The following commit has been merged into the x86/urgent branch of tip: Commit-ID: baf6a4fdb5ead6be10aa0a0e620d6078a669fc75 Gitweb: https://git.kernel.org/tip/baf6a4fdb5ead6be10aa0a0e620d6078a669fc75 Author: Vladis Dronov <vdronov@xxxxxxxxxx> AuthorDate: Sun, 09 Mar 2025 18:22:16 +01:00 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Mon, 10 Mar 2025 09:40:38 +01:00 x86/sgx: Warn explicitly if X86_FEATURE_SGX_LC is not enabled The kernel requires X86_FEATURE_SGX_LC to be able to create SGX enclaves, not just X86_FEATURE_SGX. There is quite a number of hardware which has X86_FEATURE_SGX but not X86_FEATURE_SGX_LC. A kernel running on such hardware does not create the /dev/sgx_enclave file and does so silently. Explicitly warn if X86_FEATURE_SGX_LC is not enabled to properly notify users that the kernel disabled the SGX driver. The X86_FEATURE_SGX_LC, a.k.a. SGX Launch Control, is a CPU feature that enables LE (Launch Enclave) hash MSRs to be writable (with additional opt-in required in the 'feature control' MSR) when running enclaves, i.e. using a custom root key rather than the Intel proprietary key for enclave signing. I've hit this issue myself and have spent some time researching where my /dev/sgx_enclave file went on SGX-enabled hardware. Related links: https://github.com/intel/linux-sgx/issues/837 https://patchwork.kernel.org/project/platform-driver-x86/patch/20180827185507.17087-3-jarkko.sakkinen@xxxxxxxxxxxxxxx/ [ mingo: Made the error message a bit more verbose, and added other cases where the kernel fails to create the /dev/sgx_enclave device node. ] Signed-off-by: Vladis Dronov <vdronov@xxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Acked-by: Kai Huang <kai.huang@xxxxxxxxx> Cc: Jarkko Sakkinen <jarkko@xxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20250309172215.21777-2-vdronov@xxxxxxxxxx --- arch/x86/kernel/cpu/sgx/driver.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c index 22b65a5..40c3347 100644 --- a/arch/x86/kernel/cpu/sgx/driver.c +++ b/arch/x86/kernel/cpu/sgx/driver.c @@ -150,13 +150,15 @@ int __init sgx_drv_init(void) u64 xfrm_mask; int ret; - if (!cpu_feature_enabled(X86_FEATURE_SGX_LC)) + if (!cpu_feature_enabled(X86_FEATURE_SGX_LC)) { + pr_err("SGX disabled: SGX launch control CPU feature is not available, /dev/sgx_enclave disabled.\n"); return -ENODEV; + } cpuid_count(SGX_CPUID, 0, &eax, &ebx, &ecx, &edx); if (!(eax & 1)) { - pr_err("SGX disabled: SGX1 instruction support not available.\n"); + pr_err("SGX disabled: SGX1 instruction support not available, /dev/sgx_enclave disabled.\n"); return -ENODEV; } @@ -173,8 +175,10 @@ int __init sgx_drv_init(void) } ret = misc_register(&sgx_dev_enclave); - if (ret) + if (ret) { + pr_err("SGX disabled: Unable to register the /dev/sgx_enclave driver (%d).\n", ret); return ret; + } return 0; }
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