linux-kernel - Re: [PATCH 1/2] UEFI arm64: add noefi boot param

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Message-ID: <20140806123958.GK25953@arm.com>
Date:	Wed, 6 Aug 2014 13:39:59 +0100
From:	Will Deacon <will.deacon@....com>
To:	Dave Young <dyoung@...hat.com>
Cc:	Catalin Marinas <Catalin.Marinas@....com>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"leif.lindholm@...aro.org" <leif.lindholm@...aro.org>,
	"ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
	"msalter@...hat.com" <msalter@...hat.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] UEFI arm64: add noefi boot param

On Wed, Aug 06, 2014 at 09:38:25AM +0100, Dave Young wrote:
> Adding a noefi boot param like in X86 to disable efi runtime services support.
> 
> This will be useful for debugging uefi problems. Also it will be useful
> for later kexec/kdump work. Kexec on uefi support in X86 depends on a fixed vm
> area specific for uefi runtime 1:1 mapping, kernel will switch to a different
> page table for any uefi runtime callback in virtual mode. In arm64 similar
> work probably is necessary. But kexec boot will just works with 'noefi' with
> the limitaion of lacking runtime services. The runtime services is not critical
> for kdump kernel for now. So as for kexec/kdump just leave the 1:1 mapping a
> future work.
> 
> Signed-off-by: Dave Young <dyoung@...hat.com>

This looks fine to me, but I'd like Leif's ack before I merge it. Leif?

Will

> ---
>  arch/arm64/kernel/efi.c |   17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> Index: linux-2.6/arch/arm64/kernel/efi.c
> ===================================================================
> --- linux-2.6.orig/arch/arm64/kernel/efi.c
> +++ linux-2.6/arch/arm64/kernel/efi.c
> @@ -31,6 +31,14 @@ static efi_runtime_services_t *runtime;
>  
>  static u64 efi_system_table;
>  
> +static bool disable_runtime __initdata = false;
> +static int __init setup_noefi(char *arg)
> +{
> +	disable_runtime = true;
> +	return 0;
> +}
> +early_param("noefi", setup_noefi);
> +
>  static int uefi_debug __initdata;
>  static int __init uefi_debug_setup(char *str)
>  {
> @@ -391,11 +399,14 @@ static int __init arm64_enter_virtual_mo
>  		return -1;
>  	}
>  
> -	pr_info("Remapping and enabling EFI services.\n");
> -
> -	/* replace early memmap mapping with permanent mapping */
>  	mapsize = memmap.map_end - memmap.map;
>  	early_memunmap(memmap.map, mapsize);
> +
> +	if (disable_runtime)
> +		return -ENODEV;
> +
> +	pr_info("Remapping and enabling EFI services.\n");
> +	/* replace early memmap mapping with permanent mapping */
>  	memmap.map = (__force void *)ioremap_cache((phys_addr_t)memmap.phys_map,
>  						   mapsize);
>  	memmap.map_end = memmap.map + mapsize;
> 
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