Re: [PATCH 8/8] fbdev/efifb: honour UEFI memory map attributes when mapping the fb

[James Hilliard <james.hilliard1@gmail.com>]

This patch appears to introduce a regression on my
system(https://www.jetwaycomputer.com/NF9B.html).
My board uses an Intel gma3650 GPU.
It causes a complete failure of all video output.
With it reverted I get:
[ 1.169444] efifb: probing for efifb
[ 1.169499] efifb: framebuffer at 0xcf800000, using 1876k, total 1875k
[ 1.169511] efifb: mode is 800x600x32, linelength=3200, pages=1
[ 1.169519] efifb: scrolling: redraw
[ 1.169528] efifb: Truecolor: size=8:8:8:8, shift=24:16:8:0
Without it reverted I get:
[ 1.173368] efifb: probing for efifb
[ 1.173386] efifb: abort, cannot remap video memory 0x1d5000 @ 0xcf800000
[ 1.173395] Trying to free nonexistent resource
<00000000cf800000-00000000cf9d4bff>
[ 1.173413] efi-framebuffer: probe of efi-framebuffer.0 failed with error -5

On Wed, Jul 11, 2018 at 11:40 AM Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
>
> If the framebuffer address provided by the Graphics Output Protocol
> (GOP) is covered by the UEFI memory map, it will tell us which memory
> attributes are permitted when mapping this region. In some cases,
> (KVM guest on ARM), violating this will result in loss of coherency,
> which means that updates sent to the framebuffer by the guest will
> not be observeable by the host, and the emulated display simply does
> not work.
>
> So if the memory map contains such a description, take the attributes
> field into account, and add support for creating WT or WB mappings of
> the framebuffer region.
>
> Cc: Peter Jones <pjones@redhat.com>
> Tested-by: Laszlo Ersek <lersek@redhat.com>
> Acked-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
>  drivers/video/fbdev/efifb.c | 51 +++++++++++++++++++++++++++++--------
>  1 file changed, 41 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index 46a4484e3da7..c6f78d27947b 100644
> --- a/drivers/video/fbdev/efifb.c
> +++ b/drivers/video/fbdev/efifb.c
> @@ -20,7 +20,7 @@
>  #include <drm/drm_connector.h>  /* For DRM_MODE_PANEL_ORIENTATION_* */
>
>  static bool request_mem_succeeded = false;
> -static bool nowc = false;
> +static u64 mem_flags = EFI_MEMORY_WC | EFI_MEMORY_UC;
>
>  static struct fb_var_screeninfo efifb_defined = {
>         .activate               = FB_ACTIVATE_NOW,
> @@ -68,8 +68,12 @@ static int efifb_setcolreg(unsigned regno, unsigned red, unsigned green,
>
>  static void efifb_destroy(struct fb_info *info)
>  {
> -       if (info->screen_base)
> -               iounmap(info->screen_base);
> +       if (info->screen_base) {
> +               if (mem_flags & (EFI_MEMORY_UC | EFI_MEMORY_WC))
> +                       iounmap(info->screen_base);
> +               else
> +                       memunmap(info->screen_base);
> +       }
>         if (request_mem_succeeded)
>                 release_mem_region(info->apertures->ranges[0].base,
>                                    info->apertures->ranges[0].size);
> @@ -104,7 +108,7 @@ static int efifb_setup(char *options)
>                         else if (!strncmp(this_opt, "width:", 6))
>                                 screen_info.lfb_width = simple_strtoul(this_opt+6, NULL, 0);
>                         else if (!strcmp(this_opt, "nowc"))
> -                               nowc = true;
> +                               mem_flags &= ~EFI_MEMORY_WC;
>                 }
>         }
>
> @@ -164,6 +168,7 @@ static int efifb_probe(struct platform_device *dev)
>         unsigned int size_remap;
>         unsigned int size_total;
>         char *option = NULL;
> +       efi_memory_desc_t md;
>
>         if (screen_info.orig_video_isVGA != VIDEO_TYPE_EFI || pci_dev_disabled)
>                 return -ENODEV;
> @@ -272,12 +277,35 @@ static int efifb_probe(struct platform_device *dev)
>         info->apertures->ranges[0].base = efifb_fix.smem_start;
>         info->apertures->ranges[0].size = size_remap;
>
> -       if (nowc)
> -               info->screen_base = ioremap(efifb_fix.smem_start, efifb_fix.smem_len);
> -       else
> -               info->screen_base = ioremap_wc(efifb_fix.smem_start, efifb_fix.smem_len);
> +       if (!efi_mem_desc_lookup(efifb_fix.smem_start, &md)) {
> +               if ((efifb_fix.smem_start + efifb_fix.smem_len) >
> +                   (md.phys_addr + (md.num_pages << EFI_PAGE_SHIFT))) {
> +                       pr_err("efifb: video memory @ 0x%lx spans multiple EFI memory regions\n",
> +                              efifb_fix.smem_start);
> +                       err = -EIO;
> +                       goto err_release_fb;
> +               }
> +               /*
> +                * If the UEFI memory map covers the efifb region, we may only
> +                * remap it using the attributes the memory map prescribes.
> +                */
> +               mem_flags |= EFI_MEMORY_WT | EFI_MEMORY_WB;
> +               mem_flags &= md.attribute;
> +       }
> +       if (mem_flags & EFI_MEMORY_WC)
> +               info->screen_base = ioremap_wc(efifb_fix.smem_start,
> +                                              efifb_fix.smem_len);
> +       else if (mem_flags & EFI_MEMORY_UC)
> +               info->screen_base = ioremap(efifb_fix.smem_start,
> +                                           efifb_fix.smem_len);
> +       else if (mem_flags & EFI_MEMORY_WT)
> +               info->screen_base = memremap(efifb_fix.smem_start,
> +                                            efifb_fix.smem_len, MEMREMAP_WT);
> +       else if (mem_flags & EFI_MEMORY_WB)
> +               info->screen_base = memremap(efifb_fix.smem_start,
> +                                            efifb_fix.smem_len, MEMREMAP_WB);
>         if (!info->screen_base) {
> -               pr_err("efifb: abort, cannot ioremap video memory 0x%x @ 0x%lx\n",
> +               pr_err("efifb: abort, cannot remap video memory 0x%x @ 0x%lx\n",
>                         efifb_fix.smem_len, efifb_fix.smem_start);
>                 err = -EIO;
>                 goto err_release_fb;
> @@ -371,7 +399,10 @@ static int efifb_probe(struct platform_device *dev)
>  err_groups:
>         sysfs_remove_groups(&dev->dev.kobj, efifb_groups);
>  err_unmap:
> -       iounmap(info->screen_base);
> +       if (mem_flags & (EFI_MEMORY_UC | EFI_MEMORY_WC))
> +               iounmap(info->screen_base);
> +       else
> +               memunmap(info->screen_base);
>  err_release_fb:
>         framebuffer_release(info);
>  err_release_mem:
> --
> 2.17.1
>
>
>
>