[U-Boot] [PATCH 1/1] efi_loader: remove efi_exit_caches()

[Peter Robinson]

> On 7/19/19 9:06 PM, Peter Robinson wrote:
> > On Fri, Jul 19, 2019 at 7:28 PM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> >>
> >> In GRUB before 2.04 a bug existed which did not allow booting some ARM32
> >> boards if U-Boot did not disable caches, cf.
> >> https://lists.linaro.org/pipermail/cross-distro/2019-July/000933.html
> >>
> >> In ExitBootServices() we were disabling the caches by calling
> >> cleanup_before_linux(). This workaround is not needed anymore.
> >
> > Do we want to remove this straight away? A lot of distributions will
> > take time to move to grub 2.04 because it's been a long time between
> > grub releases so they'll have quite a patch delta to re-align to the
> > new release. Fedora for example will rebase to grub 2.04 in Fedora 32
> > which will start development end of August but won't be released until
> > next year.
>
> As described below this code does not remove any functionality that was
> active in U-Boot v2019.04 or v2019.07.
>
> I can see nothing in https://fedoraproject.org/wiki/Updates_Policy
> stopping GRUB 2.04 from being made available for stable Fedora releases.

The maintainers believe that it's too intrusive to land now and they
want maximum testing time before it gets to stable users, funnily
enough people don't like it when their machines cease to boot.

> >> The UEFI spec requires that caches are enabled but architecturally defined
> >> caches should be disabled. But this requirement has to be fulfilled when
> >> invoking StartImage() and not after calling ExitBootServices(). So there is
> >> no reason for calling cleanup_before_linux() here.
> >>
> >> Since commit f69d63fae281 ("efi_loader: use efi_start_image() for
> >> bootefi"), i.e. v2019.04, we have not been calling efi_exit_caches()
> >> anymore which in turn would call cleanup_before_linux().
> >>
> >> Remove the obsolete function efi_exit_caches().
> >>
> >> Suggested-by: Alexander Graf <agraf at csgraf.de>
> >> Signed-off-by: Heinrich Schuchardt <xypron.glpk at gmx.de>
> >> ---
> >>  lib/efi_loader/efi_boottime.c | 28 ----------------------------
> >>  1 file changed, 28 deletions(-)
> >>
> >> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> >> index 4f6e8d1679..f84ee24416 100644
> >> --- a/lib/efi_loader/efi_boottime.c
> >> +++ b/lib/efi_loader/efi_boottime.c
> >> @@ -39,14 +39,6 @@ LIST_HEAD(efi_register_notify_events);
> >>  /* Handle of the currently executing image */
> >>  static efi_handle_t current_image;
> >>
> >> -/*
> >> - * If we're running on nasty systems (32bit ARM booting into non-EFI Linux)
> >> - * we need to do trickery with caches. Since we don't want to break the EFI
> >> - * aware boot path, only apply hacks when loading exiting directly (breaking
> >> - * direct Linux EFI booting along the way - oh well).
> >> - */
> >> -static bool efi_is_direct_boot = true;
> >> -
> >>  #ifdef CONFIG_ARM
> >>  /*
> >>   * The "gd" pointer lives in a register on ARM and AArch64 that we declare
> >> @@ -1906,21 +1898,6 @@ error:
> >>         return EFI_EXIT(ret);
> >>  }
> >>
> >> -/**
> >> - * efi_exit_caches() - fix up caches for EFI payloads if necessary
> >> - */
> >> -static void efi_exit_caches(void)
> >> -{
> >> -#if defined(CONFIG_ARM) && !defined(CONFIG_ARM64)
> >> -       /*
> >> -        * Grub on 32bit ARM needs to have caches disabled before jumping into
> >> -        * a zImage, but does not know of all cache layers. Give it a hand.
> >> -        */
> >> -       if (efi_is_direct_boot)
> >> -               cleanup_before_linux();
> >> -#endif
> >> -}
> >> -
> >>  /**
> >>   * efi_exit_boot_services() - stop all boot services
> >>   * @image_handle: handle of the loaded image
> >> @@ -1990,9 +1967,6 @@ static efi_status_t EFIAPI efi_exit_boot_services(efi_handle_t image_handle,
> >>         /* Patch out unsupported runtime function */
> >>         efi_runtime_detach();
> >>
> >> -       /* Fix up caches for EFI payloads if necessary */
> >> -       efi_exit_caches();
> >> -
> >>         /* This stops all lingering devices */
> >>         bootm_disable_interrupts();
> >>
> >> @@ -2893,8 +2867,6 @@ efi_status_t EFIAPI efi_start_image(efi_handle_t image_handle,
> >>         if (ret != EFI_SUCCESS)
> >>                 return EFI_EXIT(EFI_INVALID_PARAMETER);
> >>
> >> -       efi_is_direct_boot = false;
> >> -
> >>         image_obj->exit_data_size = exit_data_size;
> >>         image_obj->exit_data = exit_data;
> >>
> >> --
> >> 2.20.1
> >>
> >
>