Re: [PATCH] fbdev: efifb: do not load efifb if PCI BAR has changed but not fixuped

Signed-off-by: Shixiong Ou <redacted>
---
  drivers/video/fbdev/efifb.c     |  4 ++++
  drivers/video/screen_info_pci.c | 24 ++++++++++++++++++++++++
  include/linux/screen_info.h     |  5 +++++
  3 files changed, 33 insertions(+)

diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
index 0e1bd3dba255..de8d016c9a66 100644
--- a/drivers/video/fbdev/efifb.c
+++ b/drivers/video/fbdev/efifb.c

@@ -303,6 +303,10 @@ static void efifb_setup(struct screen_info *si, char *options)
  
  static inline bool fb_base_is_valid(struct screen_info *si)
  {
+	/* check whether fb_base has changed but not fixuped */
+	if (!screen_info_is_useful())
+		return false;
+
  	if (si->lfb_base)
  		return true;
  

diff --git a/drivers/video/screen_info_pci.c b/drivers/video/screen_info_pci.c
index 66bfc1d0a6dc..ac57dcaf0cac 100644
--- a/drivers/video/screen_info_pci.c
+++ b/drivers/video/screen_info_pci.c

@@ -9,6 +9,8 @@ static struct pci_dev *screen_info_lfb_pdev;
  static size_t screen_info_lfb_bar;
  static resource_size_t screen_info_lfb_res_start; // original start of resource
  static resource_size_t screen_info_lfb_offset; // framebuffer offset within resource
+static bool screen_info_changed;
+static bool screen_info_fixuped;
  
  static bool __screen_info_relocation_is_valid(const struct screen_info *si, struct resource *pr)
  {

@@ -24,6 +26,24 @@ static bool __screen_info_relocation_is_valid(const struct screen_info *si, stru
  	return true;
  }
  
+bool screen_info_is_useful(void)
+{
+	unsigned int type;
+	const struct screen_info *si = &screen_info;
+
+	type = screen_info_video_type(si);
+	if (type != VIDEO_TYPE_EFI)
+		return true;
+
+	if (screen_info_changed && !screen_info_fixuped) {
+		pr_warn("The screen_info has changed but not fixuped");
+		return false;
+	}
+
+	pr_info("The screen_info is useful");
+	return true;
+}
+
  void screen_info_apply_fixups(void)
  {
  	struct screen_info *si = &screen_info;

@@ -32,18 +52,22 @@ void screen_info_apply_fixups(void)
  		struct resource *pr = &screen_info_lfb_pdev->resource[screen_info_lfb_bar];
  
  		if (pr->start != screen_info_lfb_res_start) {
+			screen_info_changed = true;
  			if (__screen_info_relocation_is_valid(si, pr)) {
  				/*
  				 * Only update base if we have an actual
  				 * relocation to a valid I/O range.
  				 */
  				__screen_info_set_lfb_base(si, pr->start + screen_info_lfb_offset);
+				screen_info_fixuped = true;
  				pr_info("Relocating firmware framebuffer to offset %pa[d] within %pr\n",
  					&screen_info_lfb_offset, pr);
  			} else {
  				pr_warn("Invalid relocating, disabling firmware framebuffer\n");
  			}
  		}
+	} else {
+		screen_info_changed = true;
  	}
  }
  

diff --git a/include/linux/screen_info.h b/include/linux/screen_info.h
index 923d68e07679..632cdbb1adbe 100644
--- a/include/linux/screen_info.h
+++ b/include/linux/screen_info.h

@@ -138,9 +138,14 @@ ssize_t screen_info_resources(const struct screen_info *si, struct resource *r,
  u32 __screen_info_lfb_bits_per_pixel(const struct screen_info *si);
  
  #if defined(CONFIG_PCI)
+bool screen_info_is_useful(void);
  void screen_info_apply_fixups(void);
  struct pci_dev *screen_info_pci_dev(const struct screen_info *si);
  #else
+bool screen_info_is_useful(void)
+{
+	return true;
+}
  static inline void screen_info_apply_fixups(void)
  { }
  static inline struct pci_dev *screen_info_pci_dev(const struct screen_info *si)