On Wed, 17 Mar 2021 at 07:36, Shawn Guo <shawn.guo@xxxxxxxxxx> wrote: > > On Tue, Mar 16, 2021 at 10:33:17AM +0100, Ard Biesheuvel wrote: > > On Tue, 16 Mar 2021 at 10:06, Shawn Guo <shawn.guo@xxxxxxxxxx> wrote: > > > > > > On Tue, Mar 16, 2021 at 08:57:19AM +0100, Ard Biesheuvel wrote: > > > > On Tue, 16 Mar 2021 at 08:52, Shawn Guo <shawn.guo@xxxxxxxxxx> wrote: > > > > > > > > > > On Mon, Mar 15, 2021 at 02:07:01PM +0100, Ard Biesheuvel wrote: > > > > > > On Mon, 15 Mar 2021 at 04:11, Shawn Guo <shawn.guo@xxxxxxxxxx> 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@xxxxxxxxx> 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? > > > > > > > > > > Yes, with EFI variables runtime service marked as unsupported, > > > > > efibootmgr will just exit on efi_variables_supported() check [1] in > > > > > a way that its parent process, i.e. grub-install, doesn't take as an > > > > > error. But otherwise, efibootmgr will go much further and exit with > > > > > a real error when trying to access efivars. > > > > > > > > > > > > > OK, so I suggest we fix efibootmgr, by extending the > > > > efi_variables_supported() check to perform a GetVariable() call on an > > > > arbitrary variable (e.g., BootOrder), > > > > > > Hmm, I'm not sure we should ask more from user space, as it's already > > > been doing the right thing, and efi_variables_supported() is proved to > > > work properly with any sane low-level software (kernel + firmware), > > > either EFI variables service is supported or not. That said, IMHO, > > > right now the low-level software on Snapdragon laptops is insane, i.e. > > > the unsupported/broken EFI runtime services are not communicated to > > > user space properly in established way. > > > > > > > I disagree. > > > > My Yoga returns > > > > efivars: get_next_variable: status=8000000000000003 > > > > which is documented in the UEFI spec 2.8B section 8.2 as > > > > """ > > EFI_UNSUPPORTED > > After ExitBootServices() has been called, this return code may be > > returned if no variable storage is supported. The platform should > > describe this runtime service as unsupported at runtime via an > > EFI_RT_PROPERTIES_TABLE configuration table. > > """ > > > > No other condition is documented under which GetNextVariable() can > > return EFI_UNSUPPORTED, so it is perfectly suitable to decide whether > > the platform in question supports variable services at runtime at all. > > I'm not arguing against ideal of checking EFI_UNSUPPORTED. Instead, I > agree with that. What I'm arguing is that this should be done by kernel > rather than efibootmgr. The efi_variables_supported() of efibootmgr > checks EFIVARFS_MAGIC on /sys/firmware/efi/efivars. So if we have kernel > function efivar_init() check and respect EFI_UNSUPPORTED return and stop > right there, we are all good then. Could you take a look at the patch > attached and see if it's acceptable? > > Shawn > > ------8<--------------- > > From a30a9a03ed254e0f893b831618b30eaffe7f2da7 Mon Sep 17 00:00:00 2001 > From: Shawn Guo <shawn.guo@xxxxxxxxxx> > Date: Wed, 17 Mar 2021 11:57:58 +0800 > Subject: [PATCH] efivars: respect EFI_UNSUPPORTED return from firmware > > As per UEFI spec 2.8B section 8.2, EFI_UNSUPPORTED may be returned by > EFI variable runtime services if no variable storage is supported by > firmware. In this case, there is no point for kernel to continue > efivars initialization. That said, efivar_init() should fail by > returning an error code, so that efivarfs will not be mounted on > /sys/firmware/efi/efivars at all. Otherwise, user space like efibootmgr > will be confused by the EFIVARFS_MAGIC seen there, while EFI variable > calls cannot be made successfully. > > Signed-off-by: Shawn Guo <shawn.guo@xxxxxxxxxx> Yes, this makes sense. Acked-by: Ard Biesheuvel <ardb@xxxxxxxxxx> I'll queue this up > --- > drivers/firmware/efi/vars.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c > index 41c1d00bf933..abdc8a6a3963 100644 > --- a/drivers/firmware/efi/vars.c > +++ b/drivers/firmware/efi/vars.c > @@ -484,6 +484,10 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *), > } > } > > + break; > + case EFI_UNSUPPORTED: > + err = -EOPNOTSUPP; > + status = EFI_NOT_FOUND; > break; > case EFI_NOT_FOUND: > break; > -- > 2.17.1 >
