On Tue, Jan 29, 2019 at 3:36 PM Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > > On Tue, 22 Jan 2019 at 16:06, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote: > > > > The bitmap left in the framebuffer by the firmware is described by an > > ACPI table called "BGRT", which describes the size, pixel format and > > the address of a BMP image in memory. While the BGRT ACPI table is > > guaranteed to reside in a "ACPI reclaim" memory region, which is > > never touched by Linux. The BMP image, however, typically resides > > in EFI Boot Services Memory, which may have been overwritten by the > > time the BGRT discovery routine runs. > > > > So instead, drop the handling from the ACPI init code, and call the > > BGRT parsing code immediately after going over the EFI configuration > > table array, at which time no memory has been touched yet except for > > the .data/.bss regions covered by the static kernel image. > > > > Unfortunately, this involves a non-trivial amount of ACPI entry > > point and root table parsing, but we cannot rely on the normal > > ACPI infrastructure yet this early in the boot. > > > > Also note that we cannot take the 'acpi_disabled' global variable > > into account, since it may not have assumed the correct value yet > > (on arm64, the default value is '1' which is overridden to '0' if > > no DT description has been made available by the firmware) > > > > Cc: Peter Jones <pjones@xxxxxxxxxx> > > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > > --- > > arch/arm64/kernel/acpi.c | 2 - > > arch/x86/kernel/acpi/boot.c | 2 - > > drivers/acpi/bgrt.c | 6 -- > > drivers/firmware/efi/efi-bgrt.c | 80 ++++++++++++++++++-- > > drivers/firmware/efi/efi.c | 13 ++++ > > include/linux/efi-bgrt.h | 4 +- > > 6 files changed, 89 insertions(+), 18 deletions(-) > > > > Rafael, Len, > > Do you mind if i take this via the EFI tree (after addressing > Lorenzo's comments) Not at all, please take it. Thanks!
