Re: [PATCH v2 3/4] efi/arm: map UEFI memory map earlier on boot

[Will Deacon]

On Thu, Jul 05, 2018 at 12:02:15PM +0100, James Morse wrote:
> On 05/07/18 10:43, AKASHI Takahiro wrote:
> > On Wed, Jul 04, 2018 at 08:49:32PM +0200, Ard Biesheuvel wrote:
> >> On 4 July 2018 at 19:06, Will Deacon <will.deacon@xxxxxxx> wrote:
> >>> On Tue, Jun 19, 2018 at 03:44:23PM +0900, AKASHI Takahiro wrote:
> >>>> Since arm_enter_runtime_services() was modified to always create a virtual
> >>>> mapping of UEFI memory map in the previous patch, it is now renamed to
> >>>> efi_enter_virtual_mode() and called earlier before acpi_load_tables()
> >>>> in acpi_early_init().
> >>>>
> >>>> This will allow us to use UEFI memory map in acpi_os_ioremap() to create
> >>>> mappings of ACPI tables using memory attributes described in UEFI memory
> >>>> map.
> 
> >>> Hmm, this is ugly as hell. Is there nothing else we can piggy-back off?
> >>> It's also fairly jarring that, on x86, efi_enter_virtual_mode() is called
> >>> a few lines later, *after* acpi_early_init() has been called.
> 
> >> Currently, there is a gap where we have already torn down the early
> >> mapping and haven't created the definitive mapping of the UEFI memory
> >> map. There are other reasons why this is an issue, and I recently
> >> proposed [0] myself to address one of them
> 
> >> Akashi-san, could you please confirm whether the patch below would be
> >> sufficient for you? Apologies for going back and forth on this, but I
> >> agree with Will that we should try to avoid warts like the one above
> >> in generic code.
> >>
> >> [0] https://marc.info/?l=linux-efi&m=152930773507524&w=2
> > 
> > I think that this patch will also work.
> > Please drop my patch#2 and #3 if you want to pick up my patchset, Will.
> 
> Patch 2 is what changes arm_enable_runtime_services() to map the efi memory map
> before bailing out due to efi=noruntime.
> 
> Without it, 'efi=noruntime' means no-acpi-tables.

So it sounds like we want patch 2. Akashi, given that this series is only
four patches, please can you send out a v3 with the stuff that should be
reviewed and merged? Otherwise, there's a real risk we end up with breakage
that goes unnoticed initially.

Thanks,

Will