[PATCH v15 14/14] KVM: x86: Save/Restore GUEST_SSP to/from SMRAM

[Yang Weijiang]

Save GUEST_SSP to SMRAM when guest exits to SMM due to SMI and restore it
when guest exits SMM to interrupted normal non-root mode.

Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 arch/x86/kvm/emulate.c | 11 +++++++++++
 arch/x86/kvm/x86.c     | 10 ++++++++++
 2 files changed, 21 insertions(+)

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 56cae1ff9e3f..6d4a3181d8bd 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2615,6 +2615,17 @@ static int rsm_load_state_64(struct x86_emulate_ctxt *ctxt,
 			return r;
 	}
 
+	if (kvm_cet_supported()) {
+		struct msr_data msr;
+
+		val = GET_SMSTATE(u64, smstate, 0x7ec8);
+		msr.index = MSR_KVM_GUEST_SSP;
+		msr.host_initiated = true;
+		msr.data = val;
+		/* Mimic host_initiated access to bypass ssp access check. */
+		kvm_x86_ops.set_msr(ctxt->vcpu, &msr);
+	}
+
 	return X86EMUL_CONTINUE;
 }
 #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 22eb6b8626a8..f63b713cd71f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8592,6 +8592,16 @@ static void enter_smm_save_state_64(struct kvm_vcpu *vcpu, char *buf)
 
 	for (i = 0; i < 6; i++)
 		enter_smm_save_seg_64(vcpu, buf, i);
+
+	if (kvm_cet_supported()) {
+		struct msr_data msr;
+
+		msr.index = MSR_KVM_GUEST_SSP;
+		msr.host_initiated = true;
+		/* GUEST_SSP is stored in VMCS at vm-exit. */
+		kvm_x86_ops.get_msr(vcpu, &msr);
+		put_smstate(u64, buf, 0x7ec8, msr.data);
+	}
 }
 #endif
 
-- 
2.26.2