tree a04a6bf14e83387e36341ff38a975debf57852b7
parent ffce430d2b65d508a1604dc986ba16db3583943d
author Ard Biesheuvel <ardb@kernel.org> 1718636861 +0200
committer mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> 1718743976 +0000

OvmfPkg/QemuVideoDxe: add feature PCD to remap framebuffer W/C

Some platforms (such as SBSA-QEMU on recent builds of the emulator) only
tolerate misaligned accesses to normal memory, and raise alignment
faults on such accesses to device memory, which is the default for PCIe
MMIO BARs.

When emulating a PCIe graphics controller, the framebuffer is typically
exposed via a MMIO BAR, while the disposition of the region is closer to
memory (no side effects on reads or writes, except for the changing
picture on the screen; direct random access to any pixel in the image).

In order to permit the use of such controllers on platforms that only
tolerate these types of accesses for normal memory, it is necessary to
remap the memory. Use the DXE services to set the desired capabilities
and attributes.

Hide this behavior under a feature PCD so only platforms that really
need it can enable it. (OVMF on x86 has no need for this)

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>