linux-kernel - [PATCH 2/2] KVM: VMX: Fix VPID capability detection

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Date:   Sat, 14 Oct 2017 19:31:37 -0700
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: [PATCH 2/2] KVM: VMX: Fix VPID capability detection

From: Wanpeng Li <wanpeng.li@...mail.com>

According to the Intel SDM, volume 3, section 28.3.2: Creating and
Using Cached Translation Information, "The following items describe the 
creation of mappings while EPT is not in use":
 - Linear mappings may be created. They are derived from the paging 
   structures referenced (directly or indirectly) by the current value 
   of CR3 and are associated with the current VPID and the current PCID.

The VPID is used to tag linear mappings when EPT is not enabled. However,
current logic just detects VPID capability if EPT is enabled, this patch 
fixes it.

Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
---
 arch/x86/kvm/vmx.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3644540..800d08c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3681,15 +3681,19 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf)
 				SECONDARY_EXEC_VIRTUALIZE_X2APIC_MODE |
 				SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY);
 
+	rdmsr(MSR_IA32_VMX_EPT_VPID_CAP,
+		vmx_capability.ept, vmx_capability.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);
-		rdmsr(MSR_IA32_VMX_EPT_VPID_CAP,
-		      vmx_capability.ept, vmx_capability.vpid);
-	}
+	} else
+		vmx_capability.ept = 0;
+	if (!(_cpu_based_2nd_exec_control & SECONDARY_EXEC_ENABLE_VPID))
+		vmx_capability.vpid = 0;
 
 	min = VM_EXIT_SAVE_DEBUG_CONTROLS | VM_EXIT_ACK_INTR_ON_EXIT;
 #ifdef CONFIG_X86_64
-- 
2.7.4