On 2018-06-25 04:20, Ard Biesheuvel wrote:

On 22 June 2018 at 21:29, Ard Biesheuvel [off-list ref] 
wrote:

quoted

On 22 June 2018 at 20:30, Sinan Kaya [off-list ref] wrote:

quoted

On 6/22/2018 2:01 PM, Ard Biesheuvel wrote:

quoted

quoted

Yes, it is part of the PCI I/O protocol definition. FrameBufferBase 
is
described as

"""
Base address of graphics linear frame buffer. Info contains
information required to allow software to draw directly to the
frame buffer without using Blt().Offset zero in
FrameBufferBase represents the upper left pixel of the
display.
"""

I just tried AMD Radeon and NVidia graphics cards on a system with
non-1:1 mapped MMIO windows, and in both cases, the GOP protocol
structure is populated correctly, i.e., using the CPU address not 
the
PCIe address.

EDK2 only recently gained support for MMIO translation in the host
bridge driver, so I so wonder if this is a platform issue rather 
than
a driver issue. It may be worth a try to dump the results of
GetBarAttributes() of all PCI I/O protocol instances (either in UEFI
or in the stub), to double check that the correct values are 
returned.

Thanks for checking out other platforms. I'll mark the issue as a 
BIOS
issue and bounce your feedback to the BIOS provider.

I screwed up my testing, unfortunately. Both the public AMD GOP driver
I tried, and the Nvidia GT218 under x86 emulation break when using
MMIO translation. However, GraphicsOutputDxe in the EDK2 tree gets it
right, and uses PciIo->GetBarAttributes() to get the address of the
framebuffer region, which will return the CPU address not the PCI
address.

quoted

Let's hold onto this patch for the moment.

Yes. I'd like to get this resolved as well, but if the drivers are
dereferencing BAR values as CPU addresses, this is unlikely to be the
only thing that is broken under outbound translation.

Note that this was fixed fairly recently in EDK2, so BIOS vendors
providing UEFI firmware for ARM platforms with outbound MMIO
translation should probably incorporate this EDK2 patch

commit dc080d3b61e570e7a3163fc24afa6f8388d0c0bf
Author: Heyi Guo [off-list ref]
Date:   Thu Feb 8 11:13:27 2018 +0800

    MdeModulePkg/PciBus: return CPU address for GetBarAttributes

    According to UEFI spec 2.7, PciIo->GetBarAttributes should return 
host
    address (CPU view ddress) rather than device address (PCI view
    address), and
    device address = host address + address translation offset,
    so we subtract translation from device address before returning.

Note that this is not the only MMIO translation related change made by
Heyi Guo to the generic PCI host bridge and bus drivers, but given
that those did not support MMIO translation at all, I take it your
affected platforms will already have their own changes to accommodate
this.

Platform has been doing mmio translation for quite a while. Because all 
accesses go through pci io protocol, the rest of the UEFI never needed 
to be aware of bar address or do direct access.

This is the first time I hear of direct access. Maybe, GOP is a special 
case.

I started copying your response to the bios vendor.

They are probably missing that patch. I will pass it along.