Re: [PATCH] drm/fbdev-dma: fix getting smem_start

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Hi

Am 10.06.24 um 10:47 schrieb Thomas Zimmermann:
Hi

Am 04.06.24 um 10:03 schrieb Peng Fan (OSS):
From: Peng Fan <peng.fan@xxxxxxx>

If 'info->screen_buffer' locates in vmalloc address space, virt_to_page
will not be able to get correct results. With CONFIG_DEBUG_VM and
CONFIG_DEBUG_VIRTUAL enabled on ARM64, there is dump below:

Which graphics driver triggers this bug?

[    3.536043] ------------[ cut here ]------------
[    3.540716] virt_to_phys used for non-linear address: 000000007fc4f540 (0xffff800086001000) [    3.552628] WARNING: CPU: 4 PID: 61 at arch/arm64/mm/physaddr.c:12 __virt_to_phys+0x68/0x98
[    3.565455] Modules linked in:
[    3.568525] CPU: 4 PID: 61 Comm: kworker/u12:5 Not tainted 6.6.23-06226-g4986cc3e1b75-dirty #250
[    3.577310] Hardware name: NXP i.MX95 19X19 board (DT)
[    3.582452] Workqueue: events_unbound deferred_probe_work_func
[    3.588291] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[    3.595233] pc : __virt_to_phys+0x68/0x98
[    3.599246] lr : __virt_to_phys+0x68/0x98
[    3.603276] sp : ffff800083603990
[    3.677939] Call trace:
[    3.680393]  __virt_to_phys+0x68/0x98
[    3.684067]  drm_fbdev_dma_helper_fb_probe+0x138/0x238
[    3.689214] __drm_fb_helper_initial_config_and_unlock+0x2b0/0x4c0
[    3.695385]  drm_fb_helper_initial_config+0x4c/0x68
[    3.700264]  drm_fbdev_dma_client_hotplug+0x8c/0xe0
[    3.705161]  drm_client_register+0x60/0xb0
[    3.709269]  drm_fbdev_dma_setup+0x94/0x148

So add a check 'is_vmalloc_addr'.

Fixes: b79fe9abd58b ("drm/fbdev-dma: Implement fbdev emulation for GEM DMA helpers")
Signed-off-by: Peng Fan <peng.fan@xxxxxxx>

Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx>

I'm taking back my r-b. The memory is expected to by be physically contiguous and vmalloc() won't guarantee that.

Best regards
Thomas


Best regards
Thomas

---
  drivers/gpu/drm/drm_fbdev_dma.c | 7 ++++++-
  1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_fbdev_dma.c b/drivers/gpu/drm/drm_fbdev_dma.c
index 6c9427bb4053..9e2eddb6eb5c 100644
--- a/drivers/gpu/drm/drm_fbdev_dma.c
+++ b/drivers/gpu/drm/drm_fbdev_dma.c
@@ -130,7 +130,12 @@ static int drm_fbdev_dma_helper_fb_probe(struct drm_fb_helper *fb_helper,
          info->flags |= FBINFO_READS_FAST; /* signal caching */
      info->screen_size = sizes->surface_height * fb->pitches[0];
      info->screen_buffer = map.vaddr;
-    info->fix.smem_start = page_to_phys(virt_to_page(info->screen_buffer));
+
+    if (is_vmalloc_addr(info->screen_buffer))
+        info->fix.smem_start = page_to_phys(vmalloc_to_page(info->screen_buffer));
+    else
+        info->fix.smem_start = page_to_phys(virt_to_page(info->screen_buffer));
+
      info->fix.smem_len = info->screen_size;
        return 0;


--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)




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