linux-kernel - [PATCH v2 22/28] KVM: VMX: Clear controls obsoleted by EPT at runtime, not setup

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Date:   Wed, 29 Jun 2022 17:06:19 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 22/28] KVM: VMX: Clear controls obsoleted by EPT at runtime, not setup

From: Sean Christopherson <seanjc@...gle.com>

Clear the CR3 and INVLPG interception controls at runtime based on
whether or not EPT is being _used_, as opposed to clearing the bits at
setup if EPT is _supported_ in hardware, and then restoring them when EPT
is not used.  Not mucking with the base config will allow using the base
config as the starting point for emulating the VMX capability MSRs.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/vmx/vmx.c | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e5e4383d0cff..fb58b0be953d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -2501,13 +2501,8 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
 	rdmsr_safe(MSR_IA32_VMX_EPT_VPID_CAP,
 		&vmx_cap->ept, &vmx_cap->vpid);
 
-	if (_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_EPT) {
-		/* CR3 accesses and invlpg don't need to cause VM Exits when EPT
-		   enabled */
-		_cpu_based_exec_control &= ~(CPU_BASED_CR3_LOAD_EXITING |
-					     CPU_BASED_CR3_STORE_EXITING |
-					     CPU_BASED_INVLPG_EXITING);
-	} else if (vmx_cap->ept) {
+	if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_EPT) &&
+	    vmx_cap->ept) {
 		pr_warn_once("EPT CAP should not exist if not support "
 				"1-setting enable EPT VM-execution control\n");
 
@@ -4268,10 +4263,11 @@ static u32 vmx_exec_control(struct vcpu_vmx *vmx)
 		exec_control |= CPU_BASED_CR8_STORE_EXITING |
 				CPU_BASED_CR8_LOAD_EXITING;
 #endif
-	if (!enable_ept)
-		exec_control |= CPU_BASED_CR3_STORE_EXITING |
-				CPU_BASED_CR3_LOAD_EXITING  |
-				CPU_BASED_INVLPG_EXITING;
+	/* No need to intercept CR3 access or INVPLG when using EPT. */
+	if (enable_ept)
+		exec_control &= ~(CPU_BASED_CR3_LOAD_EXITING |
+				  CPU_BASED_CR3_STORE_EXITING |
+				  CPU_BASED_INVLPG_EXITING);
 	if (kvm_mwait_in_guest(vmx->vcpu.kvm))
 		exec_control &= ~(CPU_BASED_MWAIT_EXITING |
 				CPU_BASED_MONITOR_EXITING);
-- 
2.35.3