118 lines
4.1 KiB
Diff
118 lines
4.1 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Thomas Zimmermann <tzimmermann@suse.de>
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Date: Tue, 25 Jan 2022 10:12:18 +0100
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Subject: [PATCH] fbdev: Hot-unplug firmware fb devices on forced removal
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Hot-unplug all firmware-framebuffer devices as part of removing
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them via remove_conflicting_framebuffers() et al. Releases all
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memory regions to be acquired by native drivers.
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Firmware, such as EFI, install a framebuffer while posting the
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computer. After removing the firmware-framebuffer device from fbdev,
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a native driver takes over the hardware and the firmware framebuffer
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becomes invalid.
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Firmware-framebuffer drivers, specifically simplefb, don't release
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their device from Linux' device hierarchy. It still owns the firmware
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framebuffer and blocks the native drivers from loading. This has been
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observed in the vmwgfx driver. [1]
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Initiating a device removal (i.e., hot unplug) as part of
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remove_conflicting_framebuffers() removes the underlying device and
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returns the memory range to the system.
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[1] https://lore.kernel.org/dri-devel/20220117180359.18114-1-zack@kde.org/
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v2:
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* rename variable 'dev' to 'device' (Javier)
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Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
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Reported-by: Zack Rusin <zackr@vmware.com>
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Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
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Reviewed-by: Zack Rusin <zackr@vmware.com>
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CC: stable@vger.kernel.org # v5.11+
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Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
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---
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drivers/video/fbdev/core/fbmem.c | 29 ++++++++++++++++++++++++++---
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include/linux/fb.h | 1 +
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2 files changed, 27 insertions(+), 3 deletions(-)
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diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
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index 7bd5e2a4a9da..91145d93990a 100644
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--- a/drivers/video/fbdev/core/fbmem.c
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+++ b/drivers/video/fbdev/core/fbmem.c
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@@ -25,6 +25,7 @@
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#include <linux/init.h>
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#include <linux/linux_logo.h>
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#include <linux/proc_fs.h>
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+#include <linux/platform_device.h>
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#include <linux/seq_file.h>
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#include <linux/console.h>
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#include <linux/kmod.h>
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@@ -1557,18 +1558,36 @@ static void do_remove_conflicting_framebuffers(struct apertures_struct *a,
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/* check all firmware fbs and kick off if the base addr overlaps */
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for_each_registered_fb(i) {
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struct apertures_struct *gen_aper;
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+ struct device *device;
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if (!(registered_fb[i]->flags & FBINFO_MISC_FIRMWARE))
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continue;
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gen_aper = registered_fb[i]->apertures;
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+ device = registered_fb[i]->device;
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if (fb_do_apertures_overlap(gen_aper, a) ||
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(primary && gen_aper && gen_aper->count &&
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gen_aper->ranges[0].base == VGA_FB_PHYS)) {
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printk(KERN_INFO "fb%d: switching to %s from %s\n",
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i, name, registered_fb[i]->fix.id);
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- do_unregister_framebuffer(registered_fb[i]);
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+
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+ /*
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+ * If we kick-out a firmware driver, we also want to remove
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+ * the underlying platform device, such as simple-framebuffer,
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+ * VESA, EFI, etc. A native driver will then be able to
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+ * allocate the memory range.
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+ *
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+ * If it's not a platform device, at least print a warning. A
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+ * fix would add code to remove the device from the system.
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+ */
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+ if (dev_is_platform(device)) {
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+ registered_fb[i]->forced_out = true;
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+ platform_device_unregister(to_platform_device(device));
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+ } else {
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+ pr_warn("fb%d: cannot remove device\n", i);
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+ do_unregister_framebuffer(registered_fb[i]);
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+ }
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}
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}
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}
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@@ -1895,9 +1914,13 @@ EXPORT_SYMBOL(register_framebuffer);
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void
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unregister_framebuffer(struct fb_info *fb_info)
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{
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- mutex_lock(®istration_lock);
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+ bool forced_out = fb_info->forced_out;
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+
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+ if (!forced_out)
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+ mutex_lock(®istration_lock);
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do_unregister_framebuffer(fb_info);
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- mutex_unlock(®istration_lock);
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+ if (!forced_out)
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+ mutex_unlock(®istration_lock);
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}
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EXPORT_SYMBOL(unregister_framebuffer);
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diff --git a/include/linux/fb.h b/include/linux/fb.h
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index 02f362c661c8..3d7306c9a706 100644
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--- a/include/linux/fb.h
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+++ b/include/linux/fb.h
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@@ -502,6 +502,7 @@ struct fb_info {
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} *apertures;
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bool skip_vt_switch; /* no VT switch on suspend/resume required */
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+ bool forced_out; /* set when being removed by another driver */
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};
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static inline struct apertures_struct *alloc_apertures(unsigned int max_num) {
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