveness in such a case. Luckily, the
device driver can provide an accurate workaround.

Therefore, this patch introduces a callback that allows the device driver
to tell the VGAARB if the device is the default boot device. This patch
only intends to introduce the mechanism, while the implementation is left
to the device driver authors. Also honor the comment: "Clients have two
callback mechanisms they can use"

Cc: Alex Deucher <alexander.deucher at amd.com>
Cc: Christian Konig <christian.koenig at amd.com>
Cc: Pan Xinhui <Xinhui.Pan at amd.com>
Cc: David Airlie <airlied at gmail.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Jani Nikula <jani.nikula at linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: Karol Herbst <kherbst at redhat.com>
Cc: Lyude Paul <lyude at redhat.com>
Cc: Bjorn Helgaas <bhelgaas at google.com>
Cc: Alex Williamson <alex.williamson at redhat.com>
Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Maxime Ripard <mripard at kernel.org>
Cc: Thomas Zimmermann <tzimmermann at suse.de>
Cc: Hawking Zhang <Hawking.Zhang at amd.com>
Cc: Mario Limonciello <mario.limonciello at amd.com>
Cc: Lijo Lazar <lijo.lazar at amd.com>
Cc: YiPeng Chai <YiPeng.Chai at amd.com>
Cc: Bokun Zhang <Bokun.Zhang at amd.com>
Cc: Likun Gao <Likun.Gao at amd.com>
Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
Cc: Jason Gunthorpe <jgg at ziepe.ca>
CC: Kevin Tian <kevin.tian at intel.com>
Cc: Cornelia Huck <cohuck at redhat.com>
Cc: Yishai Hadas <yishaih at nvidia.com>
Cc: Abhishek Sahu <abhsahu at nvidia.com>
Cc: Yi Liu <yi.l.liu at intel.com>
Signed-off-by: Sui Jingfeng <suijingfeng at loongson.cn>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  2 +-
 drivers/gpu/drm/i915/display/intel_vga.c   |  3 +--
 drivers/gpu/drm/nouveau/nouveau_vga.c      |  2 +-
 drivers/gpu/drm/radeon/radeon_device.c     |  2 +-
 drivers/pci/vgaarb.c                       | 21 ++++++++++++++++++++-
 drivers/vfio/pci/vfio_pci_core.c           |  2 +-
 include/linux/vgaarb.h                     |  8 +++++---
 7 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 5c7d40873ee2..7a096f2d5c16 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3960,7 +3960,7 @@ int amdgpu_device_init(struct amdgpu_device *adev,
 	/* this will fail for cards that aren't VGA class devices, just
 	 * ignore it */
 	if ((adev->pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
-		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode);
+		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode, NULL);
 
 	px = amdgpu_device_supports_px(ddev);
 
diff --git a/drivers/gpu/drm/i915/display/intel_vga.c
b/drivers/gpu/drm/i915/display/intel_vga.c
index 286a0bdd28c6..98d7d4dffe9f 100644
--- a/drivers/gpu/drm/i915/display/intel_vga.c
+++ b/drivers/gpu/drm/i915/display/intel_vga.c
@@ -115,7 +115,6 @@ intel_vga_set_decode(struct pci_dev *pdev, bool
enable_decode)
 
 int intel_vga_register(struct drm_i915_private *i915)
 {
-
 	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
 	int ret;
 
@@ -127,7 +126,7 @@ int intel_vga_register(struct drm_i915_private *i915)
 	 * then we do not take part in VGA arbitration and the
 	 * vga_client_register() fails with -ENODEV.
 	 */
-	ret = vga_client_register(pdev, intel_vga_set_decode);
+	ret = vga_client_register(pdev, intel_vga_set_decode, NULL);
 	if (ret && ret != -ENODEV)
 		return ret;
 
diff --git a/drivers/gpu/drm/nouveau/nouveau_vga.c
b/drivers/gpu/drm/nouveau/nouveau_vga.c
index f8bf0ec26844..162b4f4676c7 100644
--- a/drivers/gpu/drm/nouveau/nouveau_vga.c
+++ b/drivers/gpu/drm/nouveau/nouveau_vga.c
@@ -92,7 +92,7 @@ nouveau_vga_init(struct nouveau_drm *drm)
 		return;
 	pdev = to_pci_dev(dev->dev);
 
-	vga_client_register(pdev, nouveau_vga_set_decode);
+	vga_client_register(pdev, nouveau_vga_set_decode, NULL);
 
 	/* don't register Thunderbolt eGPU with vga_switcheroo */
 	if (pci_is_thunderbolt_attached(pdev))
diff --git a/drivers/gpu/drm/radeon/radeon_device.c
b/drivers/gpu/drm/radeon/radeon_device.c
index afbb3a80c0c6..71f2ff39d6a1 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -1425,7 +1425,7 @@ int radeon_device_init(struct radeon_device *rdev,
 	/* if we have > 1 VGA cards, then disable the radeon VGA resources */
 	/* this will fail for cards that aren't VGA class devices, just
 	 * ignore it */
-	vga_client_register(rdev->pdev, radeon_vga_set_decode);
+	vga_client_register(rdev->pdev, radeon_vga_set_decode, NULL);
 
 	if (rdev->flags & RADEON_IS_PX)
 		runtime = true;
diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
index ceb914245383..c574898380f0 100644
--- a/drivers/pci/vgaarb.c
+++ b/drivers/pci/vgaarb.c
@@ -53,6 +53,7 @@ struct vga_device {
 	bool bridge_has_one_vga;
 	bool is_firmware_default;	/* device selected by firmware */
 	unsigned int (*set_decode)(struct pci_dev *pdev, bool decode);
+	bool (*is_boot_device)(struct pci_dev *pdev);
 };
 
 static LIST_HEAD(vga_list);
@@ -969,6 +970,10 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
  * @set_decode callback: If a client can disable its GPU VGA resource, it
  * will get a callback from this to set the encode/decode state.
  *
+ * @is_boot_device: callback to the device driver, query if a client is the
+ * default boot device, as the device driver typically has better knowledge
+ * if specific device is the boot device. But this callback is optional.
+ *
  * Rationale: we cannot disable VGA decode resources unconditionally, some
  * single GPU laptops seem to require ACPI or BIOS access to the VGA registers
  * to control things like backlights etc. Hopefully newer multi-GPU laptops do
@@ -984,7 +989,8 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
  * Returns: 0 on success, -1 on failure
  */
 int vga_client_register(struct pci_dev *pdev,
-		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode))
+		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode),
+		bool (*is_boot_device)(struct pci_dev *pdev))
 {
 	int ret = -ENODEV;
 	struct vga_device *vgadev;
@@ -996,6 +1002,7 @@ int vga_client_register(struct pci_dev *pdev,
 		goto bail;
 
 	vgadev->set_decode = set_decode;
+	vgadev->is_boot_device = is_boot_device;
 	ret = 0;
 
 bail:
@@ -1523,6 +1530,18 @@ static int pci_notify(struct notifier_block *nb, unsigned
long action,
 		notify = vga_arbiter_add_pci_device(pdev);
 	else if (action == BUS_NOTIFY_DEL_DEVICE)
 		notify = vga_arbiter_del_pci_device(pdev);
+	else if (action == BUS_NOTIFY_BOUND_DRIVER) {
+		struct vga_device *vgadev = vgadev_find(pdev);
+		bool boot_dev = false;
+
+		if (vgadev && vgadev->is_boot_device)
+			boot_dev = vgadev->is_boot_device(pdev);
+
+		if (boot_dev) {
+			vgaarb_info(&pdev->dev, "Set as boot device (dictated by
driver)\n");
+			vga_set_default_device(pdev);
+		}
+	}
 
 	vgaarb_dbg(dev, "%s: action = %lu\n", __func__, action);
 
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index a5ab416cf476..2a8873a330ba 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -2067,7 +2067,7 @@ static int vfio_pci_vga_init(struct vfio_pci_core_device
*vdev)
 	if (ret)
 		return ret;
 
-	ret = vga_client_register(pdev, vfio_pci_set_decode);
+	ret = vga_client_register(pdev, vfio_pci_set_decode, NULL);
 	if (ret)
 		return ret;
 	vga_set_legacy_decoding(pdev, vfio_pci_set_decode(pdev, false));
diff --git a/include/linux/vgaarb.h b/include/linux/vgaarb.h
index 97129a1bbb7d..dfde5a6ba55a 100644
--- a/include/linux/vgaarb.h
+++ b/include/linux/vgaarb.h
@@ -33,7 +33,8 @@ struct pci_dev *vga_default_device(void);
 void vga_set_default_device(struct pci_dev *pdev);
 int vga_remove_vgacon(struct pci_dev *pdev);
 int vga_client_register(struct pci_dev *pdev,
-		unsigned int (*set_decode)(struct pci_dev *pdev, bool state));
+		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
+		bool (*is_boot_device)(struct pci_dev *pdev));
 #else /* CONFIG_VGA_ARB */
 static inline void vga_set_legacy_decoding(struct pci_dev *pdev,
 		unsigned int decodes)
@@ -59,7 +60,8 @@ static inline int vga_remove_vgacon(struct pci_dev *pdev)
 	return 0;
 }
 static inline int vga_client_register(struct pci_dev *pdev,
-		unsigned int (*set_decode)(struct pci_dev *pdev, bool state))
+		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
+		bool (*is_boot_device)(struct pci_dev *pdev))
 {
 	return 0;
 }
@@ -97,7 +99,7 @@ static inline int vga_get_uninterruptible(struct pci_dev
*pdev,
 
 static inline void vga_client_unregister(struct pci_dev *pdev)
 {
-	vga_client_register(pdev, NULL);
+	vga_client_register(pdev, NULL, NULL);
 }
 
 #endif /* LINUX_VGA_H */
-- 
2.25.1

Hi,


A nouveau developer(Lyude) from redhat send me a R-B,

Thanks for the developers of nouveau project.


Please allow me add a link[1] here.


[1] 
https://lore.kernel.org/all/0afadc69f99a36bc9d03ecf54ff25859dbc10e28.camel at
redhat.com/


On 2023/6/13 11:01, Sui Jingfeng wrote:
> From: Sui Jingfeng <suijingfeng at loongson.cn>
>
> The vga_is_firmware_default() function is arch-dependent, it's probably
> wrong if we simply remove the arch guard. As the VRAM BAR which contains
> firmware framebuffer may move, while the lfb_base and lfb_size members of
> the screen_info does not change accordingly. In short, it should take the
> re-allocation of the PCI BAR into consideration.
>
> With the observation that device drivers or video aperture helpers may
> have better knowledge about which PCI bar contains the firmware fb,
> which could avoid the need to iterate all of the PCI BARs. But as a PCI
> function at pci/vgaarb.c, vga_is_firmware_default() is not suitable to
> make such an optimization since it is loaded too early.
>
> There are PCI display controllers that don't have a dedicated VRAM bar,
> this function will lose its effectiveness in such a case. Luckily, the
> device driver can provide an accurate workaround.
>
> Therefore, this patch introduces a callback that allows the device driver
> to tell the VGAARB if the device is the default boot device. This patch
> only intends to introduce the mechanism, while the implementation is left
> to the device driver authors. Also honor the comment: "Clients have
two
> callback mechanisms they can use"
>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Christian Konig <christian.koenig at amd.com>
> Cc: Pan Xinhui <Xinhui.Pan at amd.com>
> Cc: David Airlie <airlied at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: Karol Herbst <kherbst at redhat.com>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Bjorn Helgaas <bhelgaas at google.com>
> Cc: Alex Williamson <alex.williamson at redhat.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Hawking Zhang <Hawking.Zhang at amd.com>
> Cc: Mario Limonciello <mario.limonciello at amd.com>
> Cc: Lijo Lazar <lijo.lazar at amd.com>
> Cc: YiPeng Chai <YiPeng.Chai at amd.com>
> Cc: Bokun Zhang <Bokun.Zhang at amd.com>
> Cc: Likun Gao <Likun.Gao at amd.com>
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Jason Gunthorpe <jgg at ziepe.ca>
> CC: Kevin Tian <kevin.tian at intel.com>
> Cc: Cornelia Huck <cohuck at redhat.com>
> Cc: Yishai Hadas <yishaih at nvidia.com>
> Cc: Abhishek Sahu <abhsahu at nvidia.com>
> Cc: Yi Liu <yi.l.liu at intel.com>
> Signed-off-by: Sui Jingfeng <suijingfeng at loongson.cn>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  2 +-
>   drivers/gpu/drm/i915/display/intel_vga.c   |  3 +--
>   drivers/gpu/drm/nouveau/nouveau_vga.c      |  2 +-
>   drivers/gpu/drm/radeon/radeon_device.c     |  2 +-
>   drivers/pci/vgaarb.c                       | 21 ++++++++++++++++++++-
>   drivers/vfio/pci/vfio_pci_core.c           |  2 +-
>   include/linux/vgaarb.h                     |  8 +++++---
>   7 files changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 5c7d40873ee2..7a096f2d5c16 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -3960,7 +3960,7 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>   	/* this will fail for cards that aren't VGA class devices, just
>   	 * ignore it */
>   	if ((adev->pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
> -		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode);
> +		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode, NULL);
>   
>   	px = amdgpu_device_supports_px(ddev);
>   
> diff --git a/drivers/gpu/drm/i915/display/intel_vga.c
b/drivers/gpu/drm/i915/display/intel_vga.c
> index 286a0bdd28c6..98d7d4dffe9f 100644
> --- a/drivers/gpu/drm/i915/display/intel_vga.c
> +++ b/drivers/gpu/drm/i915/display/intel_vga.c
> @@ -115,7 +115,6 @@ intel_vga_set_decode(struct pci_dev *pdev, bool
enable_decode)
>   
>   int intel_vga_register(struct drm_i915_private *i915)
>   {
> -
>   	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
>   	int ret;
>   
> @@ -127,7 +126,7 @@ int intel_vga_register(struct drm_i915_private *i915)
>   	 * then we do not take part in VGA arbitration and the
>   	 * vga_client_register() fails with -ENODEV.
>   	 */
> -	ret = vga_client_register(pdev, intel_vga_set_decode);
> +	ret = vga_client_register(pdev, intel_vga_set_decode, NULL);
>   	if (ret && ret != -ENODEV)
>   		return ret;
>   
> diff --git a/drivers/gpu/drm/nouveau/nouveau_vga.c
b/drivers/gpu/drm/nouveau/nouveau_vga.c
> index f8bf0ec26844..162b4f4676c7 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_vga.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_vga.c
> @@ -92,7 +92,7 @@ nouveau_vga_init(struct nouveau_drm *drm)
>   		return;
>   	pdev = to_pci_dev(dev->dev);
>   
> -	vga_client_register(pdev, nouveau_vga_set_decode);
> +	vga_client_register(pdev, nouveau_vga_set_decode, NULL);
>   
>   	/* don't register Thunderbolt eGPU with vga_switcheroo */
>   	if (pci_is_thunderbolt_attached(pdev))
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c
b/drivers/gpu/drm/radeon/radeon_device.c
> index afbb3a80c0c6..71f2ff39d6a1 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1425,7 +1425,7 @@ int radeon_device_init(struct radeon_device *rdev,
>   	/* if we have > 1 VGA cards, then disable the radeon VGA resources */
>   	/* this will fail for cards that aren't VGA class devices, just
>   	 * ignore it */
> -	vga_client_register(rdev->pdev, radeon_vga_set_decode);
> +	vga_client_register(rdev->pdev, radeon_vga_set_decode, NULL);
>   
>   	if (rdev->flags & RADEON_IS_PX)
>   		runtime = true;
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index ceb914245383..c574898380f0 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -53,6 +53,7 @@ struct vga_device {
>   	bool bridge_has_one_vga;
>   	bool is_firmware_default;	/* device selected by firmware */
>   	unsigned int (*set_decode)(struct pci_dev *pdev, bool decode);
> +	bool (*is_boot_device)(struct pci_dev *pdev);
>   };
>   
>   static LIST_HEAD(vga_list);
> @@ -969,6 +970,10 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
>    * @set_decode callback: If a client can disable its GPU VGA resource, it
>    * will get a callback from this to set the encode/decode state.
>    *
> + * @is_boot_device: callback to the device driver, query if a client is
the
> + * default boot device, as the device driver typically has better
knowledge
> + * if specific device is the boot device. But this callback is optional.
> + *
>    * Rationale: we cannot disable VGA decode resources unconditionally,
some
>    * single GPU laptops seem to require ACPI or BIOS access to the VGA
registers
>    * to control things like backlights etc. Hopefully newer multi-GPU
laptops do
> @@ -984,7 +989,8 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
>    * Returns: 0 on success, -1 on failure
>    */
>   int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode))
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode),
> +		bool (*is_boot_device)(struct pci_dev *pdev))
>   {
>   	int ret = -ENODEV;
>   	struct vga_device *vgadev;
> @@ -996,6 +1002,7 @@ int vga_client_register(struct pci_dev *pdev,
>   		goto bail;
>   
>   	vgadev->set_decode = set_decode;
> +	vgadev->is_boot_device = is_boot_device;
>   	ret = 0;
>   
>   bail:
> @@ -1523,6 +1530,18 @@ static int pci_notify(struct notifier_block *nb,
unsigned long action,
>   		notify = vga_arbiter_add_pci_device(pdev);
>   	else if (action == BUS_NOTIFY_DEL_DEVICE)
>   		notify = vga_arbiter_del_pci_device(pdev);
> +	else if (action == BUS_NOTIFY_BOUND_DRIVER) {
> +		struct vga_device *vgadev = vgadev_find(pdev);
> +		bool boot_dev = false;
> +
> +		if (vgadev && vgadev->is_boot_device)
> +			boot_dev = vgadev->is_boot_device(pdev);
> +
> +		if (boot_dev) {
> +			vgaarb_info(&pdev->dev, "Set as boot device (dictated by
driver)\n");
> +			vga_set_default_device(pdev);
> +		}
> +	}
>   
>   	vgaarb_dbg(dev, "%s: action = %lu\n", __func__, action);
>   
> diff --git a/drivers/vfio/pci/vfio_pci_core.c
b/drivers/vfio/pci/vfio_pci_core.c
> index a5ab416cf476..2a8873a330ba 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -2067,7 +2067,7 @@ static int vfio_pci_vga_init(struct
vfio_pci_core_device *vdev)
>   	if (ret)
>   		return ret;
>   
> -	ret = vga_client_register(pdev, vfio_pci_set_decode);
> +	ret = vga_client_register(pdev, vfio_pci_set_decode, NULL);
>   	if (ret)
>   		return ret;
>   	vga_set_legacy_decoding(pdev, vfio_pci_set_decode(pdev, false));
> diff --git a/include/linux/vgaarb.h b/include/linux/vgaarb.h
> index 97129a1bbb7d..dfde5a6ba55a 100644
> --- a/include/linux/vgaarb.h
> +++ b/include/linux/vgaarb.h
> @@ -33,7 +33,8 @@ struct pci_dev *vga_default_device(void);
>   void vga_set_default_device(struct pci_dev *pdev);
>   int vga_remove_vgacon(struct pci_dev *pdev);
>   int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool state));
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
> +		bool (*is_boot_device)(struct pci_dev *pdev));
>   #else /* CONFIG_VGA_ARB */
>   static inline void vga_set_legacy_decoding(struct pci_dev *pdev,
>   		unsigned int decodes)
> @@ -59,7 +60,8 @@ static inline int vga_remove_vgacon(struct pci_dev *pdev)
>   	return 0;
>   }
>   static inline int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool state))
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
> +		bool (*is_boot_device)(struct pci_dev *pdev))
>   {
>   	return 0;
>   }
> @@ -97,7 +99,7 @@ static inline int vga_get_uninterruptible(struct pci_dev
*pdev,
>   
>   static inline void vga_client_unregister(struct pci_dev *pdev)
>   {
> -	vga_client_register(pdev, NULL);
> +	vga_client_register(pdev, NULL, NULL);
>   }
>   
>   #endif /* LINUX_VGA_H */
-- 
Jingfeng

PING ?

On 2023/6/13 11:01, Sui Jingfeng wrote:
> From: Sui Jingfeng <suijingfeng at loongson.cn>
>
> The vga_is_firmware_default() function is arch-dependent, it's probably
> wrong if we simply remove the arch guard. As the VRAM BAR which contains
> firmware framebuffer may move, while the lfb_base and lfb_size members of
> the screen_info does not change accordingly. In short, it should take the
> re-allocation of the PCI BAR into consideration.
>
> With the observation that device drivers or video aperture helpers may
> have better knowledge about which PCI bar contains the firmware fb,
> which could avoid the need to iterate all of the PCI BARs. But as a PCI
> function at pci/vgaarb.c, vga_is_firmware_default() is not suitable to
> make such an optimization since it is loaded too early.
>
> There are PCI display controllers that don't have a dedicated VRAM bar,
> this function will lose its effectiveness in such a case. Luckily, the
> device driver can provide an accurate workaround.
>
> Therefore, this patch introduces a callback that allows the device driver
> to tell the VGAARB if the device is the default boot device. This patch
> only intends to introduce the mechanism, while the implementation is left
> to the device driver authors. Also honor the comment: "Clients have
two
> callback mechanisms they can use"
>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Christian Konig <christian.koenig at amd.com>
> Cc: Pan Xinhui <Xinhui.Pan at amd.com>
> Cc: David Airlie <airlied at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: Karol Herbst <kherbst at redhat.com>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Bjorn Helgaas <bhelgaas at google.com>
> Cc: Alex Williamson <alex.williamson at redhat.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Hawking Zhang <Hawking.Zhang at amd.com>
> Cc: Mario Limonciello <mario.limonciello at amd.com>
> Cc: Lijo Lazar <lijo.lazar at amd.com>
> Cc: YiPeng Chai <YiPeng.Chai at amd.com>
> Cc: Bokun Zhang <Bokun.Zhang at amd.com>
> Cc: Likun Gao <Likun.Gao at amd.com>
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Jason Gunthorpe <jgg at ziepe.ca>
> CC: Kevin Tian <kevin.tian at intel.com>
> Cc: Cornelia Huck <cohuck at redhat.com>
> Cc: Yishai Hadas <yishaih at nvidia.com>
> Cc: Abhishek Sahu <abhsahu at nvidia.com>
> Cc: Yi Liu <yi.l.liu at intel.com>
> Signed-off-by: Sui Jingfeng <suijingfeng at loongson.cn>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  2 +-
>   drivers/gpu/drm/i915/display/intel_vga.c   |  3 +--
>   drivers/gpu/drm/nouveau/nouveau_vga.c      |  2 +-
>   drivers/gpu/drm/radeon/radeon_device.c     |  2 +-
>   drivers/pci/vgaarb.c                       | 21 ++++++++++++++++++++-
>   drivers/vfio/pci/vfio_pci_core.c           |  2 +-
>   include/linux/vgaarb.h                     |  8 +++++---
>   7 files changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 5c7d40873ee2..7a096f2d5c16 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -3960,7 +3960,7 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>   	/* this will fail for cards that aren't VGA class devices, just
>   	 * ignore it */
>   	if ((adev->pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
> -		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode);
> +		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode, NULL);
>   
>   	px = amdgpu_device_supports_px(ddev);
>   
> diff --git a/drivers/gpu/drm/i915/display/intel_vga.c
b/drivers/gpu/drm/i915/display/intel_vga.c
> index 286a0bdd28c6..98d7d4dffe9f 100644
> --- a/drivers/gpu/drm/i915/display/intel_vga.c
> +++ b/drivers/gpu/drm/i915/display/intel_vga.c
> @@ -115,7 +115,6 @@ intel_vga_set_decode(struct pci_dev *pdev, bool
enable_decode)
>   
>   int intel_vga_register(struct drm_i915_private *i915)
>   {
> -
>   	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
>   	int ret;
>   
> @@ -127,7 +126,7 @@ int intel_vga_register(struct drm_i915_private *i915)
>   	 * then we do not take part in VGA arbitration and the
>   	 * vga_client_register() fails with -ENODEV.
>   	 */
> -	ret = vga_client_register(pdev, intel_vga_set_decode);
> +	ret = vga_client_register(pdev, intel_vga_set_decode, NULL);
>   	if (ret && ret != -ENODEV)
>   		return ret;
>   
> diff --git a/drivers/gpu/drm/nouveau/nouveau_vga.c
b/drivers/gpu/drm/nouveau/nouveau_vga.c
> index f8bf0ec26844..162b4f4676c7 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_vga.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_vga.c
> @@ -92,7 +92,7 @@ nouveau_vga_init(struct nouveau_drm *drm)
>   		return;
>   	pdev = to_pci_dev(dev->dev);
>   
> -	vga_client_register(pdev, nouveau_vga_set_decode);
> +	vga_client_register(pdev, nouveau_vga_set_decode, NULL);
>   
>   	/* don't register Thunderbolt eGPU with vga_switcheroo */
>   	if (pci_is_thunderbolt_attached(pdev))
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c
b/drivers/gpu/drm/radeon/radeon_device.c
> index afbb3a80c0c6..71f2ff39d6a1 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1425,7 +1425,7 @@ int radeon_device_init(struct radeon_device *rdev,
>   	/* if we have > 1 VGA cards, then disable the radeon VGA resources */
>   	/* this will fail for cards that aren't VGA class devices, just
>   	 * ignore it */
> -	vga_client_register(rdev->pdev, radeon_vga_set_decode);
> +	vga_client_register(rdev->pdev, radeon_vga_set_decode, NULL);
>   
>   	if (rdev->flags & RADEON_IS_PX)
>   		runtime = true;
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index ceb914245383..c574898380f0 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -53,6 +53,7 @@ struct vga_device {
>   	bool bridge_has_one_vga;
>   	bool is_firmware_default;	/* device selected by firmware */
>   	unsigned int (*set_decode)(struct pci_dev *pdev, bool decode);
> +	bool (*is_boot_device)(struct pci_dev *pdev);
>   };
>   
>   static LIST_HEAD(vga_list);
> @@ -969,6 +970,10 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
>    * @set_decode callback: If a client can disable its GPU VGA resource, it
>    * will get a callback from this to set the encode/decode state.
>    *
> + * @is_boot_device: callback to the device driver, query if a client is
the
> + * default boot device, as the device driver typically has better
knowledge
> + * if specific device is the boot device. But this callback is optional.
> + *
>    * Rationale: we cannot disable VGA decode resources unconditionally,
some
>    * single GPU laptops seem to require ACPI or BIOS access to the VGA
registers
>    * to control things like backlights etc. Hopefully newer multi-GPU
laptops do
> @@ -984,7 +989,8 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
>    * Returns: 0 on success, -1 on failure
>    */
>   int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode))
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode),
> +		bool (*is_boot_device)(struct pci_dev *pdev))
>   {
>   	int ret = -ENODEV;
>   	struct vga_device *vgadev;
> @@ -996,6 +1002,7 @@ int vga_client_register(struct pci_dev *pdev,
>   		goto bail;
>   
>   	vgadev->set_decode = set_decode;
> +	vgadev->is_boot_device = is_boot_device;
>   	ret = 0;
>   
>   bail:
> @@ -1523,6 +1530,18 @@ static int pci_notify(struct notifier_block *nb,
unsigned long action,
>   		notify = vga_arbiter_add_pci_device(pdev);
>   	else if (action == BUS_NOTIFY_DEL_DEVICE)
>   		notify = vga_arbiter_del_pci_device(pdev);
> +	else if (action == BUS_NOTIFY_BOUND_DRIVER) {
> +		struct vga_device *vgadev = vgadev_find(pdev);
> +		bool boot_dev = false;
> +
> +		if (vgadev && vgadev->is_boot_device)
> +			boot_dev = vgadev->is_boot_device(pdev);
> +
> +		if (boot_dev) {
> +			vgaarb_info(&pdev->dev, "Set as boot device (dictated by
driver)\n");
> +			vga_set_default_device(pdev);
> +		}
> +	}
>   
>   	vgaarb_dbg(dev, "%s: action = %lu\n", __func__, action);
>   
> diff --git a/drivers/vfio/pci/vfio_pci_core.c
b/drivers/vfio/pci/vfio_pci_core.c
> index a5ab416cf476..2a8873a330ba 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -2067,7 +2067,7 @@ static int vfio_pci_vga_init(struct
vfio_pci_core_device *vdev)
>   	if (ret)
>   		return ret;
>   
> -	ret = vga_client_register(pdev, vfio_pci_set_decode);
> +	ret = vga_client_register(pdev, vfio_pci_set_decode, NULL);
>   	if (ret)
>   		return ret;
>   	vga_set_legacy_decoding(pdev, vfio_pci_set_decode(pdev, false));
> diff --git a/include/linux/vgaarb.h b/include/linux/vgaarb.h
> index 97129a1bbb7d..dfde5a6ba55a 100644
> --- a/include/linux/vgaarb.h
> +++ b/include/linux/vgaarb.h
> @@ -33,7 +33,8 @@ struct pci_dev *vga_default_device(void);
>   void vga_set_default_device(struct pci_dev *pdev);
>   int vga_remove_vgacon(struct pci_dev *pdev);
>   int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool state));
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
> +		bool (*is_boot_device)(struct pci_dev *pdev));
>   #else /* CONFIG_VGA_ARB */
>   static inline void vga_set_legacy_decoding(struct pci_dev *pdev,
>   		unsigned int decodes)
> @@ -59,7 +60,8 @@ static inline int vga_remove_vgacon(struct pci_dev *pdev)
>   	return 0;
>   }
>   static inline int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool state))
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
> +		bool (*is_boot_device)(struct pci_dev *pdev))
>   {
>   	return 0;
>   }
> @@ -97,7 +99,7 @@ static inline int vga_get_uninterruptible(struct pci_dev
*pdev,
>   
>   static inline void vga_client_unregister(struct pci_dev *pdev)
>   {
> -	vga_client_register(pdev, NULL);
> +	vga_client_register(pdev, NULL, NULL);
>   }
>   
>   #endif /* LINUX_VGA_H */
-- 
Jingfeng

Hi,


Humble ping !


Please share some bandwidth to help reviewing this series, OK ?


As this series is useful for all architecture, I have tested on my X86, 
mips and LoongArch computer.

Questions and comments is also welcome.

If no one response within three days,

I'm going to send a updated version with another trivial improvement, OK?

On 2023/6/13 11:01, Sui Jingfeng wrote:
> From: Sui Jingfeng <suijingfeng at loongson.cn>
>
> The vga_is_firmware_default() function is arch-dependent, it's probably
> wrong if we simply remove the arch guard. As the VRAM BAR which contains
> firmware framebuffer may move, while the lfb_base and lfb_size members of
> the screen_info does not change accordingly. In short, it should take the
> re-allocation of the PCI BAR into consideration.
>
> With the observation that device drivers or video aperture helpers may
> have better knowledge about which PCI bar contains the firmware fb,
> which could avoid the need to iterate all of the PCI BARs. But as a PCI
> function at pci/vgaarb.c, vga_is_firmware_default() is not suitable to
> make such an optimization since it is loaded too early.
>
> There are PCI display controllers that don't have a dedicated VRAM bar,
> this function will lose its effectiveness in such a case. Luckily, the
> device driver can provide an accurate workaround.
>
> Therefore, this patch introduces a callback that allows the device driver
> to tell the VGAARB if the device is the default boot device. This patch
> only intends to introduce the mechanism, while the implementation is left
> to the device driver authors. Also honor the comment: "Clients have
two
> callback mechanisms they can use"
>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Christian Konig <christian.koenig at amd.com>
> Cc: Pan Xinhui <Xinhui.Pan at amd.com>
> Cc: David Airlie <airlied at gmail.com>
> Cc: Daniel Vetter <daniel at ffwll.ch>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Cc: Ben Skeggs <bskeggs at redhat.com>
> Cc: Karol Herbst <kherbst at redhat.com>
> Cc: Lyude Paul <lyude at redhat.com>
> Cc: Bjorn Helgaas <bhelgaas at google.com>
> Cc: Alex Williamson <alex.williamson at redhat.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <mripard at kernel.org>
> Cc: Thomas Zimmermann <tzimmermann at suse.de>
> Cc: Hawking Zhang <Hawking.Zhang at amd.com>
> Cc: Mario Limonciello <mario.limonciello at amd.com>
> Cc: Lijo Lazar <lijo.lazar at amd.com>
> Cc: YiPeng Chai <YiPeng.Chai at amd.com>
> Cc: Bokun Zhang <Bokun.Zhang at amd.com>
> Cc: Likun Gao <Likun.Gao at amd.com>
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Jason Gunthorpe <jgg at ziepe.ca>
> CC: Kevin Tian <kevin.tian at intel.com>
> Cc: Cornelia Huck <cohuck at redhat.com>
> Cc: Yishai Hadas <yishaih at nvidia.com>
> Cc: Abhishek Sahu <abhsahu at nvidia.com>
> Cc: Yi Liu <yi.l.liu at intel.com>
> Signed-off-by: Sui Jingfeng <suijingfeng at loongson.cn>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  2 +-
>   drivers/gpu/drm/i915/display/intel_vga.c   |  3 +--
>   drivers/gpu/drm/nouveau/nouveau_vga.c      |  2 +-
>   drivers/gpu/drm/radeon/radeon_device.c     |  2 +-
>   drivers/pci/vgaarb.c                       | 21 ++++++++++++++++++++-
>   drivers/vfio/pci/vfio_pci_core.c           |  2 +-
>   include/linux/vgaarb.h                     |  8 +++++---
>   7 files changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 5c7d40873ee2..7a096f2d5c16 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -3960,7 +3960,7 @@ int amdgpu_device_init(struct amdgpu_device *adev,
>   	/* this will fail for cards that aren't VGA class devices, just
>   	 * ignore it */
>   	if ((adev->pdev->class >> 8) == PCI_CLASS_DISPLAY_VGA)
> -		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode);
> +		vga_client_register(adev->pdev, amdgpu_device_vga_set_decode, NULL);
>   
>   	px = amdgpu_device_supports_px(ddev);
>   
> diff --git a/drivers/gpu/drm/i915/display/intel_vga.c
b/drivers/gpu/drm/i915/display/intel_vga.c
> index 286a0bdd28c6..98d7d4dffe9f 100644
> --- a/drivers/gpu/drm/i915/display/intel_vga.c
> +++ b/drivers/gpu/drm/i915/display/intel_vga.c
> @@ -115,7 +115,6 @@ intel_vga_set_decode(struct pci_dev *pdev, bool
enable_decode)
>   
>   int intel_vga_register(struct drm_i915_private *i915)
>   {
> -
>   	struct pci_dev *pdev = to_pci_dev(i915->drm.dev);
>   	int ret;
>   
> @@ -127,7 +126,7 @@ int intel_vga_register(struct drm_i915_private *i915)
>   	 * then we do not take part in VGA arbitration and the
>   	 * vga_client_register() fails with -ENODEV.
>   	 */
> -	ret = vga_client_register(pdev, intel_vga_set_decode);
> +	ret = vga_client_register(pdev, intel_vga_set_decode, NULL);
>   	if (ret && ret != -ENODEV)
>   		return ret;
>   
> diff --git a/drivers/gpu/drm/nouveau/nouveau_vga.c
b/drivers/gpu/drm/nouveau/nouveau_vga.c
> index f8bf0ec26844..162b4f4676c7 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_vga.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_vga.c
> @@ -92,7 +92,7 @@ nouveau_vga_init(struct nouveau_drm *drm)
>   		return;
>   	pdev = to_pci_dev(dev->dev);
>   
> -	vga_client_register(pdev, nouveau_vga_set_decode);
> +	vga_client_register(pdev, nouveau_vga_set_decode, NULL);
>   
>   	/* don't register Thunderbolt eGPU with vga_switcheroo */
>   	if (pci_is_thunderbolt_attached(pdev))
> diff --git a/drivers/gpu/drm/radeon/radeon_device.c
b/drivers/gpu/drm/radeon/radeon_device.c
> index afbb3a80c0c6..71f2ff39d6a1 100644
> --- a/drivers/gpu/drm/radeon/radeon_device.c
> +++ b/drivers/gpu/drm/radeon/radeon_device.c
> @@ -1425,7 +1425,7 @@ int radeon_device_init(struct radeon_device *rdev,
>   	/* if we have > 1 VGA cards, then disable the radeon VGA resources */
>   	/* this will fail for cards that aren't VGA class devices, just
>   	 * ignore it */
> -	vga_client_register(rdev->pdev, radeon_vga_set_decode);
> +	vga_client_register(rdev->pdev, radeon_vga_set_decode, NULL);
>   
>   	if (rdev->flags & RADEON_IS_PX)
>   		runtime = true;
> diff --git a/drivers/pci/vgaarb.c b/drivers/pci/vgaarb.c
> index ceb914245383..c574898380f0 100644
> --- a/drivers/pci/vgaarb.c
> +++ b/drivers/pci/vgaarb.c
> @@ -53,6 +53,7 @@ struct vga_device {
>   	bool bridge_has_one_vga;
>   	bool is_firmware_default;	/* device selected by firmware */
>   	unsigned int (*set_decode)(struct pci_dev *pdev, bool decode);
> +	bool (*is_boot_device)(struct pci_dev *pdev);
>   };
>   
>   static LIST_HEAD(vga_list);
> @@ -969,6 +970,10 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
>    * @set_decode callback: If a client can disable its GPU VGA resource, it
>    * will get a callback from this to set the encode/decode state.
>    *
> + * @is_boot_device: callback to the device driver, query if a client is
the
> + * default boot device, as the device driver typically has better
knowledge
> + * if specific device is the boot device. But this callback is optional.
> + *
>    * Rationale: we cannot disable VGA decode resources unconditionally,
some
>    * single GPU laptops seem to require ACPI or BIOS access to the VGA
registers
>    * to control things like backlights etc. Hopefully newer multi-GPU
laptops do
> @@ -984,7 +989,8 @@ EXPORT_SYMBOL(vga_set_legacy_decoding);
>    * Returns: 0 on success, -1 on failure
>    */
>   int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode))
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool decode),
> +		bool (*is_boot_device)(struct pci_dev *pdev))
>   {
>   	int ret = -ENODEV;
>   	struct vga_device *vgadev;
> @@ -996,6 +1002,7 @@ int vga_client_register(struct pci_dev *pdev,
>   		goto bail;
>   
>   	vgadev->set_decode = set_decode;
> +	vgadev->is_boot_device = is_boot_device;
>   	ret = 0;
>   
>   bail:
> @@ -1523,6 +1530,18 @@ static int pci_notify(struct notifier_block *nb,
unsigned long action,
>   		notify = vga_arbiter_add_pci_device(pdev);
>   	else if (action == BUS_NOTIFY_DEL_DEVICE)
>   		notify = vga_arbiter_del_pci_device(pdev);
> +	else if (action == BUS_NOTIFY_BOUND_DRIVER) {
> +		struct vga_device *vgadev = vgadev_find(pdev);
> +		bool boot_dev = false;
> +
> +		if (vgadev && vgadev->is_boot_device)
> +			boot_dev = vgadev->is_boot_device(pdev);
> +
> +		if (boot_dev) {
> +			vgaarb_info(&pdev->dev, "Set as boot device (dictated by
driver)\n");
> +			vga_set_default_device(pdev);
> +		}
> +	}
>   
>   	vgaarb_dbg(dev, "%s: action = %lu\n", __func__, action);
>   
> diff --git a/drivers/vfio/pci/vfio_pci_core.c
b/drivers/vfio/pci/vfio_pci_core.c
> index a5ab416cf476..2a8873a330ba 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -2067,7 +2067,7 @@ static int vfio_pci_vga_init(struct
vfio_pci_core_device *vdev)
>   	if (ret)
>   		return ret;
>   
> -	ret = vga_client_register(pdev, vfio_pci_set_decode);
> +	ret = vga_client_register(pdev, vfio_pci_set_decode, NULL);
>   	if (ret)
>   		return ret;
>   	vga_set_legacy_decoding(pdev, vfio_pci_set_decode(pdev, false));
> diff --git a/include/linux/vgaarb.h b/include/linux/vgaarb.h
> index 97129a1bbb7d..dfde5a6ba55a 100644
> --- a/include/linux/vgaarb.h
> +++ b/include/linux/vgaarb.h
> @@ -33,7 +33,8 @@ struct pci_dev *vga_default_device(void);
>   void vga_set_default_device(struct pci_dev *pdev);
>   int vga_remove_vgacon(struct pci_dev *pdev);
>   int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool state));
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
> +		bool (*is_boot_device)(struct pci_dev *pdev));
>   #else /* CONFIG_VGA_ARB */
>   static inline void vga_set_legacy_decoding(struct pci_dev *pdev,
>   		unsigned int decodes)
> @@ -59,7 +60,8 @@ static inline int vga_remove_vgacon(struct pci_dev *pdev)
>   	return 0;
>   }
>   static inline int vga_client_register(struct pci_dev *pdev,
> -		unsigned int (*set_decode)(struct pci_dev *pdev, bool state))
> +		unsigned int (*set_decode)(struct pci_dev *pdev, bool state),
> +		bool (*is_boot_device)(struct pci_dev *pdev))
>   {
>   	return 0;
>   }
> @@ -97,7 +99,7 @@ static inline int vga_get_uninterruptible(struct pci_dev
*pdev,
>   
>   static inline void vga_client_unregister(struct pci_dev *pdev)
>   {
> -	vga_client_register(pdev, NULL);
> +	vga_client_register(pdev, NULL, NULL);
>   }
>   
>   #endif /* LINUX_VGA_H */