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Date: Fri, 9 Sep 2016 19:34:42 +0200
From: Borislav Petkov <bp@alien8.de>
To: Tom Lendacky <thomas.lendacky@amd.com>
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Subject: Re: [RFC PATCH v2 13/20] x86: Decrypt trampoline area if memory
 encryption is active
Message-ID: <20160909173442.wypsprnzb5ax6xqb@pd.tnic>
References: <20160822223529.29880.50884.stgit@tlendack-t1.amdoffice.net>
 <20160822223757.29880.24107.stgit@tlendack-t1.amdoffice.net>
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On Mon, Aug 22, 2016 at 05:37:57PM -0500, Tom Lendacky wrote:
> When Secure Memory Encryption is enabled, the trampoline area must not
> be encrypted. A cpu running in real mode will not be able to decrypt

s/cpu/CPU/... always :-)

> memory that has been encrypted because it will not be able to use addresses
> with the memory encryption mask.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  arch/x86/realmode/init.c |    9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
> index 5db706f1..f74925f 100644
> --- a/arch/x86/realmode/init.c
> +++ b/arch/x86/realmode/init.c
> @@ -6,6 +6,7 @@
>  #include <asm/pgtable.h>
>  #include <asm/realmode.h>
>  #include <asm/tlbflush.h>
> +#include <asm/mem_encrypt.h>
>  
>  struct real_mode_header *real_mode_header;
>  u32 *trampoline_cr4_features;
> @@ -130,6 +131,14 @@ static void __init set_real_mode_permissions(void)
>  	unsigned long text_start =
>  		(unsigned long) __va(real_mode_header->text_start);
>  
> +	/*
> +	 * If memory encryption is active, the trampoline area will need to
> +	 * be in non-encrypted memory in order to bring up other processors

Let's stick with either "unencrypted" - I'd prefer that one - or
"non-encrypted" nomenclature so that there's no distraction. I see both
versions in the patchset.

-- 
Regards/Gruss,
    Boris.

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