,On 22 June 2018 at 09:52, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> 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: linux-fbdev@xxxxxxxxxxxxxxx
> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
> Cc: Peter Jones <pjones@xxxxxxxxxx>
> Tested-by: Laszlo Ersek <lersek@xxxxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Bartlomiej, do you have any comments on this patch? If not, I would
like to queue it in the efi tree.
Thanks,
Ard.
> ---
> drivers/video/fbdev/efifb.c | 52 ++++++++++++++++----
> 1 file changed, 42 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index 46a4484e3da7..d5e0a74e6124 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_WT | EFI_MEMORY_WB))
> + memunmap(info->screen_base);
> + else
> + iounmap(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 +168,8 @@ 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 +278,35 @@ 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 +400,10 @@ 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_WT | EFI_MEMORY_WB))
> + memunmap(info->screen_base);
> + else
> + iounmap(info->screen_base);
> err_release_fb:
> framebuffer_release(info);
> err_release_mem:
> --
> 2.17.1
>
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