diff mbox series

[05/10] KVM: allow compiling out SMM support

Message ID 20221027164944.3031588-6-pbonzini@redhat.com (mailing list archive)
State New, archived
Headers show
Series KVM: x86: allow compiling out SMM support | expand

Commit Message

Paolo Bonzini Oct. 27, 2022, 4:49 p.m. UTC 
Some users of KVM implement the UEFI variable store through a paravirtual device
that does not require the "SMM lockbox" component of edk2; allow them to
compile out system management mode, which is not a full implementation
especially in how it interacts with nested virtualization.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20220929172016.319443-6-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/Kconfig                          | 11 ++++++++++
 arch/x86/kvm/Makefile                         |  2 +-
 arch/x86/kvm/smm.h                            | 12 ++++++++++
 arch/x86/kvm/svm/svm.c                        |  2 ++
 arch/x86/kvm/vmx/vmx.c                        |  2 ++
 arch/x86/kvm/x86.c                            | 22 +++++++++++++++++--
 tools/testing/selftests/kvm/x86_64/smm_test.c |  2 ++
 7 files changed, 50 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 67be7f217e37..fbeaa9ddef59 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -118,6 +118,17 @@  config KVM_AMD_SEV
 	  Provides support for launching Encrypted VMs (SEV) and Encrypted VMs
 	  with Encrypted State (SEV-ES) on AMD processors.
 
+config KVM_SMM
+	bool "System Management Mode emulation"
+	default y
+	depends on KVM
+	help
+	  Provides support for KVM to emulate System Management Mode (SMM)
+	  in virtual machines.  This can be used by the virtual machine
+	  firmware to implement UEFI secure boot.
+
+	  If unsure, say Y.
+
 config KVM_XEN
 	bool "Support for Xen hypercall interface"
 	depends on KVM
diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
index ec6f7656254b..6cf40f668277 100644
--- a/arch/x86/kvm/Makefile
+++ b/arch/x86/kvm/Makefile
@@ -20,7 +20,7 @@  endif
 
 kvm-$(CONFIG_X86_64) += mmu/tdp_iter.o mmu/tdp_mmu.o
 kvm-$(CONFIG_KVM_XEN)	+= xen.o
-kvm-y			+= smm.o
+kvm-$(CONFIG_KVM_SMM)	+= smm.o
 
 kvm-intel-y		+= vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
 			   vmx/evmcs.o vmx/nested.o vmx/posted_intr.o
diff --git a/arch/x86/kvm/smm.h b/arch/x86/kvm/smm.h
index b0602a92e511..0e1bd8bd6dc4 100644
--- a/arch/x86/kvm/smm.h
+++ b/arch/x86/kvm/smm.h
@@ -8,6 +8,7 @@ 
 #define PUT_SMSTATE(type, buf, offset, val)                      \
 	*(type *)((buf) + (offset) - 0x7e00) = val
 
+#ifdef CONFIG_KVM_SMM
 static inline int kvm_inject_smi(struct kvm_vcpu *vcpu)
 {
 	kvm_make_request(KVM_REQ_SMI, vcpu);
@@ -23,5 +24,16 @@  void kvm_smm_changed(struct kvm_vcpu *vcpu, bool in_smm);
 void enter_smm(struct kvm_vcpu *vcpu);
 int emulator_leave_smm(struct x86_emulate_ctxt *ctxt);
 void process_smi(struct kvm_vcpu *vcpu);
+#else
+static inline int kvm_inject_smi(struct kvm_vcpu *vcpu) { return -ENOTTY; }
+static inline bool is_smm(struct kvm_vcpu *vcpu) { return false; }
+static inline void enter_smm(struct kvm_vcpu *vcpu) { WARN_ON_ONCE(1); }
+static inline void process_smi(struct kvm_vcpu *vcpu) { WARN_ON_ONCE(1); }
+
+/*
+ * emulator_leave_smm is used as a function pointer, so the
+ * stub is defined in x86.c.
+ */
+#endif
 
 #endif
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 496ee7d1ae2f..6f7ceb35d2ff 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4150,6 +4150,8 @@  static bool svm_has_emulated_msr(struct kvm *kvm, u32 index)
 	case MSR_IA32_VMX_BASIC ... MSR_IA32_VMX_VMFUNC:
 		return false;
 	case MSR_IA32_SMBASE:
+		if (!IS_ENABLED(CONFIG_KVM_SMM))
+			return false;
 		/* SEV-ES guests do not support SMM, so report false */
 		if (kvm && sev_es_guest(kvm))
 			return false;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index b459ddf30abd..c2abe62d7cc0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6841,6 +6841,8 @@  static bool vmx_has_emulated_msr(struct kvm *kvm, u32 index)
 {
 	switch (index) {
 	case MSR_IA32_SMBASE:
+		if (!IS_ENABLED(CONFIG_KVM_SMM))
+			return false;
 		/*
 		 * We cannot do SMM unless we can run the guest in big
 		 * real mode.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ec5e9a837a12..3ec3d3632316 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3641,7 +3641,7 @@  int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		break;
 	}
 	case MSR_IA32_SMBASE:
-		if (!msr_info->host_initiated)
+		if (!IS_ENABLED(CONFIG_KVM_SMM) || !msr_info->host_initiated)
 			return 1;
 		vcpu->arch.smbase = data;
 		break;
@@ -4057,7 +4057,7 @@  int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		msr_info->data = vcpu->arch.ia32_misc_enable_msr;
 		break;
 	case MSR_IA32_SMBASE:
-		if (!msr_info->host_initiated)
+		if (!IS_ENABLED(CONFIG_KVM_SMM) || !msr_info->host_initiated)
 			return 1;
 		msr_info->data = vcpu->arch.smbase;
 		break;
@@ -4431,6 +4431,9 @@  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 			r |= KVM_X86_DISABLE_EXITS_MWAIT;
 		break;
 	case KVM_CAP_X86_SMM:
+		if (!IS_ENABLED(CONFIG_KVM_SMM))
+			break;
+
 		/* SMBASE is usually relocated above 1M on modern chipsets,
 		 * and SMM handlers might indeed rely on 4G segment limits,
 		 * so do not report SMM to be available if real mode is
@@ -5181,6 +5184,7 @@  static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 		vcpu->arch.apic->sipi_vector = events->sipi_vector;
 
 	if (events->flags & KVM_VCPUEVENT_VALID_SMM) {
+#ifdef CONFIG_KVM_SMM
 		if (!!(vcpu->arch.hflags & HF_SMM_MASK) != events->smi.smm) {
 			kvm_x86_ops.nested_ops->leave_nested(vcpu);
 			kvm_smm_changed(vcpu, events->smi.smm);
@@ -5195,6 +5199,12 @@  static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 				vcpu->arch.hflags &= ~HF_SMM_INSIDE_NMI_MASK;
 		}
 
+#else
+		if (events->smi.smm || events->smi.pending ||
+		    events->smi.smm_inside_nmi)
+			return -EINVAL;
+#endif
+
 		if (lapic_in_kernel(vcpu)) {
 			if (events->smi.latched_init)
 				set_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
@@ -8120,6 +8130,14 @@  static unsigned emulator_get_hflags(struct x86_emulate_ctxt *ctxt)
 	return emul_to_vcpu(ctxt)->arch.hflags;
 }
 
+#ifndef CONFIG_KVM_SMM
+static int emulator_leave_smm(struct x86_emulate_ctxt *ctxt)
+{
+	WARN_ON_ONCE(1);
+	return X86EMUL_UNHANDLEABLE;
+}
+#endif
+
 static void emulator_triple_fault(struct x86_emulate_ctxt *ctxt)
 {
 	kvm_make_request(KVM_REQ_TRIPLE_FAULT, emul_to_vcpu(ctxt));
diff --git a/tools/testing/selftests/kvm/x86_64/smm_test.c b/tools/testing/selftests/kvm/x86_64/smm_test.c
index 1f136a81858e..cb38a478e1f6 100644
--- a/tools/testing/selftests/kvm/x86_64/smm_test.c
+++ b/tools/testing/selftests/kvm/x86_64/smm_test.c
@@ -137,6 +137,8 @@  int main(int argc, char *argv[])
 	struct kvm_x86_state *state;
 	int stage, stage_reported;
 
+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_X86_SMM));
+
 	/* Create VM */
 	vm = vm_create_with_one_vcpu(&vcpu, guest_code);