linux-kernel - [PATCH v40 08/24] x86/cpu/intel: Add nosgx kernel parameter

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Date:   Wed,  4 Nov 2020 16:54:14 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     x86@...nel.org, linux-sgx@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Darren Kenny <darren.kenny@...cle.com>,
        akpm@...ux-foundation.org, andriy.shevchenko@...ux.intel.com,
        asapek@...gle.com, bp@...en8.de, cedric.xing@...el.com,
        chenalexchen@...gle.com, conradparker@...gle.com,
        cyhanish@...gle.com, dave.hansen@...el.com, haitao.huang@...el.com,
        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, mikko.ylinen@...el.com
Subject: [PATCH v40 08/24] x86/cpu/intel: Add nosgx kernel parameter

Add kernel parameter to disable Intel SGX kernel support, along with
supporting Documentation.

Tested-by: Sean Christopherson <sean.j.christopherson@...el.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@...el.com>
Reviewed-by: Darren Kenny <darren.kenny@...cle.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 2 ++
 arch/x86/kernel/cpu/feat_ctl.c                  | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index bd1a5b87a5e2..4684611edf09 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3385,6 +3385,8 @@
 
 	nosep		[BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
 
+	nosgx		[X86-64,SGX] Disables Intel SGX kernel support.
+
 	nosmp		[SMP] Tells an SMP kernel to act as a UP kernel,
 			and disable the IO APIC.  legacy for "maxcpus=0".
 
diff --git a/arch/x86/kernel/cpu/feat_ctl.c b/arch/x86/kernel/cpu/feat_ctl.c
index d38e97325018..3b1b01f2b248 100644
--- a/arch/x86/kernel/cpu/feat_ctl.c
+++ b/arch/x86/kernel/cpu/feat_ctl.c
@@ -99,6 +99,15 @@ static void clear_sgx_caps(void)
 	setup_clear_cpu_cap(X86_FEATURE_SGX_LC);
 }
 
+static int __init nosgx(char *str)
+{
+	clear_sgx_caps();
+
+	return 0;
+}
+
+early_param("nosgx", nosgx);
+
 void init_ia32_feat_ctl(struct cpuinfo_x86 *c)
 {
 	bool tboot = tboot_enabled();
-- 
2.27.0