linux-kernel - [PATCH v11 109/113] KVM: TDX: Add a method to ignore for TDX to ignore hypercall patch

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Message-Id: <5140cd4ba6803ea7de4437ded2c58637106adff5.1673539699.git.isaku.yamahata@intel.com>
Date:   Thu, 12 Jan 2023 08:32:57 -0800
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: [PATCH v11 109/113] KVM: TDX: Add a method to ignore for TDX to ignore hypercall patch

From: Isaku Yamahata <isaku.yamahata@...el.com>

Because guest TD memory is protected, VMM patching guest binary for
hypercall instruction isn't possible.  Add a method to ignore hypercall
patching with a warning.  Note: guest TD kernel needs to be modified to use
TDG.VP.VMCALL for hypercall.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/kvm/vmx/main.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
index b4d1cc3736a6..994ead1b6788 100644
--- a/arch/x86/kvm/vmx/main.c
+++ b/arch/x86/kvm/vmx/main.c
@@ -642,6 +642,19 @@ static u32 vt_get_interrupt_shadow(struct kvm_vcpu *vcpu)
 	return vmx_get_interrupt_shadow(vcpu);
 }
 
+static void vt_patch_hypercall(struct kvm_vcpu *vcpu,
+				  unsigned char *hypercall)
+{
+	/*
+	 * Because guest memory is protected, guest can't be patched. TD kernel
+	 * is modified to use TDG.VP.VMCAL for hypercall.
+	 */
+	if (KVM_BUG_ON(is_td_vcpu(vcpu), vcpu->kvm))
+		return;
+
+	vmx_patch_hypercall(vcpu, hypercall);
+}
+
 static void vt_inject_irq(struct kvm_vcpu *vcpu, bool reinjected)
 {
 	if (is_td_vcpu(vcpu))
@@ -895,7 +908,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.update_emulated_instruction = vmx_update_emulated_instruction,
 	.set_interrupt_shadow = vt_set_interrupt_shadow,
 	.get_interrupt_shadow = vt_get_interrupt_shadow,
-	.patch_hypercall = vmx_patch_hypercall,
+	.patch_hypercall = vt_patch_hypercall,
 	.inject_irq = vt_inject_irq,
 	.inject_nmi = vt_inject_nmi,
 	.inject_exception = vt_inject_exception,
-- 
2.25.1