Re: [PATCH] efi: stub: override RT_PROP table supported mask based on EFI variable

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

On 3/15/21 2:07 PM, Ard Biesheuvel wrote:
> On Mon, 15 Mar 2021 at 04:11, Shawn Guo <shawn.guo@linaro.org> wrote:
>>
>> On Tue, Mar 09, 2021 at 07:47:25PM +0100, Ard Biesheuvel wrote:
>>> On Tue, 9 Mar 2021 at 19:10, Rob Clark <robdclark@gmail.com> wrote:
>>>>
> ...
>>>> fwiw, the valid use-case for ACPI boot on these things is for distro
>>>> installer.. it might not be the shiny accelerated experience, but you
>>>> want to be able to get thru the installer and then install updates to
>>>> get latest kernel/dtb/etc
>>>>
>>>> it is a small use-case, but kinda an important step ;-)
>>>>
>>>
>>> That is a fair point. However, as I understand it, we need this to work around
>>> - the need to pass efi=novamap
>>> - broken poweroff on Flex5g
>>
>> One more: broken EFI variable runtime services on all Snapdragon laptops
>>
>> It's been another pain of running debian-installer (d-i) on these
>> laptops, where EFI NV variables are just stored on UFS disk.  So after
>> Linux takes over the control of UFS, EFI NV variable runtime services
>> then become out of service.  Currently, we have to apply a hack [1] on
>> d-i grub-installer to get around the issue,  and it's been the only
>> remaining out-of-tree patch we have to carry for d-i.  With this nice
>> `OverrideSupported` support, we will be able to drop that hack
>> completely.
>>
>>>
>>> So an installer either needs to set the EFI variable, or pass
>>> efi=novamap on the first boot. Note that there are no arm64 EFI
>>> systems known where efi=novamap causes problems. In fact, I would
>>> prefer to stop using SetVirtualAddressMap() altogether, as it does not
>>> provide any benefit whatsoever. So perhaps we should make efi=novamap
>>> the default and be done with it.
>>>
>>> Broken poweroff is hardly a showstopper for an installer, given that
>>> we cannot even install GRUB correctly.
>>>
>>> In summary, I am more than happy to collaborate constructively on this
>>> (which is why I wrote the patch), but I don't think we're at a point
>>> yet where this is the only thing standing in our way when it comes to
>>> a smooth out-of-the-box Linux installation experience.
>>
>> There might be more to be done for getting a smooth Linux installation
>> experience.  But IMHO, this `OverrideSupported` thing is definitely
>> a big step to that.
>>
>
> So the problem here seems to be that grub-install (or efibootmgr)
> tolerates efivarfs being absent entirely, but bails out if it exists
> but gives an error when trying to access it, right?
>
> This is not only a problem on Snapdragon systems afaik - most Uboot
> based arm64 systems booting via EFI are affected by this as well.
>
> So it would be good if we could align with those folks, and maybe the
> ones working on RISC-V as well, to see if we can get some consensus
> around taking this approach.
>
> For the folks newly cc'ed on this thread: full version here
> https://lore.kernel.org/linux-arm-msm/20210306113519.294287-1-ardb@kernel.org/
>
> Note that I am both the author of the patch, and the maintainer
> pushing back on it. Please chime in if you think there are reasons why
> we want this, something like this or nothing like this.
>
Hello Ard,

looking at this thread it is hard to understand why this patch should be
needed.

If an UEFI application does not want to consume a service, it can do so
without having to manipulate the RT properties table.

Which UEFI applications are broken? Why can't they be fixed instead of
patching the kernel?

Can we have complete descriptions of the deficiencies of the involved
applications. I saw GRUB and the Debian installer mentioned in the
thread. Are there others?

Best regards

Heinrich