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authorSean Christopherson <sean.j.christopherson@intel.com>2020-03-12 11:04:16 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2020-03-14 10:34:51 +0100
commit7a57c09bb1cb89239f38f690b87cdf2c7db76c34 (patch)
tree6175a9774897b559c8588ed8ca0355034290e60a /arch
parenta754acc3e4bcf0b70f4356fc450fec72875762da (diff)
KVM: VMX: Condition ENCLS-exiting enabling on CPU support for SGX1
Enable ENCLS-exiting (and thus set vmcs.ENCLS_EXITING_BITMAP) only if the CPU supports SGX1. Per Intel's SDM, all ENCLS leafs #UD if SGX1 is not supported[*], i.e. intercepting ENCLS to inject a #UD is unnecessary. Avoiding ENCLS-exiting even when it is reported as supported by the CPU works around a reported issue where SGX is "hard" disabled after an S3 suspend/resume cycle, i.e. CPUID.0x7.SGX=0 and the VMCS field/control are enumerated as unsupported. While the root cause of the S3 issue is unknown, it's definitely _not_ a KVM (or kernel) bug, i.e. this is a workaround for what is most likely a hardware or firmware issue. As a bonus side effect, KVM saves a VMWRITE when first preparing vmcs01 and vmcs02. Note, SGX must be disabled in BIOS to take advantage of this workaround [*] The additional ENCLS CPUID check on SGX1 exists so that SGX can be globally "soft" disabled post-reset, e.g. if #MC bits in MCi_CTL are cleared. Soft disabled meaning disabling SGX without clearing the primary CPUID bit (in leaf 0x7) and without poking into non-SGX CPU paths, e.g. for the VMCS controls. Fixes: 0b665d304028 ("KVM: vmx: Inject #UD for SGX ENCLS instruction in guest") Reported-by: Toni Spets <toni.spets@iki.fi> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/vmx/vmx.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 40b1e6138cd5..26f8f31563e9 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2338,6 +2338,17 @@ static void hardware_disable(void)
kvm_cpu_vmxoff();
}
+/*
+ * There is no X86_FEATURE for SGX yet, but anyway we need to query CPUID
+ * directly instead of going through cpu_has(), to ensure KVM is trapping
+ * ENCLS whenever it's supported in hardware. It does not matter whether
+ * the host OS supports or has enabled SGX.
+ */
+static bool cpu_has_sgx(void)
+{
+ return cpuid_eax(0) >= 0x12 && (cpuid_eax(0x12) & BIT(0));
+}
+
static __init int adjust_vmx_controls(u32 ctl_min, u32 ctl_opt,
u32 msr, u32 *result)
{
@@ -2418,8 +2429,9 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE |
SECONDARY_EXEC_PT_USE_GPA |
SECONDARY_EXEC_PT_CONCEAL_VMX |
- SECONDARY_EXEC_ENABLE_VMFUNC |
- SECONDARY_EXEC_ENCLS_EXITING;
+ SECONDARY_EXEC_ENABLE_VMFUNC;
+ if (cpu_has_sgx())
+ opt2 |= SECONDARY_EXEC_ENCLS_EXITING;
if (adjust_vmx_controls(min2, opt2,
MSR_IA32_VMX_PROCBASED_CTLS2,
&_cpu_based_2nd_exec_control) < 0)