linux-kernel - [PATCH 08/29] KVM: x86/mmu: Do not enable page track for TD guest

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Message-ID: <20250226195529.2314580-9-pbonzini@redhat.com>
Date: Wed, 26 Feb 2025 14:55:08 -0500
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Cc: seanjc@...gle.com,
	Yan Zhao <yan.y.zhao@...el.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Binbin Wu <binbin.wu@...ux.intel.com>,
	Yuan Yao <yuan.yao@...ux.intel.com>
Subject: [PATCH 08/29] KVM: x86/mmu: Do not enable page track for TD guest

From: Yan Zhao <yan.y.zhao@...el.com>

Fail kvm_page_track_write_tracking_enabled() if VM type is TDX to make the
external page track user fail in kvm_page_track_register_notifier() since
TDX does not support write protection and hence page track.

No need to fail KVM internal users of page track (i.e. for shadow page),
because TDX is always with EPT enabled and currently TDX module does not
emulate and send VMLAUNCH/VMRESUME VMExits to VMM.

Suggested-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: Yuan Yao <yuan.yao@...ux.intel.com>
Message-ID: <20241112073515.22028-1-yan.y.zhao@...el.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
 arch/x86/kvm/mmu/page_track.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c
index 561c331fd6ec..1b17b12393a8 100644
--- a/arch/x86/kvm/mmu/page_track.c
+++ b/arch/x86/kvm/mmu/page_track.c
@@ -172,6 +172,9 @@ static int kvm_enable_external_write_tracking(struct kvm *kvm)
 	struct kvm_memory_slot *slot;
 	int r = 0, i, bkt;
 
+	if (kvm->arch.vm_type == KVM_X86_TDX_VM)
+		return -EOPNOTSUPP;
+
 	mutex_lock(&kvm->slots_arch_lock);
 
 	/*
-- 
2.43.5