From: Vladis Dronov vdronov@redhat.com
[ Upstream commit 65be5c95d08eedda570a6c888a12384c77fe7614 ]
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/2018082718550...
[ 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@redhat.com Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: Kai Huang kai.huang@intel.com Cc: Jarkko Sakkinen jarkko@kernel.org Cc: Andy Lutomirski luto@kernel.org Cc: Sean Christopherson sean.j.christopherson@intel.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Link: https://lore.kernel.org/r/20250309172215.21777-2-vdronov@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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 22b65a5f5ec6c..7f8d1e11dbee2 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_info("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_info("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_info("SGX disabled: Unable to register the /dev/sgx_enclave driver (%d).\n", ret); return ret; + }
return 0; }