From: Ard Biesheuvel ard.biesheuvel@linaro.org
commit f8585539df0a1527c78b5d760665c89fe1c105a9 upstream.
The following 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@gmail.com Tested-by: James Hilliard james.hilliard1@gmail.com Signed-off-by: Ard Biesheuvel ard.biesheuvel@linaro.org Cc: stable@vger.kernel.org # v4.19+ Cc: Borislav Petkov bp@alien8.de Cc: James Morse james.morse@arm.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Matt Fleming matt@codeblueprint.co.uk Cc: Peter Jones pjones@redhat.com Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Cc: linux-efi@vger.kernel.org Fixes: 38ac0287b7f4 ("fbdev/efifb: Honour UEFI memory map attributes when ...") Link: http://lkml.kernel.org/r/20190516213159.3530-2-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/video/fbdev/efifb.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-)
--- a/drivers/video/fbdev/efifb.c +++ b/drivers/video/fbdev/efifb.c @@ -476,8 +476,12 @@ static int efifb_probe(struct platform_d * 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_UC | 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,