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From:   Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To:     x86@kernel.org, linux-sgx@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org,
        Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Darren Kenny <darren.kenny@oracle.com>,
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Subject: [PATCH v40 08/24] x86/cpu/intel: Add nosgx kernel parameter
Date:   Wed,  4 Nov 2020 16:54:14 +0200
Message-Id: <20201104145430.300542-9-jarkko.sakkinen@linux.intel.com>
In-Reply-To: <20201104145430.300542-1-jarkko.sakkinen@linux.intel.com>
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Add kernel parameter to disable Intel SGX kernel support, along with
supporting Documentation.

Tested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.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