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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>,
        David Matlack <dmatlack@google.com>
Subject: [PATCH v11 104/113] KVM: TDX: Add methods to ignore guest instruction emulation
Date:   Thu, 12 Jan 2023 08:32:52 -0800
Message-Id: <f7e023ff9de85210b69f17098ac0e0fa1cfdc9de.1673539699.git.isaku.yamahata@intel.com>
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References: <cover.1673539699.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 c9d7d8fbd2d7..47c2b6e1e484 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -256,6 +256,30 @@ static void vt_enable_smi_window(struct kvm_vcpu *vcpu)
 }
 #endif
 
+static bool vt_can_emulate_instruction(struct kvm_vcpu *vcpu, int emul_type,
+				       void *insn, int insn_len)
+{
+	if (is_td_vcpu(vcpu))
+		return false;
+
+	return vmx_can_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))
@@ -841,7 +865,7 @@ 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,
@@ -870,7 +894,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.enable_smi_window = vt_enable_smi_window,
 #endif
 
-	.can_emulate_instruction = vmx_can_emulate_instruction,
+	.can_emulate_instruction = vt_can_emulate_instruction,
 	.apic_init_signal_blocked = vt_apic_init_signal_blocked,
 	.migrate_timers = vmx_migrate_timers,
 
-- 
2.25.1