Commit 38ac0287 authored by Ard Biesheuvel's avatar Ard Biesheuvel Committed by Ingo Molnar
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fbdev/efifb: Honour UEFI memory map attributes when mapping the FB 



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.

Tested-by: default avatarLaszlo Ersek <lersek@redhat.com>
Signed-off-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: default avatarBartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Jones <pjones@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20180711094040.12506-9-ard.biesheuvel@linaro.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7e1550b8

drivers/video/fbdev/efifb.c

+41 −10
Original line number Diff line number Diff line
@@ -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)

	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 @@ err_fb_dealoc: 
err_groups:

	sysfs_remove_groups(&dev->dev.kobj, efifb_groups);

err_unmap:

	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:

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