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From: isaku.yamahata@intel.com
To: kvm@vger.kernel.org,
	linux-kernel@vger.kernel.org
Cc: isaku.yamahata@intel.com,
	isaku.yamahata@gmail.com,
	Paolo Bonzini <pbonzini@redhat.com>,
	erdemaktas@google.com,
	Sean Christopherson <seanjc@google.com>,
	Sagi Shahar <sagis@google.com>,
	Kai Huang <kai.huang@intel.com>,
	chen.bo@intel.com,
	hang.yuan@intel.com,
	tina.zhang@intel.com
Subject: [PATCH v19 119/130] KVM: TDX: Add methods to ignore guest instruction emulation
Date: Mon, 26 Feb 2024 00:27:01 -0800
Message-Id: <a70ca20449acd995100a52f2a1076a5197cc45da.1708933498.git.isaku.yamahata@intel.com>
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From: Isaku Yamahata <isaku.yamahata@intel.com>

Because TDX protects TDX guest state from VMM, instructions in guest memory
cannot be emulated.  Implement methods to ignore guest instruction
emulator.

Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
 arch/x86/kvm/vmx/main.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index 9fb3f28d8259..9aaa9bd7abf3 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -320,6 +320,30 @@ static void vt_enable_smi_window(struct kvm_vcpu *vcpu)
 }
 #endif
 
+static int vt_check_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
+					void *insn, int insn_len)
+{
+	if (is_td_vcpu(vcpu))
+		return X86EMUL_RETRY_INSTR;
+
+	return vmx_check_emulate_instruction(vcpu, emul_type, insn, insn_len);
+}
+
+static int vt_check_intercept(struct kvm_vcpu *vcpu,
+				 struct x86_instruction_info *info,
+				 enum x86_intercept_stage stage,
+				 struct x86_exception *exception)
+{
+	/*
+	 * This call back is triggered by the x86 instruction emulator. TDX
+	 * doesn't allow guest memory inspection.
+	 */
+	if (KVM_BUG_ON(is_td_vcpu(vcpu), vcpu->kvm))
+		return X86EMUL_UNHANDLEABLE;
+
+	return vmx_check_intercept(vcpu, info, stage, exception);
+}
+
 static bool vt_apic_init_signal_blocked(struct kvm_vcpu *vcpu)
 {
 	if (is_td_vcpu(vcpu))
@@ -976,7 +1000,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 
 	.load_mmu_pgd = vt_load_mmu_pgd,
 
-	.check_intercept = vmx_check_intercept,
+	.check_intercept = vt_check_intercept,
 	.handle_exit_irqoff = vt_handle_exit_irqoff,
 
 	.request_immediate_exit = vt_request_immediate_exit,
@@ -1005,7 +1029,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.enable_smi_window = vt_enable_smi_window,
 #endif
 
-	.check_emulate_instruction = vmx_check_emulate_instruction,
+	.check_emulate_instruction = vt_check_emulate_instruction,
 	.apic_init_signal_blocked = vt_apic_init_signal_blocked,
 	.migrate_timers = vmx_migrate_timers,
 
-- 
2.25.1