ACK: [PATCH 1/1][SRU Cosmic][SRU Bionic] efi/arm: Revert deferred unmap of early memmap mapping

[Stefan Bader]

On 21.12.18 19:52, dann frazier wrote:
> From: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> 
> BugLink: https://bugs.launchpad.net/bugs/1809488
> 
> 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 at linaro.org>
> Cc: Linus Torvalds <torvalds at linux-foundation.org>
> Cc: Peter Zijlstra <peterz at infradead.org>
> Cc: Thomas Gleixner <tglx at linutronix.de>
> Cc: linux-efi at vger.kernel.org
> Fixes: 3ea86495aef2 ("efi/arm: preserve early mapping of UEFI memory ...")
> Link: http://lkml.kernel.org/r/20181114175544.12860-3-ard.biesheuvel@linaro.org
> Signed-off-by: Ingo Molnar <mingo at kernel.org>
> (cherry picked from commit 33412b8673135b18ea42beb7f5117ed0091798b6)
> Signed-off-by: dann frazier <dann.frazier at canonical.com>
Acked-by: Stefan Bader <stefan.bader at canonical.com>
> ---
>  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 388a929baf95d..1a6a77df8a5e8 100644
> --- a/drivers/firmware/efi/arm-init.c
> +++ b/drivers/firmware/efi/arm-init.c
> @@ -265,6 +265,10 @@ 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 922cfb813109a..a00934d263c51 100644
> --- a/drivers/firmware/efi/arm-runtime.c
> +++ b/drivers/firmware/efi/arm-runtime.c
> @@ -110,7 +110,7 @@ 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 5fc70520e04c4..1907db2b38d81 100644
> --- a/drivers/firmware/efi/memmap.c
> +++ b/drivers/firmware/efi/memmap.c
> @@ -118,6 +118,9 @@ 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;
>  
> 


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