linux-kernel - [PATCH v3 2/2] KVM: VMX: Don't expose unrestricted

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Date:   Mon,  9 Oct 2017 15:51:53 -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>,
        Jim Mattson <jmattson@...gle.com>
Subject: [PATCH v3 2/2] KVM: VMX: Don't expose unrestricted_guest is enabled if ept is disabled

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

SDM mentioned:

 "If either the “unrestricted guest” VM-execution control or the “mode-based
  execute control for EPT” VM- execution control is 1, the “enable EPT”
  VM-execution control must also be 1."

However, we can still observe unrestricted_guest is Y after inserting the kvm-intel.ko
w/ ept=N. It depends on later starts a guest in order that the function
vmx_compute_secondary_exec_control() can be executed, then both the module parameter
and exec control fields will be amended.

This patch fixes it by amending module parameter immediately during vmcs data setup.

Reviewed-by: Jim Mattson <jmattson@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Radim Krčmář <rkrcmar@...hat.com>
Cc: Jim Mattson <jmattson@...gle.com>
Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
---
v1 -> v2: 
 * reduce to just "enable_ept = 0"

 arch/x86/kvm/vmx.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ab0f16e..dedff59 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6730,16 +6730,13 @@ static __init int hardware_setup(void)
 	if (!cpu_has_vmx_ept() ||
 	    !cpu_has_vmx_ept_4levels() ||
 	    !cpu_has_vmx_ept_mt_wb() ||
-	    !cpu_has_vmx_invept_global()) {
+	    !cpu_has_vmx_invept_global())
 		enable_ept = 0;
-		enable_unrestricted_guest = 0;
-		enable_ept_ad_bits = 0;
-	}
 
 	if (!cpu_has_vmx_ept_ad_bits() || !enable_ept)
 		enable_ept_ad_bits = 0;
 
-	if (!cpu_has_vmx_unrestricted_guest())
+	if (!cpu_has_vmx_unrestricted_guest() || !enable_ept)
 		enable_unrestricted_guest = 0;
 
 	if (!cpu_has_vmx_flexpriority())
-- 
2.7.4