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

[Peter Robinson]

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.

> 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
>