linux-kernel - [PATCH v3] KVM: nVMX: Advertise ENCLS_EXITING to L1 iff SGX is fully supported

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Date:   Wed, 26 Oct 2022 03:23:30 -0400
From:   Emanuele Giuseppe Esposito <eesposit@...hat.com>
To:     kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Bandan Das <bsd@...hat.com>,
        linux-kernel@...r.kernel.org,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        stable@...r.kernel.org
Subject: [PATCH v3] KVM: nVMX: Advertise ENCLS_EXITING to L1 iff SGX is fully supported

Clear enable_sgx if ENCLS-exiting is not supported, i.e. if SGX cannot be
virtualized.  This fixes a bug where KVM would advertise ENCLS-exiting to
L1 and propagate the control from vmcs12 to vmcs02 even if ENCLS-exiting
isn't supported in secondary execution controls, e.g. because SGX isn't
fully enabled, and thus induce an unexpected VM-Fail in L1.

Not updating enable_sgx is responsible for a second bug:
vmx_set_cpu_caps() doesn't clear the SGX bits when hardware support is
unavailable.  This is a much less problematic bug as it only pops up
if SGX is soft-disabled (the case being handled by cpu_has_sgx()) or if
SGX is supported for bare metal but not in the VMCS (will never happen
when running on bare metal, but can theoertically happen when running in
a VM).

Last but not least, KVM should ideally have module params reflect KVM's
actual configuration.

RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=2127128

Fixes: 72add915fbd5 ("KVM: VMX: Enable SGX virtualization for SGX1, SGX2 and LC")
Cc: stable@...r.kernel.org

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Suggested-by: Bandan Das <bsd@...hat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 9dba04b6b019..ea0c65d3c08a 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -8263,6 +8263,11 @@ static __init int hardware_setup(void)
 	if (!cpu_has_virtual_nmis())
 		enable_vnmi = 0;

+	#ifdef CONFIG_X86_SGX_KVM
+		if (!cpu_has_vmx_encls_vmexit())
+			enable_sgx = false;
+	#endif
+
 	/*
 	 * set_apic_access_page_addr() is used to reload apic access
 	 * page upon invalidation.  No need to do anything if not
-- 
2.31.1