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SubjectRe: [PATCH v9 04/38] x86/CPU/AMD: Add the Secure Memory Encryption CPU feature
On Fri, Jul 7, 2017 at 9:38 AM, Tom Lendacky <thomas.lendacky@amd.com> wrote:
> Update the CPU features to include identifying and reporting on the
> Secure Memory Encryption (SME) feature. SME is identified by CPUID
> 0x8000001f, but requires BIOS support to enable it (set bit 23 of
> MSR_K8_SYSCFG). Only show the SME feature as available if reported by
> CPUID and enabled by BIOS.
>
> Reviewed-by: Borislav Petkov <bp@suse.de>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> arch/x86/include/asm/cpufeatures.h | 1 +
> arch/x86/include/asm/msr-index.h | 2 ++
> arch/x86/kernel/cpu/amd.c | 13 +++++++++++++
> arch/x86/kernel/cpu/scattered.c | 1 +
> 4 files changed, 17 insertions(+)
>
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 2701e5f..2b692df 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -196,6 +196,7 @@
>
> #define X86_FEATURE_HW_PSTATE ( 7*32+ 8) /* AMD HW-PState */
> #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */
> +#define X86_FEATURE_SME ( 7*32+10) /* AMD Secure Memory Encryption */

Given that this feature is available only in long mode, this should be
added to disabled-features.h as disabled for 32-bit builds.

> #define X86_FEATURE_INTEL_PPIN ( 7*32+14) /* Intel Processor Inventory Number */
> #define X86_FEATURE_INTEL_PT ( 7*32+15) /* Intel Processor Trace */
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index 18b1623..460ac01 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -352,6 +352,8 @@
> #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 BIT_ULL(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/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index bb5abe8..c47ceee 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -611,6 +611,19 @@ static void early_init_amd(struct cpuinfo_x86 *c)
> */
> if (cpu_has_amd_erratum(c, amd_erratum_400))
> set_cpu_bug(c, X86_BUG_AMD_E400);
> +
> + /*
> + * BIOS support is required for SME. If BIOS has not enabled SME
> + * then don't advertise the feature (set in scattered.c)
> + */
> + if (cpu_has(c, X86_FEATURE_SME)) {
> + u64 msr;
> +
> + /* Check if SME is enabled */
> + rdmsrl(MSR_K8_SYSCFG, msr);
> + if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT))
> + clear_cpu_cap(c, X86_FEATURE_SME);
> + }

This should be conditional on CONFIG_X86_64.

> }
>
> static void init_amd_k8(struct cpuinfo_x86 *c)
> diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
> index 23c2350..05459ad 100644
> --- a/arch/x86/kernel/cpu/scattered.c
> +++ b/arch/x86/kernel/cpu/scattered.c
> @@ -31,6 +31,7 @@ struct cpuid_bit {
> { X86_FEATURE_HW_PSTATE, CPUID_EDX, 7, 0x80000007, 0 },
> { X86_FEATURE_CPB, CPUID_EDX, 9, 0x80000007, 0 },
> { X86_FEATURE_PROC_FEEDBACK, CPUID_EDX, 11, 0x80000007, 0 },
> + { X86_FEATURE_SME, CPUID_EAX, 0, 0x8000001f, 0 },

This should also be conditional. We don't want to set this feature on
32-bit, even if the processor has support.

> { 0, 0, 0, 0, 0 }
> };

--
Brian Gerst

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