Re: [PATCH v4 18/38] fbdev: defio: assert FBINFO_VIRTFB, drop VM_IO, add VM_MIXEDMAP
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From: Suren Baghdasaryan <surenb@google.com>
Date: 2026-10-04 18:02:17
Also in:
bpf, fuse-devel, kvm, kvm-riscv, kvmarm, linux-arch, linux-doc, linux-fbdev, linux-fsdevel, linux-mm, linux-perf-users, linux-rdma, linux-riscv, linux-s390, linux-scsi, linux-sound, linux-trace-kernel, linux-usb, lkml, selinux, sparclinux
On Sat, Oct 3, 2026 at 6:39 PM Lorenzo Stoakes (ARM) [off-list ref] wrote:
Currently all drivers which use defio allocate system memory. All of them
also set FBINFO_VIRTFB, other than ssd1307fb, however this driver allocates
system RAM, so simply failed to set this flag when it ought to.
This patch sets FBINFO_VIRTFB on ssd1307fb probe, then drops setting VM_IO
in fb_deferred_io_mmap() and instead requires FBINFO_VIRTFB to be set,
erroring out with a kernel warning if not.
The logic requires a page from the driver and since commit 1ecbc7dd2902
("fbdev/deferred-io: Always call get_page() for framebuffer pages") has
always required it to be refcounted, so this was implicitly already the
case.
Finally this patch sets VM_MIXEDMAP, as the logic is mapping
kernel-allocated memory so this is appropriate.
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>With the same disclaimer as in previous patch, Reviewed-by: Suren Baghdasaryan <surenb@google.com>
quoted hunk ↗ jump to hunk
--- drivers/video/fbdev/core/fb_defio.c | 6 +++--- drivers/video/fbdev/ssd1307fb.c | 2 ++ 2 files changed, 5 insertions(+), 3 deletions(-)diff --git a/drivers/video/fbdev/core/fb_defio.c b/drivers/video/fbdev/core/fb_defio.c index fd00b86e1ae6..fb359ecc3966 100644 --- a/drivers/video/fbdev/core/fb_defio.c +++ b/drivers/video/fbdev/core/fb_defio.c@@ -366,13 +366,13 @@ int fb_deferred_io_mmap(struct fb_info *info, struct vm_area_struct *vma) { vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot); + if (WARN_ON_ONCE(!(info->flags & FBINFO_VIRTFB))) + return -EINVAL; if (!try_module_get(THIS_MODULE)) return -EINVAL; vma->vm_ops = &fb_deferred_io_vm_ops; - vm_flags_set(vma, VM_DONTEXPAND | VM_DONTDUMP); - if (!(info->flags & FBINFO_VIRTFB)) - vm_flags_set(vma, VM_IO); + vm_flags_set(vma, VM_MIXEDMAP | VM_DONTEXPAND | VM_DONTDUMP); vma->vm_private_data = info->fbdefio_state; fb_deferred_io_state_get(info->fbdefio_state); /* released in vma->vm_ops->close() */diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c index c4fdecafd856..958514a35433 100644 --- a/drivers/video/fbdev/ssd1307fb.c +++ b/drivers/video/fbdev/ssd1307fb.c@@ -763,6 +763,8 @@ static int ssd1307fb_probe(struct i2c_client *client) info->fix.smem_start = __pa(vmem); info->fix.smem_len = vmem_size; + info->flags = FBINFO_VIRTFB; + fb_deferred_io_init(info); i2c_set_clientdata(client, info); --2.55.0