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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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