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SubjectRe: [RFC PATCH v3 12/20] x86: Decrypt trampoline area if memory encryption is active
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On 11/17/2016 12:09 PM, Borislav Petkov wrote:
> On Wed, Nov 09, 2016 at 06:37:08PM -0600, 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
>> 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..44ed32a 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 un-encrypted memory in order to bring up other processors
>> + * successfully.
>> + */
>> + sme_early_mem_dec(__pa(base), size);
>> + sme_set_mem_unenc(base, size);
>
> We're still unsure about the non-encrypted state: dec vs unenc. Please
> unify those for ease of use, code reading, etc etc.
>
> sme_early_decrypt(__pa(base), size);
> sme_mark_decrypted(base, size);
>
> or similar looks much more readable and understandable to me.

Yeah, I'll go through and change everything so that the implication
or action is expressed better.

Thanks,
Tom

>

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