linux-kernel - [PATCH v3 11/10] [NOT TO COMMIT] KVM: TDX: put somewhat sensible values in vCPU for encrypted registers

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Message-ID: <20250307212053.2948340-12-pbonzini@redhat.com>
Date: Fri,  7 Mar 2025 16:20:53 -0500
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: xiaoyao.li@...el.com,
	adrian.hunter@...el.com,
	seanjc@...gle.com,
	rick.p.edgecombe@...el.com
Subject: [PATCH v3 11/10] [NOT TO COMMIT] KVM: TDX: put somewhat sensible values in vCPU for encrypted registers

This shows the hunks that were *removed* from v2 without a replacement;
it's not in kvm-coco-queue.

Originally from a patch by Isaku Yamahata and Adrian Hunter.

Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/vmx/tdx.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index c0fcd0508264..904f8f656394 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2005,9 +2005,23 @@ static int tdx_vcpu_get_cpuid(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd)
 	return r;
 }
 
+static u64 tdx_guest_cr0(struct kvm_vcpu *vcpu, u64 cr4)
+{
+	u64 cr0 = ~CR0_RESERVED_BITS;
+
+	if (cr4 & X86_CR4_CET)
+		cr0 |= X86_CR0_WP;
+
+	cr0 |= X86_CR0_PE | X86_CR0_NE;
+	cr0 &= ~(X86_CR0_NW | X86_CR0_CD);
+
+	return cr0;
+}
+
 static int tdx_vcpu_init(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd)
 {
 	u64 apic_base;
+	struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
 	struct vcpu_tdx *tdx = to_tdx(vcpu);
 	int ret;
 
@@ -2030,6 +2044,18 @@ static int tdx_vcpu_init(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd)
 	if (ret)
 		return ret;
 
+	/*
+	 * Just stuff something sensible in vcpu->arch.  Note that all runtime
+	 * access to CRn and XCR0 is blocked by guest_state_protected.
+	 */
+	vcpu->arch.cr4 = ~vcpu->arch.cr4_guest_rsvd_bits;
+	vcpu->arch.cr0 = tdx_guest_cr0(vcpu, vcpu->arch.cr4);
+	vcpu->arch.ia32_xss = kvm_tdx->xfam & kvm_caps.supported_xss;
+	vcpu->arch.xcr0 = kvm_tdx->xfam & kvm_caps.supported_xcr0;
+
+	/* TODO: freeze vCPU model before kvm_update_cpuid_runtime() */
+	kvm_update_cpuid_runtime(vcpu);
+
 	tdx->state = VCPU_TD_STATE_INITIALIZED;
 
 	return 0;
-- 
2.43.5