[PATCH v3 0/2] fbdev: hyperv_fb: framebuffer release cleanup

[PATCH v3 0/2] fbdev: hyperv_fb: framebuffer release cleanup

[Saurabh Sengar]

This patch series addresses an issue in the unbind path of the hyperv_fb
driver, which is resolved in the second patch of this series.

While working on this fix, it was observed that hvfb_putmem() and its
child functions could be cleaned up first to simplify the movement of
hvfb_putmem(). This cleanup is done in the first patch.

Although hvfb_getmem() could also be cleaned up, it depends on
vmbus_allocate_mmio(), which is used by multiple other drivers. Since
addressing hvfb_getmem() is independent of this fix, it will be handled
in a separate patch series.

[V3]
 - Add a patch 1 for cleanup of hvfb_putmem()
 - Use the simplified hvfb_putmem()

Saurabh Sengar (2):
  fbdev: hyperv_fb: Simplify hvfb_putmem
  fbdev: hyperv_fb: Allow graceful removal of framebuffer

 drivers/video/fbdev/hyperv_fb.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

-- 
2.43.0

[PATCH v3 1/2] fbdev: hyperv_fb: Simplify hvfb_putmem

[Saurabh Sengar]

The device object required in 'hvfb_release_phymem' function
for 'dma_free_coherent' can also be obtained from the 'info'
pointer, making 'hdev' parameter in 'hvfb_putmem' redundant.
Remove the unnecessary 'hdev' argument from 'hvfb_putmem'.

Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
---
 drivers/video/fbdev/hyperv_fb.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
index 363e4ccfcdb7..09fb025477f7 100644
--- a/drivers/video/fbdev/hyperv_fb.c
+++ b/drivers/video/fbdev/hyperv_fb.c
@@ -952,7 +952,7 @@ static phys_addr_t hvfb_get_phymem(struct hv_device *hdev,
 }
 
 /* Release contiguous physical memory */
-static void hvfb_release_phymem(struct hv_device *hdev,
+static void hvfb_release_phymem(struct device *device,
 				phys_addr_t paddr, unsigned int size)
 {
 	unsigned int order = get_order(size);
@@ -960,7 +960,7 @@ static void hvfb_release_phymem(struct hv_device *hdev,
 	if (order <= MAX_PAGE_ORDER)
 		__free_pages(pfn_to_page(paddr >> PAGE_SHIFT), order);
 	else
-		dma_free_coherent(&hdev->device,
+		dma_free_coherent(device,
 				  round_up(size, PAGE_SIZE),
 				  phys_to_virt(paddr),
 				  paddr);
@@ -1074,7 +1074,7 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
 }
 
 /* Release the framebuffer */
-static void hvfb_putmem(struct hv_device *hdev, struct fb_info *info)
+static void hvfb_putmem(struct fb_info *info)
 {
 	struct hvfb_par *par = info->par;
 
@@ -1083,7 +1083,7 @@ static void hvfb_putmem(struct hv_device *hdev, struct fb_info *info)
 		iounmap(par->mmio_vp);
 		vmbus_free_mmio(par->mem->start, screen_fb_size);
 	} else {
-		hvfb_release_phymem(hdev, info->fix.smem_start,
+		hvfb_release_phymem(info->device, info->fix.smem_start,
 				    screen_fb_size);
 	}
 
@@ -1197,7 +1197,7 @@ static int hvfb_probe(struct hv_device *hdev,
 
 error:
 	fb_deferred_io_cleanup(info);
-	hvfb_putmem(hdev, info);
+	hvfb_putmem(info);
 error2:
 	vmbus_close(hdev->channel);
 error1:
@@ -1226,7 +1226,7 @@ static void hvfb_remove(struct hv_device *hdev)
 	vmbus_close(hdev->channel);
 	hv_set_drvdata(hdev, NULL);
 
-	hvfb_putmem(hdev, info);
+	hvfb_putmem(info);
 	framebuffer_release(info);
 }
 
-- 
2.43.0

RE: [PATCH v3 1/2] fbdev: hyperv_fb: Simplify hvfb_putmem

[Michael Kelley]

From: Saurabh Sengar <ssengar@linux.microsoft.com> Sent: Saturday, March 1, 2025 8:17 AM
> 
> The device object required in 'hvfb_release_phymem' function
> for 'dma_free_coherent' can also be obtained from the 'info'
> pointer, making 'hdev' parameter in 'hvfb_putmem' redundant.
> Remove the unnecessary 'hdev' argument from 'hvfb_putmem'.
> 
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> ---
>  drivers/video/fbdev/hyperv_fb.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
> index 363e4ccfcdb7..09fb025477f7 100644
> --- a/drivers/video/fbdev/hyperv_fb.c
> +++ b/drivers/video/fbdev/hyperv_fb.c
> @@ -952,7 +952,7 @@ static phys_addr_t hvfb_get_phymem(struct hv_device *hdev,
>  }
> 
>  /* Release contiguous physical memory */
> -static void hvfb_release_phymem(struct hv_device *hdev,
> +static void hvfb_release_phymem(struct device *device,
>  				phys_addr_t paddr, unsigned int size)
>  {
>  	unsigned int order = get_order(size);
> @@ -960,7 +960,7 @@ static void hvfb_release_phymem(struct hv_device *hdev,
>  	if (order <= MAX_PAGE_ORDER)
>  		__free_pages(pfn_to_page(paddr >> PAGE_SHIFT), order);
>  	else
> -		dma_free_coherent(&hdev->device,
> +		dma_free_coherent(device,
>  				  round_up(size, PAGE_SIZE),
>  				  phys_to_virt(paddr),
>  				  paddr);
> @@ -1074,7 +1074,7 @@ static int hvfb_getmem(struct hv_device *hdev, struct fb_info *info)
>  }
> 
>  /* Release the framebuffer */
> -static void hvfb_putmem(struct hv_device *hdev, struct fb_info *info)
> +static void hvfb_putmem(struct fb_info *info)
>  {
>  	struct hvfb_par *par = info->par;
> 
> @@ -1083,7 +1083,7 @@ static void hvfb_putmem(struct hv_device *hdev, struct fb_info *info)
>  		iounmap(par->mmio_vp);
>  		vmbus_free_mmio(par->mem->start, screen_fb_size);
>  	} else {
> -		hvfb_release_phymem(hdev, info->fix.smem_start,
> +		hvfb_release_phymem(info->device, info->fix.smem_start,
>  				    screen_fb_size);
>  	}
> 
> @@ -1197,7 +1197,7 @@ static int hvfb_probe(struct hv_device *hdev,
> 
>  error:
>  	fb_deferred_io_cleanup(info);
> -	hvfb_putmem(hdev, info);
> +	hvfb_putmem(info);
>  error2:
>  	vmbus_close(hdev->channel);
>  error1:
> @@ -1226,7 +1226,7 @@ static void hvfb_remove(struct hv_device *hdev)
>  	vmbus_close(hdev->channel);
>  	hv_set_drvdata(hdev, NULL);
> 
> -	hvfb_putmem(hdev, info);
> +	hvfb_putmem(info);
>  	framebuffer_release(info);
>  }
> 
> --
> 2.43.0

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>

[PATCH v3 2/2] fbdev: hyperv_fb: Allow graceful removal of framebuffer

[Saurabh Sengar]

When a Hyper-V framebuffer device is unbind, hyperv_fb driver tries to
release the framebuffer forcefully. If this framebuffer is in use it
produce the following WARN and hence this framebuffer is never released.

[   44.111220] WARNING: CPU: 35 PID: 1882 at drivers/video/fbdev/core/fb_info.c:70 framebuffer_release+0x2c/0x40
< snip >
[   44.111289] Call Trace:
[   44.111290]  <TASK>
[   44.111291]  ? show_regs+0x6c/0x80
[   44.111295]  ? __warn+0x8d/0x150
[   44.111298]  ? framebuffer_release+0x2c/0x40
[   44.111300]  ? report_bug+0x182/0x1b0
[   44.111303]  ? handle_bug+0x6e/0xb0
[   44.111306]  ? exc_invalid_op+0x18/0x80
[   44.111308]  ? asm_exc_invalid_op+0x1b/0x20
[   44.111311]  ? framebuffer_release+0x2c/0x40
[   44.111313]  ? hvfb_remove+0x86/0xa0 [hyperv_fb]
[   44.111315]  vmbus_remove+0x24/0x40 [hv_vmbus]
[   44.111323]  device_remove+0x40/0x80
[   44.111325]  device_release_driver_internal+0x20b/0x270
[   44.111327]  ? bus_find_device+0xb3/0xf0

Fix this by moving the release of framebuffer and assosiated memory
to fb_ops.fb_destroy function, so that framebuffer framework handles
it gracefully.

While we fix this, also replace manual registrations/unregistration of
framebuffer with devm_register_framebuffer.

Fixes: 68a2d20b79b1 ("drivers/video: add Hyper-V Synthetic Video Frame Buffer Driver")

Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
---
[V3]
 - using simplified hvfb_putmem()

 drivers/video/fbdev/hyperv_fb.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
index 09fb025477f7..76a42379c8df 100644
--- a/drivers/video/fbdev/hyperv_fb.c
+++ b/drivers/video/fbdev/hyperv_fb.c
@@ -282,6 +282,8 @@ static uint screen_depth;
 static uint screen_fb_size;
 static uint dio_fb_size; /* FB size for deferred IO */
 
+static void hvfb_putmem(struct fb_info *info);
+
 /* Send message to Hyper-V host */
 static inline int synthvid_send(struct hv_device *hdev,
 				struct synthvid_msg *msg)
@@ -862,6 +864,17 @@ static void hvfb_ops_damage_area(struct fb_info *info, u32 x, u32 y, u32 width,
 		hvfb_ondemand_refresh_throttle(par, x, y, width, height);
 }
 
+/*
+ * fb_ops.fb_destroy is called by the last put_fb_info() call at the end
+ * of unregister_framebuffer() or fb_release(). Do any cleanup related to
+ * framebuffer here.
+ */
+static void hvfb_destroy(struct fb_info *info)
+{
+	hvfb_putmem(info);
+	framebuffer_release(info);
+}
+
 /*
  * TODO: GEN1 codepaths allocate from system or DMA-able memory. Fix the
  *       driver to use the _SYSMEM_ or _DMAMEM_ helpers in these cases.
@@ -877,6 +890,7 @@ static const struct fb_ops hvfb_ops = {
 	.fb_set_par = hvfb_set_par,
 	.fb_setcolreg = hvfb_setcolreg,
 	.fb_blank = hvfb_blank,
+	.fb_destroy	= hvfb_destroy,
 };
 
 /* Get options from kernel paramenter "video=" */
@@ -1172,7 +1186,7 @@ static int hvfb_probe(struct hv_device *hdev,
 	if (ret)
 		goto error;
 
-	ret = register_framebuffer(info);
+	ret = devm_register_framebuffer(&hdev->device, info);
 	if (ret) {
 		pr_err("Unable to register framebuffer\n");
 		goto error;
@@ -1220,14 +1234,10 @@ static void hvfb_remove(struct hv_device *hdev)
 
 	fb_deferred_io_cleanup(info);
 
-	unregister_framebuffer(info);
 	cancel_delayed_work_sync(&par->dwork);
 
 	vmbus_close(hdev->channel);
 	hv_set_drvdata(hdev, NULL);
-
-	hvfb_putmem(info);
-	framebuffer_release(info);
 }
 
 static int hvfb_suspend(struct hv_device *hdev)
-- 
2.43.0

RE: [PATCH v3 2/2] fbdev: hyperv_fb: Allow graceful removal of framebuffer

[Michael Kelley]

From: Saurabh Sengar <ssengar@linux.microsoft.com> Sent: Saturday, March 1, 2025 8:17 AM
> 
> When a Hyper-V framebuffer device is unbind, hyperv_fb driver tries to
> release the framebuffer forcefully. If this framebuffer is in use it
> produce the following WARN and hence this framebuffer is never released.
> 
> [   44.111220] WARNING: CPU: 35 PID: 1882 at drivers/video/fbdev/core/fb_info.c:70
> framebuffer_release+0x2c/0x40
> < snip >
> [   44.111289] Call Trace:
> [   44.111290]  <TASK>
> [   44.111291]  ? show_regs+0x6c/0x80
> [   44.111295]  ? __warn+0x8d/0x150
> [   44.111298]  ? framebuffer_release+0x2c/0x40
> [   44.111300]  ? report_bug+0x182/0x1b0
> [   44.111303]  ? handle_bug+0x6e/0xb0
> [   44.111306]  ? exc_invalid_op+0x18/0x80
> [   44.111308]  ? asm_exc_invalid_op+0x1b/0x20
> [   44.111311]  ? framebuffer_release+0x2c/0x40
> [   44.111313]  ? hvfb_remove+0x86/0xa0 [hyperv_fb]
> [   44.111315]  vmbus_remove+0x24/0x40 [hv_vmbus]
> [   44.111323]  device_remove+0x40/0x80
> [   44.111325]  device_release_driver_internal+0x20b/0x270
> [   44.111327]  ? bus_find_device+0xb3/0xf0
> 
> Fix this by moving the release of framebuffer and assosiated memory
> to fb_ops.fb_destroy function, so that framebuffer framework handles
> it gracefully.
> 
> While we fix this, also replace manual registrations/unregistration of
> framebuffer with devm_register_framebuffer.
> 
> Fixes: 68a2d20b79b1 ("drivers/video: add Hyper-V Synthetic Video Frame Buffer Driver")
> 
> Signed-off-by: Saurabh Sengar <ssengar@linux.microsoft.com>
> ---
> [V3]
>  - using simplified hvfb_putmem()
> 
>  drivers/video/fbdev/hyperv_fb.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c
> index 09fb025477f7..76a42379c8df 100644
> --- a/drivers/video/fbdev/hyperv_fb.c
> +++ b/drivers/video/fbdev/hyperv_fb.c
> @@ -282,6 +282,8 @@ static uint screen_depth;
>  static uint screen_fb_size;
>  static uint dio_fb_size; /* FB size for deferred IO */
> 
> +static void hvfb_putmem(struct fb_info *info);
> +
>  /* Send message to Hyper-V host */
>  static inline int synthvid_send(struct hv_device *hdev,
>  				struct synthvid_msg *msg)
> @@ -862,6 +864,17 @@ static void hvfb_ops_damage_area(struct fb_info *info, u32 x, u32 y, u32 width,
>  		hvfb_ondemand_refresh_throttle(par, x, y, width, height);
>  }
> 
> +/*
> + * fb_ops.fb_destroy is called by the last put_fb_info() call at the end
> + * of unregister_framebuffer() or fb_release(). Do any cleanup related to
> + * framebuffer here.
> + */
> +static void hvfb_destroy(struct fb_info *info)
> +{
> +	hvfb_putmem(info);
> +	framebuffer_release(info);
> +}
> +
>  /*
>   * TODO: GEN1 codepaths allocate from system or DMA-able memory. Fix the
>   *       driver to use the _SYSMEM_ or _DMAMEM_ helpers in these cases.
> @@ -877,6 +890,7 @@ static const struct fb_ops hvfb_ops = {
>  	.fb_set_par = hvfb_set_par,
>  	.fb_setcolreg = hvfb_setcolreg,
>  	.fb_blank = hvfb_blank,
> +	.fb_destroy	= hvfb_destroy,
>  };
> 
>  /* Get options from kernel paramenter "video=" */
> @@ -1172,7 +1186,7 @@ static int hvfb_probe(struct hv_device *hdev,
>  	if (ret)
>  		goto error;
> 
> -	ret = register_framebuffer(info);
> +	ret = devm_register_framebuffer(&hdev->device, info);
>  	if (ret) {
>  		pr_err("Unable to register framebuffer\n");
>  		goto error;
> @@ -1220,14 +1234,10 @@ static void hvfb_remove(struct hv_device *hdev)
> 
>  	fb_deferred_io_cleanup(info);
> 
> -	unregister_framebuffer(info);
>  	cancel_delayed_work_sync(&par->dwork);
> 
>  	vmbus_close(hdev->channel);
>  	hv_set_drvdata(hdev, NULL);
> -
> -	hvfb_putmem(info);
> -	framebuffer_release(info);
>  }
> 
>  static int hvfb_suspend(struct hv_device *hdev)
> --
> 2.43.0

Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>

Re: [PATCH v3 0/2] fbdev: hyperv_fb: framebuffer release cleanup

[Wei Liu]

On Sat, Mar 01, 2025 at 08:16:29AM -0800, Saurabh Sengar wrote:
> This patch series addresses an issue in the unbind path of the hyperv_fb
> driver, which is resolved in the second patch of this series.
> 
> While working on this fix, it was observed that hvfb_putmem() and its
> child functions could be cleaned up first to simplify the movement of
> hvfb_putmem(). This cleanup is done in the first patch.
> 
> Although hvfb_getmem() could also be cleaned up, it depends on
> vmbus_allocate_mmio(), which is used by multiple other drivers. Since
> addressing hvfb_getmem() is independent of this fix, it will be handled
> in a separate patch series.
> 
> [V3]
>  - Add a patch 1 for cleanup of hvfb_putmem()
>  - Use the simplified hvfb_putmem()
> 
> Saurabh Sengar (2):
>   fbdev: hyperv_fb: Simplify hvfb_putmem
>   fbdev: hyperv_fb: Allow graceful removal of framebuffer

Applied to hyperv-fixes, thanks!