Re: [RFC PATCH v1 15/18] x86: Enable memory encryption on the APs

[Tom Lendacky]

On 05/01/2016 05:10 PM, Huang, Kai wrote:
> 
> 
> On 4/27/2016 10:58 AM, Tom Lendacky wrote:
>> Add support to set the memory encryption enable flag on the APs during
>> realmode initialization. When an AP is started it checks this flag, and
>> if set, enables memory encryption on its core.
>>
>> Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
>> ---
>>  arch/x86/include/asm/msr-index.h     |    2 ++
>>  arch/x86/include/asm/realmode.h      |   12 ++++++++++++
>>  arch/x86/realmode/init.c             |    4 ++++
>>  arch/x86/realmode/rm/trampoline_64.S |   14 ++++++++++++++
>>  4 files changed, 32 insertions(+)
>>
>> diff --git a/arch/x86/include/asm/msr-index.h
>> b/arch/x86/include/asm/msr-index.h
>> index 94555b4..b73182b 100644
>> --- a/arch/x86/include/asm/msr-index.h
>> +++ b/arch/x86/include/asm/msr-index.h
>> @@ -349,6 +349,8 @@
>>  #define MSR_K8_TOP_MEM1            0xc001001a
>>  #define MSR_K8_TOP_MEM2            0xc001001d
>>  #define MSR_K8_SYSCFG            0xc0010010
>> +#define MSR_K8_SYSCFG_MEM_ENCRYPT_BIT    23
>> +#define MSR_K8_SYSCFG_MEM_ENCRYPT    (1ULL <<
>> MSR_K8_SYSCFG_MEM_ENCRYPT_BIT)
>>  #define MSR_K8_INT_PENDING_MSG        0xc0010055
>>  /* C1E active bits in int pending message */
>>  #define K8_INTP_C1E_ACTIVE_MASK        0x18000000
>> diff --git a/arch/x86/include/asm/realmode.h
>> b/arch/x86/include/asm/realmode.h
>> index 9c6b890..e24d2ec 100644
>> --- a/arch/x86/include/asm/realmode.h
>> +++ b/arch/x86/include/asm/realmode.h
>> @@ -1,6 +1,15 @@
>>  #ifndef _ARCH_X86_REALMODE_H
>>  #define _ARCH_X86_REALMODE_H
>>
>> +/*
>> + * Flag bit definitions for use with the flags field of the
>> trampoline header
>> + * when configured for X86_64
>> + */
>> +#define TH_FLAGS_MEM_ENCRYPT_BIT    0
>> +#define TH_FLAGS_MEM_ENCRYPT        (1ULL << TH_FLAGS_MEM_ENCRYPT_BIT)
> 
> Would mind change it to a more vendor specific name, such as
> AMD_MEM_ENCRYPT, or SME_MEM_ENCRYPT?

Yup, that can be done.

> 
>> +
>> +#ifndef __ASSEMBLY__
>> +
>>  #include <linux/types.h>
>>  #include <asm/io.h>
>>
>> @@ -38,6 +47,7 @@ struct trampoline_header {
>>      u64 start;
>>      u64 efer;
>>      u32 cr4;
>> +    u32 flags;
>>  #endif
>>  };
>>
>> @@ -61,4 +71,6 @@ extern unsigned char secondary_startup_64[];
>>  void reserve_real_mode(void);
>>  void setup_real_mode(void);
>>
>> +#endif /* __ASSEMBLY__ */
>> +
>>  #endif /* _ARCH_X86_REALMODE_H */
>> diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c
>> index 85b145c..657532b 100644
>> --- a/arch/x86/realmode/init.c
>> +++ b/arch/x86/realmode/init.c
>> @@ -84,6 +84,10 @@ void __init setup_real_mode(void)
>>      trampoline_cr4_features = &trampoline_header->cr4;
>>      *trampoline_cr4_features = __read_cr4();
>>
>> +    trampoline_header->flags = 0;
>> +    if (sme_me_mask)
>> +        trampoline_header->flags |= TH_FLAGS_MEM_ENCRYPT;
>> +
>>      trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd);
>>      trampoline_pgd[0] = init_level4_pgt[pgd_index(__PAGE_OFFSET)].pgd;
>>      trampoline_pgd[511] = init_level4_pgt[511].pgd;
>> diff --git a/arch/x86/realmode/rm/trampoline_64.S
>> b/arch/x86/realmode/rm/trampoline_64.S
>> index dac7b20..8d84167 100644
>> --- a/arch/x86/realmode/rm/trampoline_64.S
>> +++ b/arch/x86/realmode/rm/trampoline_64.S
>> @@ -30,6 +30,7 @@
>>  #include <asm/msr.h>
>>  #include <asm/segment.h>
>>  #include <asm/processor-flags.h>
>> +#include <asm/realmode.h>
>>  #include "realmode.h"
>>
>>      .text
>> @@ -109,6 +110,18 @@ ENTRY(startup_32)
>>      movl    $(X86_CR0_PG | X86_CR0_WP | X86_CR0_PE), %eax
>>      movl    %eax, %cr0
>>
>> +    # Check for and enable memory encryption support
>> +    movl    pa_tr_flags, %eax
>> +    bt    $TH_FLAGS_MEM_ENCRYPT_BIT, pa_tr_flags
> 
> pa_tr_flags -> %eax ? Otherwise looks the previous line is useless.

Yes, I overlooked that. I'll take care of it.

Thanks,
Tom

> 
> Thanks,
> -Kai
> 
>> +    jnc    .Ldone
>> +    movl    $MSR_K8_SYSCFG, %ecx
>> +    rdmsr
>> +    bt    $MSR_K8_SYSCFG_MEM_ENCRYPT_BIT, %eax
>> +    jc    .Ldone
>> +    bts    $MSR_K8_SYSCFG_MEM_ENCRYPT_BIT, %eax
>> +    wrmsr
>> +.Ldone:
>> +
>>      /*
>>       * At this point we're in long mode but in 32bit compatibility mode
>>       * with EFER.LME = 1, CS.L = 0, CS.D = 1 (and in turn
>> @@ -147,6 +160,7 @@ GLOBAL(trampoline_header)
>>      tr_start:        .space    8
>>      GLOBAL(tr_efer)        .space    8
>>      GLOBAL(tr_cr4)        .space    4
>> +    GLOBAL(tr_flags)    .space    4
>>  END(trampoline_header)
>>
>>  #include "trampoline_common.S"
>>
>>