linux-kernel - Re: [PATCH 4.9 39/92] efi/arm: Revert deferred unmap of early memmap mapping

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Date:   Thu, 29 Nov 2018 15:28:44 +0100
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-efi <linux-efi@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, sashal@...nel.org
Subject: Re: [PATCH 4.9 39/92] efi/arm: Revert deferred unmap of early memmap mapping

On Thu, 29 Nov 2018 at 15:21, Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> 4.9-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> [ Upstream commit 33412b8673135b18ea42beb7f5117ed0091798b6 ]
>
> Commit:
>
>   3ea86495aef2 ("efi/arm: preserve early mapping of UEFI memory map longer for BGRT")
>
> deferred the unmap of the early mapping of the UEFI memory map to
> accommodate the ACPI BGRT code, which looks up the memory type that
> backs the BGRT table to validate it against the requirements of the UEFI spec.
>
> Unfortunately, this causes problems on ARM, which does not permit
> early mappings to persist after paging_init() is called, resulting
> in a WARN() splat. Since we don't support the BGRT table on ARM anway,
> let's revert ARM to the old behaviour, which is to take down the
> early mapping at the end of efi_init().
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: linux-efi@...r.kernel.org
> Fixes: 3ea86495aef2 ("efi/arm: preserve early mapping of UEFI memory ...")

This commit is only in v4.19 as far as I know. Does it even apply?


> Link: http://lkml.kernel.org/r/20181114175544.12860-3-ard.biesheuvel@linaro.org
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>  drivers/firmware/efi/arm-init.c    | 4 ++++
>  drivers/firmware/efi/arm-runtime.c | 2 +-
>  drivers/firmware/efi/memmap.c      | 3 +++
>  3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/firmware/efi/arm-init.c b/drivers/firmware/efi/arm-init.c
> index 1d1c9693ebfb..8ee91777abce 100644
> --- a/drivers/firmware/efi/arm-init.c
> +++ b/drivers/firmware/efi/arm-init.c
> @@ -256,6 +256,10 @@ void __init efi_init(void)
>                                     (params.mmap & ~PAGE_MASK)));
>
>         init_screen_info();
> +
> +       /* ARM does not permit early mappings to persist across paging_init() */
> +       if (IS_ENABLED(CONFIG_ARM))
> +               efi_memmap_unmap();
>  }
>
>  static int __init register_gop_device(void)
> diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c
> index 4d788e0debfe..069c5a4479e6 100644
> --- a/drivers/firmware/efi/arm-runtime.c
> +++ b/drivers/firmware/efi/arm-runtime.c
> @@ -118,7 +118,7 @@ static int __init arm_enable_runtime_services(void)
>  {
>         u64 mapsize;
>
> -       if (!efi_enabled(EFI_BOOT) || !efi_enabled(EFI_MEMMAP)) {
> +       if (!efi_enabled(EFI_BOOT)) {
>                 pr_info("EFI services will not be available.\n");
>                 return 0;
>         }
> diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
> index 78686443cb37..3fd2b450c649 100644
> --- a/drivers/firmware/efi/memmap.c
> +++ b/drivers/firmware/efi/memmap.c
> @@ -117,6 +117,9 @@ int __init efi_memmap_init_early(struct efi_memory_map_data *data)
>
>  void __init efi_memmap_unmap(void)
>  {
> +       if (!efi_enabled(EFI_MEMMAP))
> +               return;
> +
>         if (!efi.memmap.late) {
>                 unsigned long size;
>
> --
> 2.17.1
>
>
>