linux-kernel - Re: [PATCH v36 02/24] x86/cpufeatures: x86/msr: Add Intel SGX Launch Control hardware bits

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Date:   Thu, 06 Aug 2020 14:14:06 +0100
From:   Darren Kenny <darren.kenny@...cle.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>, x86@...nel.org,
        linux-sgx@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Jethro Beekman <jethro@...tanix.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, cedric.xing@...el.com, chenalexchen@...gle.com,
        conradparker@...gle.com, cyhanish@...gle.com,
        dave.hansen@...el.com, haitao.huang@...el.com,
        josh@...htriplett.org, kai.huang@...el.com, kai.svahn@...el.com,
        kmoy@...gle.com, ludloff@...gle.com, luto@...nel.org,
        nhorman@...hat.com, npmccallum@...hat.com, puiterwijk@...hat.com,
        rientjes@...gle.com, tglx@...utronix.de, yaozhangx@...gle.com
Subject: Re: [PATCH v36 02/24] x86/cpufeatures: x86/msr: Add Intel SGX
 Launch Control hardware bits

On Thursday, 2020-07-16 at 16:52:41 +03, Jarkko Sakkinen wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
>
> Add X86_FEATURE_SGX_LC, which informs whether or not the CPU supports SGX
> Launch Control.
>
> Add MSR_IA32_SGXLEPUBKEYHASH{0, 1, 2, 3}, which when combined contain a
> SHA256 hash of a 3072-bit RSA public key. SGX backed software packages, so
> called enclaves, are always signed. All enclaves signed with the public key
> are unconditionally allowed to initialize. [1]
>
> Add FEAT_CTL_SGX_LC_ENABLED, which informs whether the aformentioned MSRs
> are writable or not. If the bit is off, the public key MSRs are read-only
> for the OS.
>
> If the MSRs are read-only, the platform must provide a launch enclave (LE).
> LE can create cryptographic tokens for other enclaves that they can pass
> together with their signature to the ENCLS(EINIT) opcode, which is used
> to initialize enclaves.
>
> Linux is unlikely to support the locked configuration because it takes away
> the control of the launch decisions from the kernel.
>
> [1] Intel SDM: 38.1.4 Intel SGX Launch Control Configuration
>
> Reviewed-by: Borislav Petkov <bp@...en8.de>
> Acked-by: Jethro Beekman <jethro@...tanix.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Co-developed-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

Reviewed-by: Darren Kenny <darren.kenny@...cle.com>

> ---
>  arch/x86/include/asm/cpufeatures.h | 1 +
>  arch/x86/include/asm/msr-index.h   | 7 +++++++
>  2 files changed, 8 insertions(+)
>
> diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
> index 545ac3e0e269..0a4541e4f076 100644
> --- a/arch/x86/include/asm/cpufeatures.h
> +++ b/arch/x86/include/asm/cpufeatures.h
> @@ -352,6 +352,7 @@
>  #define X86_FEATURE_CLDEMOTE		(16*32+25) /* CLDEMOTE instruction */
>  #define X86_FEATURE_MOVDIRI		(16*32+27) /* MOVDIRI instruction */
>  #define X86_FEATURE_MOVDIR64B		(16*32+28) /* MOVDIR64B instruction */
> +#define X86_FEATURE_SGX_LC		(16*32+30) /* Software Guard Extensions Launch Control */
>  
>  /* AMD-defined CPU features, CPUID level 0x80000007 (EBX), word 17 */
>  #define X86_FEATURE_OVERFLOW_RECOV	(17*32+ 0) /* MCA overflow recovery support */
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index 18e08da19f16..3d7c89a8533f 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -582,6 +582,7 @@
>  #define FEAT_CTL_LOCKED				BIT(0)
>  #define FEAT_CTL_VMX_ENABLED_INSIDE_SMX		BIT(1)
>  #define FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX	BIT(2)
> +#define FEAT_CTL_SGX_LC_ENABLED			BIT(17)
>  #define FEAT_CTL_SGX_ENABLED			BIT(18)
>  #define FEAT_CTL_LMCE_ENABLED			BIT(20)
>  
> @@ -602,6 +603,12 @@
>  #define MSR_IA32_UCODE_WRITE		0x00000079
>  #define MSR_IA32_UCODE_REV		0x0000008b
>  
> +/* Intel SGX Launch Enclave Public Key Hash MSRs */
> +#define MSR_IA32_SGXLEPUBKEYHASH0	0x0000008C
> +#define MSR_IA32_SGXLEPUBKEYHASH1	0x0000008D
> +#define MSR_IA32_SGXLEPUBKEYHASH2	0x0000008E
> +#define MSR_IA32_SGXLEPUBKEYHASH3	0x0000008F
> +
>  #define MSR_IA32_SMM_MONITOR_CTL	0x0000009b
>  #define MSR_IA32_SMBASE			0x0000009e
>  
> -- 
> 2.25.1