linux-kernel - [PATCH v4 07/20] KVM:x86: Add fault checks for guest CR4.CET setting

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Date:   Thu, 20 Jul 2023 23:03:39 -0400
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     seanjc@...gle.com, pbonzini@...hat.com, peterz@...radead.org,
        john.allen@....com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     rick.p.edgecombe@...el.com, chao.gao@...el.com,
        binbin.wu@...ux.intel.com, weijiang.yang@...el.com
Subject: [PATCH v4 07/20] KVM:x86: Add fault checks for guest CR4.CET setting

Check potential faults for CR4.CET setting per Intel SDM.
CET can be enabled if and only if CR0.WP==1, i.e. setting
CR4.CET=1 faults if CR0.WP==0 and setting CR0.WP=0 fails
if CR4.CET==1.

Co-developed-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/x86.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 04f0245ad0a2..be76ac6bbb21 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -993,6 +993,9 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
 	    (is_64_bit_mode(vcpu) || kvm_is_cr4_bit_set(vcpu, X86_CR4_PCIDE)))
 		return 1;
 
+	if (!(cr0 & X86_CR0_WP) && kvm_is_cr4_bit_set(vcpu, X86_CR4_CET))
+		return 1;
+
 	static_call(kvm_x86_set_cr0)(vcpu, cr0);
 
 	kvm_post_set_cr0(vcpu, old_cr0, cr0);
@@ -1204,6 +1207,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
 			return 1;
 	}
 
+	if ((cr4 & X86_CR4_CET) && !kvm_is_cr0_bit_set(vcpu, X86_CR0_WP))
+		return 1;
+
 	static_call(kvm_x86_set_cr4)(vcpu, cr4);
 
 	kvm_post_set_cr4(vcpu, old_cr4, cr4);
-- 
2.27.0