On Tue, Apr 23, 2019 at 4:44 PM Ard Biesheuvel
<ard.biesheuvel@xxxxxxxxxx> wrote:
>
> Commit 38ac0287b7f4
>
> ("fbdev/efifb: Honour UEFI memory map attributes when mapping the FB")
>
> updated the EFI framebuffer code to use memory mappings for the linear
> framebuffer that are permitted by the memory attributes described by the
> EFI memory map for the particular region, if the framebuffer happens to
> be covered by the EFI memory map (which is typically only the case for
> framebuffers in shared memory). This is required since non-X86 systems
> may require cacheable attributes for memory mappings that are shared
> with other masters (such as GPUs), and this information cannot be
> described by the Graphics Output Protocol (GOP) EFI protocol itself,
> and so we rely on the EFI memory map for this.
>
> As reported by James, this breaks some x86 systems:
>
> [ 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
>
> The problem turns out to be that the memory map entry that describes the
> framebuffer has no memory attributes listed at all, and so we end up with
> a mem_flags value of 0x0.
>
> So work around this by ensuring that the memory map entry's attribute field
> has a sane value before using it to mask the set of usable attributes.
>
> Reported-by: James Hilliard <james.hilliard1@xxxxxxxxx>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
>
> James, could you give this a try please? Thanks.
I can confirm this fixes the regression on my system, thanks.
>
> drivers/video/fbdev/efifb.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
> index ba906876cc45..1f9949f50900 100644
> --- a/drivers/video/fbdev/efifb.c
> +++ b/drivers/video/fbdev/efifb.c
> @@ -476,8 +476,11 @@ static int efifb_probe(struct platform_device *dev)
> * 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;
> + md.attribute &= EFI_MEMORY_WC | EFI_MEMORY_WT | EFI_MEMORY_WB;
> + if (md.attribute) {
> + 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,
> --
> 2.20.1
>
