On Tue, 23 Apr 2019 at 17:01, James Hilliard <james.hilliard1@xxxxxxxxx> wrote:
>
> 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.
Thanks James, I will add your tested-by.
I forgot to include EFI_MEMORY_UC in the first mask, so I will respin
and resend.
Ingo, Bartlomiej, may i suggest that we take this into tip directly as
a fix? 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
> >
