[PATCH v5 0/6] RISC-V DT related fixes for reserved memory & UEFI

Ard Biesheuvel ard.biesheuvel at linaro.org
Tue Apr 7 08:51:18 CEST 2020

On Tue, 7 Apr 2020 at 08:46, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> On 4/6/20 11:01 PM, Ard Biesheuvel wrote:
> > On Mon, 6 Apr 2020 at 22:45, Atish Patra <atish.patra at wdc.com> wrote:
> >>
> >> This series adds few DT related fixes required for Linux EFI stub to work
> >> on RISC-V.
> >>
> >
> > I'm not sure how this is supposed to work, since DT reserved memory
> > regions are not used by EFI. If you want to reserve memory on a UEFI
> > system, you have to reserve it in the UEFI memory map from firmware.
> > The DT reserved-memory node is taken into account too late, the
> > /memreserve/ entries are ignored entirely.
> Hello Ard,
> thanks for reviewing.
> What do you mean by "The DT reserved-memory node is taken into account
> too late"?
> Cf. commit 7be64b885a36 ("cmd: bootefi: Parse reserved-memory node from DT")

What I mean is that the EFI stub in Linux uses memory allocation
functions, expecting the firmware to ensure that those allocations do
not conflict with memory descriptions and reservations in DT. So if
the firmware wants to express this redundantly, by passing
reservations in both reserved-memory and in the EFI memory map, that
is probably fine.

Also, I must sheepishly admit that I only realize now that this patch
set is against u-boot not Linux :-)

So if fixed reserved-memory regions are only being used to seed the
reserved regions in the EFI memory map, you can safely ignore me.
Apologies for the noise.

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