Re: [PATCH V3 1/4] efi/x86: move efi bgrt init code to early init code

[Dave Young <dyoung@redhat.com>]

On 01/19/17 at 12:48pm, Ard Biesheuvel wrote:
> On 18 January 2017 at 19:24, Bhupesh Sharma <bhsharma@redhat.com> wrote:
> > On Wed, Jan 18, 2017 at 7:30 PM, Ard Biesheuvel
> > <ard.biesheuvel@linaro.org> wrote:
> >> On 18 January 2017 at 13:48, Dave Young <dyoung@redhat.com> wrote:
> >>> Before invoking the arch specific handler, efi_mem_reserve() reserves
> >>> the given memory region through memblock.
> >>>
> >>> efi_bgrt_init will call efi_mem_reserve after mm_init(), at that time
> >>> memblock is dead and it should not be used any more.
> >>>
> >>> efi bgrt code depend on acpi intialization to get the bgrt acpi table,
> >>> moving bgrt parsing to acpi early boot code can make sure efi_mem_reserve
> >>> in efi bgrt code still use memblock safely.
> >>>
> >>> Signed-off-by: Dave Young <dyoung@redhat.com>
> >>
> >> This patch looks fine to me know
> >>
> >> Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >>
> >> but before applying it, I'd like
> >>
> >> - Bhupesh to confirm that this patch is a move in the right direction
> >> with regard to enabling BGRT on arm64/ACPI,
> >
> > I gave the changes from Dave a try on top of the following combination:
> > 4.10-rc3 + efi/next patches not available in 4.10-rc3 + Nicolai's patches
> >
> > and was able to get the BGRT table working properly with OVMF on a
> > QEMU-x86_64 machine. So you can add my tested-by for this patch
> > series.
> >
> > I think this is the right direction for the ARM64 BGRT handling
> > patches as well and I will post a RFC in two phases as suggested by
> > Ard, once Dave's patches are accepted (in efi/next?).
> >
> 
> Thanks!
> 
> >
> >> - an ack from the ACPI maintainers (cc'ed)
> >>
> 
> Rafael, Len? Any objections?


Ping..

> 
> If not, I will go ahead and queue this for v4.11

Ard, thanks, just ignore the last one 4/4 if you think it is risky or
unnecessary. 

> 
> 
> >>> --->>> v1->v2: efi_bgrt_init: check table length first before copying bgrt table
> >>>         error checking in drivers/acpi/bgrt.c
> >>> v2->v3: drop #ifdef added before; efi-bgrt.h build warning fix
> >>>         since only changed this patch, so I just only resend this one.
> >>>  arch/x86/kernel/acpi/boot.c      |    9 +++++
> >>>  arch/x86/platform/efi/efi-bgrt.c |   59 ++++++++++++++++-----------------------
> >>>  arch/x86/platform/efi/efi.c      |    5 ---
> >>>  drivers/acpi/bgrt.c              |   28 +++++++++++++-----
> >>>  include/linux/efi-bgrt.h         |   11 +++----
> >>>  init/main.c                      |    1
> >>>  6 files changed, 59 insertions(+), 54 deletions(-)
> >>>
> >>> --- linux-x86.orig/arch/x86/kernel/acpi/boot.c
> >>> +++ linux-x86/arch/x86/kernel/acpi/boot.c
> >>> @@ -35,6 +35,7 @@
> >>>  #include <linux/bootmem.h>
> >>>  #include <linux/ioport.h>
> >>>  #include <linux/pci.h>
> >>> +#include <linux/efi-bgrt.h>
> >>>
> >>>  #include <asm/irqdomain.h>
> >>>  #include <asm/pci_x86.h>
> >>> @@ -1557,6 +1558,12 @@ int __init early_acpi_boot_init(void)
> >>>         return 0;
> >>>  }
> >>>
> >>> +static int __init acpi_parse_bgrt(struct acpi_table_header *table)
> >>> +{
> >>> +       efi_bgrt_init(table);
> >>> +       return 0;
> >>> +}
> >>> +
> >>>  int __init acpi_boot_init(void)
> >>>  {
> >>>         /* those are executed after early-quirks are executed */
> >>> @@ -1581,6 +1588,8 @@ int __init acpi_boot_init(void)
> >>>         acpi_process_madt();
> >>>
> >>>         acpi_table_parse(ACPI_SIG_HPET, acpi_parse_hpet);
> >>> +       if (IS_ENABLED(CONFIG_ACPI_BGRT))
> >>> +               acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);
> >>>
> >>>         if (!acpi_noirq)
> >>>                 x86_init.pci.init = pci_acpi_init;
> >>> --- linux-x86.orig/arch/x86/platform/efi/efi-bgrt.c
> >>> +++ linux-x86/arch/x86/platform/efi/efi-bgrt.c
> >>> @@ -19,8 +19,7 @@
> >>>  #include <linux/efi.h>
> >>>  #include <linux/efi-bgrt.h>
> >>>
> >>> -struct acpi_table_bgrt *bgrt_tab;
> >>> -void *__initdata bgrt_image;
> >>> +struct acpi_table_bgrt bgrt_tab;
> >>>  size_t __initdata bgrt_image_size;
> >>>
> >>>  struct bmp_header {
> >>> @@ -28,66 +27,58 @@ struct bmp_header {
> >>>         u32 size;
> >>>  } __packed;
> >>>
> >>> -void __init efi_bgrt_init(void)
> >>> +void __init efi_bgrt_init(struct acpi_table_header *table)
> >>>  {
> >>> -       acpi_status status;
> >>>         void *image;
> >>>         struct bmp_header bmp_header;
> >>> +       struct acpi_table_bgrt *bgrt = &bgrt_tab;
> >>>
> >>>         if (acpi_disabled)
> >>>                 return;
> >>>
> >>> -       status = acpi_get_table("BGRT", 0,
> >>> -                               (struct acpi_table_header **)&bgrt_tab);
> >>> -       if (ACPI_FAILURE(status))
> >>> -               return;
> >>> -
> >>> -       if (bgrt_tab->header.length < sizeof(*bgrt_tab)) {
> >>> +       if (table->length < sizeof(bgrt_tab)) {
> >>>                 pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
> >>> -                      bgrt_tab->header.length, sizeof(*bgrt_tab));
> >>> +                      table->length, sizeof(bgrt_tab));
> >>>                 return;
> >>>         }
> >>> -       if (bgrt_tab->version != 1) {
> >>> +       *bgrt = *(struct acpi_table_bgrt *)table;
> >>> +       if (bgrt->version != 1) {
> >>>                 pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
> >>> -                      bgrt_tab->version);
> >>> -               return;
> >>> +                      bgrt->version);
> >>> +               goto out;
> >>>         }
> >>> -       if (bgrt_tab->status & 0xfe) {
> >>> +       if (bgrt->status & 0xfe) {
> >>>                 pr_notice("Ignoring BGRT: reserved status bits are non-zero %u\n",
> >>> -                      bgrt_tab->status);
> >>> -               return;
> >>> +                      bgrt->status);
> >>> +               goto out;
> >>>         }
> >>> -       if (bgrt_tab->image_type != 0) {
> >>> +       if (bgrt->image_type != 0) {
> >>>                 pr_notice("Ignoring BGRT: invalid image type %u (expected 0)\n",
> >>> -                      bgrt_tab->image_type);
> >>> -               return;
> >>> +                      bgrt->image_type);
> >>> +               goto out;
> >>>         }
> >>> -       if (!bgrt_tab->image_address) {
> >>> +       if (!bgrt->image_address) {
> >>>                 pr_notice("Ignoring BGRT: null image address\n");
> >>> -               return;
> >>> +               goto out;
> >>>         }
> >>>
> >>> -       image = memremap(bgrt_tab->image_address, sizeof(bmp_header), MEMREMAP_WB);
> >>> +       image = early_memremap(bgrt->image_address, sizeof(bmp_header));
> >>>         if (!image) {
> >>>                 pr_notice("Ignoring BGRT: failed to map image header memory\n");
> >>> -               return;
> >>> +               goto out;
> >>>         }
> >>>
> >>>         memcpy(&bmp_header, image, sizeof(bmp_header));
> >>> -       memunmap(image);
> >>> +       early_memunmap(image, sizeof(bmp_header));
> >>>         if (bmp_header.id != 0x4d42) {
> >>>                 pr_notice("Ignoring BGRT: Incorrect BMP magic number 0x%x (expected 0x4d42)\n",
> >>>                         bmp_header.id);
> >>> -               return;
> >>> +               goto out;
> >>>         }
> >>>         bgrt_image_size = bmp_header.size;
> >>> +       efi_mem_reserve(bgrt->image_address, bgrt_image_size);
> >>>
> >>> -       bgrt_image = memremap(bgrt_tab->image_address, bmp_header.size, MEMREMAP_WB);
> >>> -       if (!bgrt_image) {
> >>> -               pr_notice("Ignoring BGRT: failed to map image memory\n");
> >>> -               bgrt_image = NULL;
> >>> -               return;
> >>> -       }
> >>> -
> >>> -       efi_mem_reserve(bgrt_tab->image_address, bgrt_image_size);
> >>> +       return;
> >>> +out:
> >>> +       memset(bgrt, 0, sizeof(bgrt_tab));
> >>>  }
> >>> --- linux-x86.orig/drivers/acpi/bgrt.c
> >>> +++ linux-x86/drivers/acpi/bgrt.c
> >>> @@ -15,40 +15,41 @@
> >>>  #include <linux/sysfs.h>
> >>>  #include <linux/efi-bgrt.h>
> >>>
> >>> +static void *bgrt_image;
> >>>  static struct kobject *bgrt_kobj;
> >>>
> >>>  static ssize_t show_version(struct device *dev,
> >>>                             struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->version);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.version);
> >>>  }
> >>>  static DEVICE_ATTR(version, S_IRUGO, show_version, NULL);
> >>>
> >>>  static ssize_t show_status(struct device *dev,
> >>>                            struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->status);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.status);
> >>>  }
> >>>  static DEVICE_ATTR(status, S_IRUGO, show_status, NULL);
> >>>
> >>>  static ssize_t show_type(struct device *dev,
> >>>                          struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_type);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_type);
> >>>  }
> >>>  static DEVICE_ATTR(type, S_IRUGO, show_type, NULL);
> >>>
> >>>  static ssize_t show_xoffset(struct device *dev,
> >>>                             struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_offset_x);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_offset_x);
> >>>  }
> >>>  static DEVICE_ATTR(xoffset, S_IRUGO, show_xoffset, NULL);
> >>>
> >>>  static ssize_t show_yoffset(struct device *dev,
> >>>                             struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_offset_y);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_offset_y);
> >>>  }
> >>>  static DEVICE_ATTR(yoffset, S_IRUGO, show_yoffset, NULL);
> >>>
> >>> @@ -84,15 +85,24 @@ static int __init bgrt_init(void)
> >>>  {
> >>>         int ret;
> >>>
> >>> -       if (!bgrt_image)
> >>> +       if (!bgrt_tab.image_address)
> >>>                 return -ENODEV;
> >>>
> >>> +       bgrt_image = memremap(bgrt_tab.image_address, bgrt_image_size,
> >>> +                             MEMREMAP_WB);
> >>> +       if (!bgrt_image) {
> >>> +               pr_notice("Ignoring BGRT: failed to map image memory\n");
> >>> +               return -ENOMEM;
> >>> +       }
> >>> +
> >>>         bin_attr_image.private = bgrt_image;
> >>>         bin_attr_image.size = bgrt_image_size;
> >>>
> >>>         bgrt_kobj = kobject_create_and_add("bgrt", acpi_kobj);
> >>> -       if (!bgrt_kobj)
> >>> -               return -EINVAL;
> >>> +       if (!bgrt_kobj) {
> >>> +               ret = -EINVAL;
> >>> +               goto out_memmap;
> >>> +       }
> >>>
> >>>         ret = sysfs_create_group(bgrt_kobj, &bgrt_attribute_group);
> >>>         if (ret)
> >>> @@ -102,6 +112,8 @@ static int __init bgrt_init(void)
> >>>
> >>>  out_kobject:
> >>>         kobject_put(bgrt_kobj);
> >>> +out_memmap:
> >>> +       memunmap(bgrt_image);
> >>>         return ret;
> >>>  }
> >>>  device_initcall(bgrt_init);
> >>> --- linux-x86.orig/include/linux/efi-bgrt.h
> >>> +++ linux-x86/include/linux/efi-bgrt.h
> >>> @@ -1,20 +1,19 @@
> >>>  #ifndef _LINUX_EFI_BGRT_H
> >>>  #define _LINUX_EFI_BGRT_H
> >>>
> >>> -#ifdef CONFIG_ACPI_BGRT
> >>> -
> >>>  #include <linux/acpi.h>
> >>>
> >>> -void efi_bgrt_init(void);
> >>> +#ifdef CONFIG_ACPI_BGRT
> >>> +
> >>> +void efi_bgrt_init(struct acpi_table_header *table);
> >>>
> >>>  /* The BGRT data itself; only valid if bgrt_image != NULL. */
> >>> -extern void *bgrt_image;
> >>>  extern size_t bgrt_image_size;
> >>> -extern struct acpi_table_bgrt *bgrt_tab;
> >>> +extern struct acpi_table_bgrt bgrt_tab;
> >>>
> >>>  #else /* !CONFIG_ACPI_BGRT */
> >>>
> >>> -static inline void efi_bgrt_init(void) {}
> >>> +static inline void efi_bgrt_init(struct acpi_table_header *table) {}
> >>>
> >>>  #endif /* !CONFIG_ACPI_BGRT */
> >>>
> >>> --- linux-x86.orig/arch/x86/platform/efi/efi.c
> >>> +++ linux-x86/arch/x86/platform/efi/efi.c
> >>> @@ -542,11 +542,6 @@ void __init efi_init(void)
> >>>                 efi_print_memmap();
> >>>  }
> >>>
> >>> -void __init efi_late_init(void)
> >>> -{
> >>> -       efi_bgrt_init();
> >>> -}
> >>> -
> >>>  void __init efi_set_executable(efi_memory_desc_t *md, bool executable)
> >>>  {
> >>>         u64 addr, npages;
> >>> --- linux-x86.orig/init/main.c
> >>> +++ linux-x86/init/main.c
> >>> @@ -663,7 +663,6 @@ asmlinkage __visible void __init start_k
> >>>         sfi_init_late();
> >>>
> >>>         if (efi_enabled(EFI_RUNTIME_SERVICES)) {
> >>> -               efi_late_init();
> >>>                 efi_free_boot_services();
> >>>         }
> >>>
> 
> >> - an ack from the ACPI maintainers (cc'ed)
> >>
> >> Thanks,
> >> Ard.
> >>
> >>
> >>> ---
> >>> v1->v2: efi_bgrt_init: check table length first before copying bgrt table
> >>>         error checking in drivers/acpi/bgrt.c
> >>> v2->v3: drop #ifdef added before; efi-bgrt.h build warning fix
> >>>         since only changed this patch, so I just only resend this one.
> >>>  arch/x86/kernel/acpi/boot.c      |    9 +++++
> >>>  arch/x86/platform/efi/efi-bgrt.c |   59 ++++++++++++++++-----------------------
> >>>  arch/x86/platform/efi/efi.c      |    5 ---
> >>>  drivers/acpi/bgrt.c              |   28 +++++++++++++-----
> >>>  include/linux/efi-bgrt.h         |   11 +++----
> >>>  init/main.c                      |    1
> >>>  6 files changed, 59 insertions(+), 54 deletions(-)
> >>>
> >>> --- linux-x86.orig/arch/x86/kernel/acpi/boot.c
> >>> +++ linux-x86/arch/x86/kernel/acpi/boot.c
> >>> @@ -35,6 +35,7 @@
> >>>  #include <linux/bootmem.h>
> >>>  #include <linux/ioport.h>
> >>>  #include <linux/pci.h>
> >>> +#include <linux/efi-bgrt.h>
> >>>
> >>>  #include <asm/irqdomain.h>
> >>>  #include <asm/pci_x86.h>
> >>> @@ -1557,6 +1558,12 @@ int __init early_acpi_boot_init(void)
> >>>         return 0;
> >>>  }
> >>>
> >>> +static int __init acpi_parse_bgrt(struct acpi_table_header *table)
> >>> +{
> >>> +       efi_bgrt_init(table);
> >>> +       return 0;
> >>> +}
> >>> +
> >>>  int __init acpi_boot_init(void)
> >>>  {
> >>>         /* those are executed after early-quirks are executed */
> >>> @@ -1581,6 +1588,8 @@ int __init acpi_boot_init(void)
> >>>         acpi_process_madt();
> >>>
> >>>         acpi_table_parse(ACPI_SIG_HPET, acpi_parse_hpet);
> >>> +       if (IS_ENABLED(CONFIG_ACPI_BGRT))
> >>> +               acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);
> >>>
> >>>         if (!acpi_noirq)
> >>>                 x86_init.pci.init = pci_acpi_init;
> >>> --- linux-x86.orig/arch/x86/platform/efi/efi-bgrt.c
> >>> +++ linux-x86/arch/x86/platform/efi/efi-bgrt.c
> >>> @@ -19,8 +19,7 @@
> >>>  #include <linux/efi.h>
> >>>  #include <linux/efi-bgrt.h>
> >>>
> >>> -struct acpi_table_bgrt *bgrt_tab;
> >>> -void *__initdata bgrt_image;
> >>> +struct acpi_table_bgrt bgrt_tab;
> >>>  size_t __initdata bgrt_image_size;
> >>>
> >>>  struct bmp_header {
> >>> @@ -28,66 +27,58 @@ struct bmp_header {
> >>>         u32 size;
> >>>  } __packed;
> >>>
> >>> -void __init efi_bgrt_init(void)
> >>> +void __init efi_bgrt_init(struct acpi_table_header *table)
> >>>  {
> >>> -       acpi_status status;
> >>>         void *image;
> >>>         struct bmp_header bmp_header;
> >>> +       struct acpi_table_bgrt *bgrt = &bgrt_tab;
> >>>
> >>>         if (acpi_disabled)
> >>>                 return;
> >>>
> >>> -       status = acpi_get_table("BGRT", 0,
> >>> -                               (struct acpi_table_header **)&bgrt_tab);
> >>> -       if (ACPI_FAILURE(status))
> >>> -               return;
> >>> -
> >>> -       if (bgrt_tab->header.length < sizeof(*bgrt_tab)) {
> >>> +       if (table->length < sizeof(bgrt_tab)) {
> >>>                 pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
> >>> -                      bgrt_tab->header.length, sizeof(*bgrt_tab));
> >>> +                      table->length, sizeof(bgrt_tab));
> >>>                 return;
> >>>         }
> >>> -       if (bgrt_tab->version != 1) {
> >>> +       *bgrt = *(struct acpi_table_bgrt *)table;
> >>> +       if (bgrt->version != 1) {
> >>>                 pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
> >>> -                      bgrt_tab->version);
> >>> -               return;
> >>> +                      bgrt->version);
> >>> +               goto out;
> >>>         }
> >>> -       if (bgrt_tab->status & 0xfe) {
> >>> +       if (bgrt->status & 0xfe) {
> >>>                 pr_notice("Ignoring BGRT: reserved status bits are non-zero %u\n",
> >>> -                      bgrt_tab->status);
> >>> -               return;
> >>> +                      bgrt->status);
> >>> +               goto out;
> >>>         }
> >>> -       if (bgrt_tab->image_type != 0) {
> >>> +       if (bgrt->image_type != 0) {
> >>>                 pr_notice("Ignoring BGRT: invalid image type %u (expected 0)\n",
> >>> -                      bgrt_tab->image_type);
> >>> -               return;
> >>> +                      bgrt->image_type);
> >>> +               goto out;
> >>>         }
> >>> -       if (!bgrt_tab->image_address) {
> >>> +       if (!bgrt->image_address) {
> >>>                 pr_notice("Ignoring BGRT: null image address\n");
> >>> -               return;
> >>> +               goto out;
> >>>         }
> >>>
> >>> -       image = memremap(bgrt_tab->image_address, sizeof(bmp_header), MEMREMAP_WB);
> >>> +       image = early_memremap(bgrt->image_address, sizeof(bmp_header));
> >>>         if (!image) {
> >>>                 pr_notice("Ignoring BGRT: failed to map image header memory\n");
> >>> -               return;
> >>> +               goto out;
> >>>         }
> >>>
> >>>         memcpy(&bmp_header, image, sizeof(bmp_header));
> >>> -       memunmap(image);
> >>> +       early_memunmap(image, sizeof(bmp_header));
> >>>         if (bmp_header.id != 0x4d42) {
> >>>                 pr_notice("Ignoring BGRT: Incorrect BMP magic number 0x%x (expected 0x4d42)\n",
> >>>                         bmp_header.id);
> >>> -               return;
> >>> +               goto out;
> >>>         }
> >>>         bgrt_image_size = bmp_header.size;
> >>> +       efi_mem_reserve(bgrt->image_address, bgrt_image_size);
> >>>
> >>> -       bgrt_image = memremap(bgrt_tab->image_address, bmp_header.size, MEMREMAP_WB);
> >>> -       if (!bgrt_image) {
> >>> -               pr_notice("Ignoring BGRT: failed to map image memory\n");
> >>> -               bgrt_image = NULL;
> >>> -               return;
> >>> -       }
> >>> -
> >>> -       efi_mem_reserve(bgrt_tab->image_address, bgrt_image_size);
> >>> +       return;
> >>> +out:
> >>> +       memset(bgrt, 0, sizeof(bgrt_tab));
> >>>  }
> >>> --- linux-x86.orig/drivers/acpi/bgrt.c
> >>> +++ linux-x86/drivers/acpi/bgrt.c
> >>> @@ -15,40 +15,41 @@
> >>>  #include <linux/sysfs.h>
> >>>  #include <linux/efi-bgrt.h>
> >>>
> >>> +static void *bgrt_image;
> >>>  static struct kobject *bgrt_kobj;
> >>>
> >>>  static ssize_t show_version(struct device *dev,
> >>>                             struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->version);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.version);
> >>>  }
> >>>  static DEVICE_ATTR(version, S_IRUGO, show_version, NULL);
> >>>
> >>>  static ssize_t show_status(struct device *dev,
> >>>                            struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->status);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.status);
> >>>  }
> >>>  static DEVICE_ATTR(status, S_IRUGO, show_status, NULL);
> >>>
> >>>  static ssize_t show_type(struct device *dev,
> >>>                          struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_type);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_type);
> >>>  }
> >>>  static DEVICE_ATTR(type, S_IRUGO, show_type, NULL);
> >>>
> >>>  static ssize_t show_xoffset(struct device *dev,
> >>>                             struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_offset_x);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_offset_x);
> >>>  }
> >>>  static DEVICE_ATTR(xoffset, S_IRUGO, show_xoffset, NULL);
> >>>
> >>>  static ssize_t show_yoffset(struct device *dev,
> >>>                             struct device_attribute *attr, char *buf)
> >>>  {
> >>> -       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab->image_offset_y);
> >>> +       return snprintf(buf, PAGE_SIZE, "%d\n", bgrt_tab.image_offset_y);
> >>>  }
> >>>  static DEVICE_ATTR(yoffset, S_IRUGO, show_yoffset, NULL);
> >>>
> >>> @@ -84,15 +85,24 @@ static int __init bgrt_init(void)
> >>>  {
> >>>         int ret;
> >>>
> >>> -       if (!bgrt_image)
> >>> +       if (!bgrt_tab.image_address)
> >>>                 return -ENODEV;
> >>>
> >>> +       bgrt_image = memremap(bgrt_tab.image_address, bgrt_image_size,
> >>> +                             MEMREMAP_WB);
> >>> +       if (!bgrt_image) {
> >>> +               pr_notice("Ignoring BGRT: failed to map image memory\n");
> >>> +               return -ENOMEM;
> >>> +       }
> >>> +
> >>>         bin_attr_image.private = bgrt_image;
> >>>         bin_attr_image.size = bgrt_image_size;
> >>>
> >>>         bgrt_kobj = kobject_create_and_add("bgrt", acpi_kobj);
> >>> -       if (!bgrt_kobj)
> >>> -               return -EINVAL;
> >>> +       if (!bgrt_kobj) {
> >>> +               ret = -EINVAL;
> >>> +               goto out_memmap;
> >>> +       }
> >>>
> >>>         ret = sysfs_create_group(bgrt_kobj, &bgrt_attribute_group);
> >>>         if (ret)
> >>> @@ -102,6 +112,8 @@ static int __init bgrt_init(void)
> >>>
> >>>  out_kobject:
> >>>         kobject_put(bgrt_kobj);
> >>> +out_memmap:
> >>> +       memunmap(bgrt_image);
> >>>         return ret;
> >>>  }
> >>>  device_initcall(bgrt_init);
> >>> --- linux-x86.orig/include/linux/efi-bgrt.h
> >>> +++ linux-x86/include/linux/efi-bgrt.h
> >>> @@ -1,20 +1,19 @@
> >>>  #ifndef _LINUX_EFI_BGRT_H
> >>>  #define _LINUX_EFI_BGRT_H
> >>>
> >>> -#ifdef CONFIG_ACPI_BGRT
> >>> -
> >>>  #include <linux/acpi.h>
> >>>
> >>> -void efi_bgrt_init(void);
> >>> +#ifdef CONFIG_ACPI_BGRT
> >>> +
> >>> +void efi_bgrt_init(struct acpi_table_header *table);
> >>>
> >>>  /* The BGRT data itself; only valid if bgrt_image != NULL. */
> >>> -extern void *bgrt_image;
> >>>  extern size_t bgrt_image_size;
> >>> -extern struct acpi_table_bgrt *bgrt_tab;
> >>> +extern struct acpi_table_bgrt bgrt_tab;
> >>>
> >>>  #else /* !CONFIG_ACPI_BGRT */
> >>>
> >>> -static inline void efi_bgrt_init(void) {}
> >>> +static inline void efi_bgrt_init(struct acpi_table_header *table) {}
> >>>
> >>>  #endif /* !CONFIG_ACPI_BGRT */
> >>>
> >>> --- linux-x86.orig/arch/x86/platform/efi/efi.c
> >>> +++ linux-x86/arch/x86/platform/efi/efi.c
> >>> @@ -542,11 +542,6 @@ void __init efi_init(void)
> >>>                 efi_print_memmap();
> >>>  }
> >>>
> >>> -void __init efi_late_init(void)
> >>> -{
> >>> -       efi_bgrt_init();
> >>> -}
> >>> -
> >>>  void __init efi_set_executable(efi_memory_desc_t *md, bool executable)
> >>>  {
> >>>         u64 addr, npages;
> >>> --- linux-x86.orig/init/main.c
> >>> +++ linux-x86/init/main.c
> >>> @@ -663,7 +663,6 @@ asmlinkage __visible void __init start_k
> >>>         sfi_init_late();
> >>>
> >>>         if (efi_enabled(EFI_RUNTIME_SERVICES)) {
> >>> -               efi_late_init();
> >>>                 efi_free_boot_services();
> >>>         }
> >>>

Thanks
Dave