On Tue, 9 Mar 2021 at 04:22, Shawn Guo <shawn.guo@xxxxxxxxxx> wrote: > > On Mon, Mar 08, 2021 at 02:34:48PM +0100, Ard Biesheuvel wrote: > > On Sun, 7 Mar 2021 at 12:02, Shawn Guo <shawn.guo@xxxxxxxxxx> wrote: > > > > > > On Sat, Mar 06, 2021 at 12:35:19PM +0100, Ard Biesheuvel wrote: > > > > Allow EFI systems to override the set of supported runtime services > > > > declared via the RT_PROP table, by checking for the existence of a > > > > 'OverrideSupported' EFI variable of the appropriate size under the > > > > RT_PROP table GUID, and if it does, combine the supported mask using > > > > logical AND. (This means the override can only remove support, not > > > > add it back). > > > > > > > > Cc: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>, > > > > Cc: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> > > > > Cc: Shawn Guo <shawn.guo@xxxxxxxxxx> > > > > Cc: Rob Clark <robdclark@xxxxxxxxx> > > > > Cc: Leif Lindholm <leif@xxxxxxxxxxxx> > > > > Cc: linux-arm-msm@xxxxxxxxxxxxxxx > > > > > > > > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > > > > > Awesome, Ard! On both Lenovo Yoga C630 and Flex 5G latops: > > > > > > Tested-by: Shawn Guo <shawn.guo@xxxxxxxxxx> > > > > > > With 'OverrideSupported' EFI variable added from UEFI Shell, we can drop > > > 'efi=novamap' kernel cmdline and get around the broken poweroff runtime > > > services nicely. Thanks! > > > > > > > Thanks for confirming. > > > > However, I am not going to merge this without some justification, and > > hopefully some input from other folks (Leif?) > > > > RTPROP already provides what we need on all platforms that use > > DtbLoader, and the patch for that is queued up for v5.12-rcX, with a > > cc:stable to v5.10. This allows any RT service to be marked as > > disabled, including SetVirtualAddressMap(). > > > > So afaict, that means that this patch would be a special case for > > Flex5G, right? > > It's for all Snapdragon based laptops, as we need to disable > SetVirtualAddressMap runtime services on all of them. > > > So how are platforms such as this one going to load the > > DTB? If some loader will be involved (or even just GRUB), > > Yes, GRUB. > > > shouldn't it > > be that component that sets RTPROP like DtbLoader will, not the kernel > > itself. > > > > Btw I don't think ACPI boot is a use case here. I don't see a software > > framebuffer with no wifi support as a usage mode that justifies > > carrying EFI stub hacks for everyone. > > Okay. I'm fine to carry it as an out-of-tree patch until someday you > consider ACPI boot is useful for everyone. But I do boot these laptops > with ACPI at daily basis right now as arm64 native build machine, with > USB Ethernet adapter. > There may be several reasons why this patch might become worthwhile for upstream, but until that moment, I'd rather not merge it, as it will affect all users, including ones that boot with EFI secure boot enabled. (I haven't quite convinced myself that disabling runtime services arbitrarily using a EFI variable is not something that can be abused)
